ANODE CATALYST MATERIALS FOR ELECTROCHEMICAL CELLS
20220407086 · 2022-12-22
Inventors
- Soo KIM (Arlington, MA, US)
- Ulrich Berner (Stuttgart, DE)
- Charles Tuffile (Swansea, MA, US)
- Mordechai Kornbluth (Brighton, MA, US)
Cpc classification
International classification
Abstract
An anode catalyst layer of an electrochemical cell includes an anode catalyst material. The anode catalyst material is a Pt-based alloy. The Pt-based alloy is a binary Pt-M alloy, where M is Ge, Se, Ag, Sb, Os, or Tl. The Pt-based alloy is a ternary Pt-M.sup.I-M.sup.II alloy, where M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
Claims
1. An anode catalyst layer of an electrochemical cell comprising: an anode catalyst material, the anode catalyst material being a Pt-based alloy, the Pt-based alloy being a binary Pt-M alloy, where M is Ge, Se, Ag, Sb, Os, or Tl.
2. The anode catalyst layer of the electrochemical cell of claim 1, wherein the binary Pt-M alloy is Pt.sub.xM.sub.y, where x=2y, x>0, and M is Ge, Se, Ag, Sb, Os, or Tl.
3. The anode catalyst layer of the electrochemical cell of claim 1, wherein the binary Pt-M alloy is Pt.sub.0.95M.sub.0.05, where M is Ge, Se, Ag, Sb, Os, or Tl.
4. The anode catalyst layer of the electrochemical cell of claim 1, wherein the binary Pt-M alloy is Pt.sub.0.5M.sub.0.5, where M is Ge, Se, Ag, Sb, Os, or Tl.
5. The anode catalyst layer of the electrochemical cell of claim 1, wherein the binary Pt-M alloy is mixed with Ir, Ru, an Ir—Ru alloy, IrO.sub.2, RuO.sub.2, and/or Ir—Ru—O.
6. The anode catalyst layer of the electrochemical cell of claim 1, wherein the binary Pt-M alloy is a nanoparticle having an average size in a range of 1 to 20 nm.
7. An anode catalyst layer of an electrochemical cell comprising: an anode catalyst material, the anode catalyst material being a Pt-based alloy, the Pt-based alloy being a ternary Pt-M.sup.I-M.sup.II alloy, where M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
8. The anode catalyst layer of the electrochemical cell of claim 7, wherein the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=2y=6z, x>0, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
9. The anode catalyst layer of the electrochemical cell of claim 7, wherein the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=6y=2z, x>0, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
10. The anode catalyst layer of the electrochemical cell of claim 7, wherein the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x+y+z=1, 0<x<0.5, 0<y<0.5, 0<z<0.5, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
11. The anode catalyst layer of the electrochemical cell of claim 7, wherein the ternary Pt-M.sup.I-M.sup.II alloy is mixed with Ir, Ru, an Ir—Ru alloy, IrO.sub.2, RuO.sub.2, and/or Ir—Ru—O.
12. The anode catalyst layer of the electrochemical cell of claim 7, wherein the Pt-based alloy is a nanoparticle having an average size in a range of 1 to 20 nm.
13. An electrochemical cell comprising: an anode catalyst layer having an anode catalyst material, the anode catalyst material being a Pt-based alloy, the Pt-based alloy being a binary Pt-M alloy, where M is Ge, Se, Ag, Sb, Os or Tl; or being a ternary Pt-M.sup.I-M.sup.II alloy, where M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd; a cathode catalyst layer; and an electrolyte membrane situated between the anode and cathode catalyst layers.
14. The electrochemical cell of claim 13, wherein the binary Pt-M alloy is Pt.sub.xM.sub.y, where x=2y, x>0, and M is Ge, Se, Ag, Sb, Os, or Tl.
15. The electrochemical cell of claim 13, wherein the binary Pt-M alloy is Pt.sub.0.95M.sub.0.05, where M is Ge, Se, Ag, Sb, Os, or Tl.
16. The electrochemical cell of claim 13, wherein the binary Pt-M alloy is Pt.sub.0.5M.sub.0.5, where M is Ge, Se, Ag, Sb, Os, or Tl.
17. The electrochemical cell of claim 13, wherein the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=2y=6z, x>0, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
18. The electrochemical cell of claim 13, wherein the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=6y=2z, x>0, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
19. The electrochemical cell of claim 13, wherein the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x+y+z=1, 0<x<0.5, 0<y<0.5, 0<z<0.5, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
20. The electrochemical cell of claim 13, wherein the Pt-based alloy is mixed with Ir, Ru, an Ir—Ru alloy, IrO.sub.2, RuO.sub.2, and/or Ir—Ru—O.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0007]
[0008]
[0009]
[0010]
[0011]
DETAILED DESCRIPTION
[0012] Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for applications or implementations.
[0013] This present disclosure is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing embodiments of the present disclosure and is not intended to be limiting in any way.
[0014] As used in the specification and the appended claims, the singular form “a,” “an,” and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components.
[0015] The description of a group or class of materials as suitable for a given purpose in connection with one or more embodiments implies that mixtures of any two or more of the members of the group or class are suitable. Description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description and does not necessarily preclude chemical interactions among constituents of the mixture once mixed.
[0016] Except where expressly indicated, all numerical quantities in this description indicating dimensions or material properties are to be understood as modified by the word “about” in describing the broadest scope of the present disclosure.
[0017] The first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation. Unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.
[0018] The term “substantially” may be used herein to describe disclosed or claimed embodiments. The term “substantially” may modify any value or relative characteristic disclosed or claimed in the present disclosure. “Substantially” may signify that the value or relative characteristic it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or 10% of the value or relative characteristic.
[0019] Reference is being made in detail to compositions, embodiments, and methods of embodiments known to the inventors. However, disclosed embodiments are merely exemplary of the present disclosure which may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, rather merely as representative bases for teaching one skilled in the art to variously employ the present disclosure.
[0020] Electrochemical cells show great potential as an alternative solution for energy production and consumption. For instance, fuel cells are being developed as electrical power sources for automobile applications, and electrolyzers are being used for hydrogen production from renewal resources (e.g. water). However, widespread adoption of the electrochemical cells requires further research into lifetime and cost reduction for components used in the electrochemical cells. These components include an electrolyte membrane and catalyst layers separated by the electrolyte membrane.
[0021] A typical single polymer electrolyte membrane (PEM) fuel cell is composed of a PEM, an anode layer, a cathode layer, and gas diffusion layers (GDLs). These components form a membrane electrode assembly (MEA), which is surrounded by two flow field plates. A catalyst material, such as platinum (Pt) catalysts, is included in the anode and cathode layers of the PEM fuel cell. At the anode layer, Pt catalysts catalyze a hydrogen oxidation reaction (HOR, H.sub.2.fwdarw.2H.sup.++2e.sup.−), where H.sub.2 is oxidized to generate electrons and protons (H.sup.+). At the cathode layer, Pt catalysts catalyze an oxygen reduction reaction (ORR, ½O.sub.2+2H.sup.++2e.sup.−.fwdarw.H.sub.2O), where O.sub.2 reacts with H.sup.+ and is reduced to form water.
[0022] Due to dynamic changes of operational conditions in the PEM fuel cell, Pt catalysts may be subject to various degradations, including dissolution, migration, and re-deposition. In addition, because the kinetics of an ORR is significantly slower than that of an HOR, a higher loading of Pt catalysts is required at the cathode layer than the anode layer. Further, the sizes of Pt catalysts may grow during a normal operation of the PEM fuel cell. The growth of the Pt catalysts may cause a loss of an electrochemical surface area (ECSA), which adversely affects the HOR and/or ORR and leads to the degradation of the PEM fuel cell.
[0023] Global H.sub.2 fuel starvation may occur, especially at the anode layer of the PEM fuel cell. The occurrence of H.sub.2 fuel starvation may substantially impact the performance of the PEM fuel cell. Specifically, due to a lack of H.sub.2 fuel, an oxygen evolution reaction (OER, 2H.sub.2O.fwdarw.O.sub.2+4H.sup.++4e), i.e., water electrolysis, may occur at 1.23 V vs. standard hydrogen electrode (SHE) at the anode layer. A carbon oxidation reaction (COR, C+2H.sub.2O.fwdarw.CO.sub.2+4 H.sup.++4e.sup.−) may also take place at 0.21 V vs. SHE at the anode layer. For a normal fuel cell operation, i.e., when there is no H.sub.2 fuel starvation, a cathode voltage at the cathode layer is normally higher than the anode voltage at the anode layer, as the HOR takes place at 0.00 V vs. SHE. A cell terminal voltage between the cathode and anode voltages is normally above 0.00 V. However, when H.sub.2 fuel starvation occurs, the OER and/or COR increases the anode voltage at the anode layer, causing the cell terminal voltage to decrease, i.e., causing cell voltage reversal. For example, the cell terminal voltage may drop below −2.00 V. In addition, the COR may lead to carbon corrosion at the anode layer. The occurrence of cell voltage reversal may also generate a significant amount of waste heat, which further damages the MEA and accelerates the degradation of the PEM fuel cell.
[0024] To alleviate or prevent cell voltage reversal due to H.sub.2 fuel starvation, metal elements such as ruthenium (Ru) or iridium (Ir), as well as their metal oxides such as RuO.sub.2 or IrO.sub.2, may be added to the anode layer of the PEM fuel cell. The incorporation of Ru and/or Ir element may help reduce carbon corrosion at the anode layer during H.sub.2 fuel starvation. For instance, a voltage of about 0.6 to 0.7 V is typically required to fully recover Pt surfaces from catalyst poisoning (i.e., to oxidize CO to CO.sub.2 gas). However, due to the presence of Ru, about 0.35 V is required to fully recover Pt—Ru surfaces from catalyst poisoning. Furthermore, some Ir-based intermetallic compounds, such as IrRu.sub.4Y.sub.0.5 or IrRu.sub.4, may also be added to the anode layer to prevent carbon corrosion and/or water hydrolysis during H.sub.2 fuel starvation. However, because these metals and metal oxides are relatively expensive, using them in the anode layer undesirably increase the total cost of the PEM fuel cell.
[0025] Therefore, there is a need for an electrochemical cell anode catalyst material that is not only relatively low-cost but comparatively effective as adding Ru and/or Ir element to the anode layer to prevent cell voltage reversal during H.sub.2 fuel starvation. Aspects of the present disclosure are directed to anode catalyst materials for electrochemical cells, for example, anode catalyst materials for fuel cells or electrolyzers. The anode catalyst material may be a Pt-based alloy. In one embodiment, the Pt-based alloy may be a binary Pt-M alloy, where M may be Ge, Se, Ag, Sb, Os, or Tl. In another embodiment, the Pt-based alloy may be a ternary Pt-M.sup.I-M.sup.II alloy, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd.
[0026]
[0027] In addition, a first side 24 of the MEA 22 is bound by an anode flow field plate 28, and the second side 26 of the MEA 22 is bounded by a cathode flow field plate 30. The anode flow field plate 28 includes an anode flow field 32 configured to distribute H.sub.2 to the MEA 22. The cathode flow field plate 30 includes a cathode flow field 34 configured to distribute O.sub.2 to the MEA 22.
[0028]
[0029] The processor 52 may be configured to read into memory and execute computer-executable instructions residing in a DFT software module 58 of the non-volatile storage 56 and embodying DFT slab model algorithms, calculations and/or methodologies of one or more embodiments. The DFT software module 58 may include operating systems and applications. The DFT software module 58 may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, Java, C, C++, C#, Objective C, Fortran, Pascal, Java Script, Python, Perl, and PL/SQL.
[0030] Upon execution by the processor 52, the computer-executable instructions of the DFT software module 58 may cause the computing platform 50 to implement one or more of the DFT algorithms and/or methodologies disclosed herein. The non-volatile storage 56 may also include DFT data 60 supporting the functions, features, calculations, and processes of the one or more embodiments described herein.
[0031] The program code embodying the algorithms and/or methodologies described herein is capable of being individually or collectively distributed as a program product in a variety of different forms. The program code may be distributed using a computer readable storage medium having computer readable program instructions thereon for causing a processor to carry out aspects of one or more embodiments. The computer readable storage medium, which is inherently non-transitory, may include volatile and non-volatile, and removable and non-removable tangible media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules, or other data. The computer readable storage media may further include RAM, ROM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other solid state memory technology, portable compact disc read-only memory (CD-ROM), or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and which can be read by a computer. Computer readable program instructions may be downloaded to a computer, another type of programmable data processing apparatus, or another device from a computer readable storage medium or to an external computer or external storage device via a network.
[0032] Computer readable program instructions stored in the computer readable medium may be used to direct a computer, other types of programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions that implement the functions, acts, and/or operations specified in the flowcharts or diagrams. In certain alternative embodiments, the functions, acts, and/or operations specified in the flowcharts and diagrams may be re-ordered, processed serially, and/or processed concurrently consistent with one or more embodiments. Moreover, any of the flowcharts and/or diagrams may include more or fewer nodes or blocks than those illustrated consistent with one or more embodiments.
[0033] Referring to
[0034] Table 1 depicts information of reactions between Pt and O.sub.2, H.sub.2O.sub.2, or OOH, respectively, under similar reaction conditions. Table 1 provides a reaction equation and a reaction enthalpy (E, eV/atom) for each reaction.
TABLE-US-00001 TABLE 1 Information of reactions between Pt and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. E Reactant Equation of the reaction (eV/atom) O.sub.2 0.3335 O.sub.2 + 0.333 Pt .fwdarw. 0.333 PtO.sub.2 −0.937 H.sub.2O.sub.2 0.4 H.sub.2O.sub.2 + 0.2 Pt .fwdarw. 0.2 PtO.sub.2 + 0.4 H.sub.2O −0.385 OOH 0.571 HO.sub.2 + 0.429 Pt .fwdarw. 0.429 PtO.sub.2 + −0.562 0.286 H.sub.2O
[0035] Table 2 depicts information of reactions between Ir and O.sub.2, H.sub.2O.sub.2, or OOH, respectively, under similar reaction conditions. Table 2 provides a reaction equation and a reaction enthalpy (E, eV/atom) for each reaction.
TABLE-US-00002 TABLE 2 Information of reactions between Ir and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. E Reactant Equation of the reaction (eV/atom) O.sub.2 0.3335 O.sub.2 + 0.333 Ir .fwdarw. 0.333 IrO.sub.2 −1.271 H.sub.2O.sub.2 0.4 H.sub.2O.sub.2 + 0.2 Ir .fwdarw. 0.4 H.sub.2O + 0.2 IrO.sub.2 −0.497 OOH 0.571 HO.sub.2 + 0.429 Ir .fwdarw. 0.286 H.sub.2O + 0.429 IrO.sub.2 −0.763
[0036] Table 3 depicts information of reactions between Ru and O.sub.2, H.sub.2O.sub.2, or OOH, respectively, under similar reaction conditions. Table 3 provides a reaction equation and a reaction enthalpy (E, eV/atom) for each reaction.
TABLE-US-00003 TABLE 3 Information of reactions between Ru and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. E Reactant Equation of the reaction (eV/atom) O.sub.2 0.3335 O.sub.2 + 0.333 Ru .fwdarw. 0.333 RuO.sub.2 −1.468 H.sub.2O.sub.2 0.4 H.sub.2O.sub.2 + 0.2 Ru .fwdarw. 0.4 H.sub.2O + 0.2 RuO.sub.2 −0.562 OOH 0.571 HO.sub.2 + 0.429 Ru .fwdarw. 0.286 H.sub.2O + −0.881 0.429 RuO.sub.2
[0037] In view of Tables 1 to 3, the reactions between Ir and O.sub.2, H.sub.2O.sub.2, or OOH appear to be more favorable than the reactions between Pt and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. Further, the reactions between Ru and O.sub.2, H.sub.2O.sub.2, or OOH appear to be more favorable than the reactions between Ir and O.sub.2, H.sub.2O.sub.2, or OOH, respectively, and thus more favorable than the reactions between Pt and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. This indicates that when using either Ir or Ru alone as an anode catalyst in the anode layer of an electrochemical cell, the anode catalyst may be less stable than using Pt alone as the anode catalyst. Using either Ir or Ru alone as the anode catalyst in the anode layer may not help prevent cell voltage reversal during H.sub.2 fuel starvation.
[0038] Table 4 depicts information of reactions between Pt.sub.0.75Ir.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH, respectively, under similar reaction conditions. Table 4 provides a reaction equation and a reaction enthalpy (E, eV/atom) for each reaction.
TABLE-US-00004 TABLE 4 Information of reactions between Pt.sub.0.75Ir.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. E Reactant Equation of the reaction (eV/atom) O.sub.2 0.3335 O.sub.2 + 0.333 Ir.sub.0.25Pt.sub.0.75 .fwdarw. 0.25 PtO.sub.2 + 0.083 IrO.sub.2 −1.020 H.sub.2O.sub.2 0.375 H.sub.2O.sub.2 + 0.25 Ir.sub.0.25Pt.sub.0.75 .fwdarw. 0.063 Pt.sub.3O.sub.4 + 0.063 IrO.sub.2 + 0.375 H.sub.2O −0.416 OOH 0.571 HO.sub.2 + 0.429 Ir.sub.0.25Pt.sub.0.75 .fwdarw. 0.321 PtO.sub.2 + 0.107 IrO.sub.2 + 0.286 H.sub.2O −0.612
[0039] Table 5 depicts information of reactions between Pt.sub.0.75Ru.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH, respectively, under similar reaction conditions. Table 5 provides a reaction equation and a reaction enthalpy (E, eV/atom) for each reaction.
TABLE-US-00005 TABLE 5 Information of reactions between Pt.sub.0.75Ru.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. E Reactant Equation of the reaction (eV/atom) O.sub.2 0.3335 O.sub.2 + 0.333 Ru.sub.0.25Pt.sub.0.75 .fwdarw. 0.25 PtO.sub.2 + 0.083 RuO.sub.2 −1.070 H.sub.2O.sub.2 0.375 H.sub.2O.sub.2 + 0.25 Ru.sub.0.25Pt.sub.0.75 .fwdarw. 0.063 Pt.sub.3O.sub.4 + 0.063 RuO.sub.2 + 0.375 H.sub.2O −0.437 OOH 0.571 HO.sub.2 + 0.429 Ru.sub.0.25Pt.sub.0.75 .fwdarw. 0.321 PtO.sub.2 + 0.107 RuO.sub.2 + 0.286 H.sub.2O −0.642
[0040] In view of Tables 2 and 4, the reactions between Pt.sub.0.75Ir.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH appears to be less favorable than the reactions between Ir and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. This suggests that adding Ir to Pt, thereby forming a Pt—Ir alloy, may help increase the stability of the anode catalyst as compared to using Ir alone as the anode catalyst in the anode layer of the electrochemical cell.
[0041] Similarly, in view of Tables 3 and 5, the reactions between Pt.sub.0.75Ru.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH appear to be less favorable than the reactions between Ru and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. Adding Ru to Pt, thereby forming a Pt—Ru alloy, may also help increase the stability of the anode catalyst as compared to using Ru alone as the anode catalyst in the anode layer of the PEM fuel cell.
[0042] Further, when comparing the chemical reactivities of Pt.sub.0.75Ir.sub.0.25 and Pt.sub.0.75Ru.sub.0.25 in Tables 4 and 5, Pt.sub.0.75Ir.sub.0.25 appears to be less chemically reactive against O.sub.2, H.sub.2O.sub.2, or OOH than Pt.sub.0.75Ru.sub.0.25. This further indicates that Pt.sub.0.75Ir.sub.0.25 may be more suitable than Pt.sub.0.75Ru.sub.0.25 to be used as an electrochemical cell anode catalyst material to prevent cell voltage reversal during H.sub.2 fuel starvation.
[0043] Apart from Pt—Ir and Pt—Ru alloys, other metal elements M, such as palladium (Pd) or cerium (Ce), may be mixed with Pt to form Pt-M alloys. Table 6 depicts information of reactions between Pt.sub.0.75Pd.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH, respectively, under similar reaction conditions. Table 6 provides a reaction equation and a reaction enthalpy (E, eV/atom) for each reaction.
TABLE-US-00006 TABLE 6 Information of reactions between Pt.sub.0.75Pd.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. E Reactant Equation of the reaction (eV/atom) O.sub.2 0.318 O.sub.2 + 0.364 Pd.sub.0.25Pt.sub.0.75 .fwdarw. 0.273 PtO.sub.2 + 0.091 PdO −0.905 H.sub.2O.sub.2 0.389 H.sub.2O.sub.2 + 0.222 Pd.sub.0.25Pt.sub.0.75 .fwdarw. 0.167 PtO.sub.2 + 0.056 PdO + 0.389 H.sub.2O −0.383 OOH 0.538 HO.sub.2 + 0.462 Pd.sub.0.25Pt.sub.0.75 .fwdarw. 0.346 PtO.sub.2 + 0.115 PdO + 0.269 H.sub.2O −0.553
[0044] Table 7 depicts information of reactions between Pt.sub.0.75Ce.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH, respectively, under similar reaction conditions. Table 7 provides a reaction equation and a reaction enthalpy (E, eV/atom) for each reaction.
TABLE-US-00007 TABLE 7 Information of reactions between Pt.sub.0.75Ce.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. E Reactant Equation of the reaction (eV/atom) O.sub.2 0.3 O.sub.2 + 0.4 Ce.sub.0.25Pt.sub.0.75 .fwdarw. 0.1 Pt.sub.3O.sub.4 + 0.1 CeO.sub.2 −1.381 H.sub.2O.sub.2 0.5 Ce.sub.0.25Pt.sub.0.75 + 0.25 H.sub.2O.sub.2 .fwdarw. 0.25 H.sub.2O + 0.125 CeO.sub.2 + 0.375 Pt −0.718 OOH 0.75 Ce.sub.0.25Pt.sub.0.75 + 0.25 HO.sub.2 .fwdarw. 0.125 H.sub.2O + 0.188 CeO.sub.2 + 0.562 Pt −0.995
[0045] In view of Tables 6 and 7, the reactions between Pt.sub.0.75Pd.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH appear to be less favorable than the reactions between Pt.sub.0.75Ce.sub.0.25 and O.sub.2, H.sub.2O.sub.2, or OOH, respectively. This indicates that Pt.sub.0.75Pd.sub.0.25 may be more stable than Pt.sub.0.75Ce.sub.0.25 in an oxidizing environment. In other words, adding Pd to Pt, thereby forming a Pt—Pd alloy, may help increase the stability of the anode catalyst as compared to adding the same amount of Ce to Pt to form a Pt—Ce alloy.
[0046] Further, when comparing the chemical reactivities of Pt.sub.0.75Pd.sub.0.25 and Pt.sub.0.75Ir.sub.0.25 in Tables 4 and 6, Pt.sub.0.75Pd.sub.0.25 appears to be less chemically reactive against O.sub.2, H.sub.2O.sub.2, or OOH than Pt.sub.0.75Ir.sub.0.25. This further indicates that Pt.sub.0.75Pd.sub.0.25 may be more suitable than Pt.sub.0.75Ir.sub.0.25 to be used as a fuel cell anode catalyst material to prevent cell voltage reversal during H.sub.2 fuel starvation.
[0047] To further examine the chemical reactivity of a Pt-M alloy against O.sub.2, H.sub.2O.sub.2, or OOH, the data-driven materials screening method may be utilized to identify other Pt-M alloys that are suitable to be used as electrochemical cell anode catalyst materials to prevent cell voltage reversal during H.sub.2 fuel starvation. In addition to Ru, Ir, Pd, and Ce, M may also be, for example, titanium (Ti), germanium (Ge), selenium (Se), zirconium (Zr), niobium (Nb), molybdenum (Mo), rhodium (Rh), silver (Ag), tin (Sn), antimony (Sb), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), gold (Au), thallium (Tl), or bismuth (Bi).
[0048] Table 8 depicts information of thermodynamic decomposition products of a Pt-M alloy, where M may be Ti, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, Ce, Hf, Ta, W, Re, Os, Ir, Au, Tl, or Bi. Each Pt-M alloy in Table 8 shows a ratio of Pt to M as 2, i.e., Pt.sub.0.67M.sub.0.33. Pt.sub.0.67M.sub.0.33 may also be represented as Pt.sub.xM.sub.y, where x=2y, x>0, and M may be Ti, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, Ce, Hf, Ta, W, Re, Os, Ir, Au, Tl, or Bi. Noted that Pt-M alloys having ratios of Pt to M other than 2 may similarly be evaluated using the method described herein. For instance, in some other embodiments, the data-driven materials screening method may be utilized to evaluate Pt-M alloys, such as Pt.sub.0.95M.sub.0.05 or Pt.sub.0.5M.sub.0.5, where M may be Ti, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, Ce, Hf, Ta, W, Re, Os, Ir, Au, Tl, or Bi, to identify those suitable to be used as electrochemical cell anode catalyst materials to prevent cell voltage reversal during H.sub.2 fuel starvation.
[0049] Table 8 provides a thermodynamic decomposition reaction of each Pt-M alloy. The thermodynamic decomposition products of each reaction are obtained using “interface reactions” module kit available on materialsproject.org. Among the thermodynamic decomposition products of each reaction, some are cubic phases, and some are non-cubic phases. A percentage of the non-cubic phases of the thermodynamic decomposition products for each reaction may be calculated. For example, the thermodynamic decomposition products of Pt.sub.0.67Ru.sub.0.33 may be 0.67 Pt and 0.33 Ru, where Pt belongs to a cubic crystal system (Fm-3m), and Ru belongs to a hexagonal crystal system (P6.sub.3/mmc). Therefore, the percentage of the non-cubic phases of the thermodynamic decomposition products for Pt.sub.0.67Ru.sub.0.33 is calculated as 0.33/(0.67+0.33), which is about 0.33. Table 8 further provides a penalty point (PP1) to indicate the percentage of the non-cubic phases of the thermodynamic decomposition products for each reaction. For easy comparison, a PP1 of 0 is assigned to the scenario where 100% of the thermodynamic decomposition products are cubic phases. As such, the PP1 for Pt.sub.0.67Ru.sub.0.33 is 0.330.
TABLE-US-00008 TABLE 8 Information of thermodynamic decomposition products of a Pt-M alloy, where M may be Ti, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, Ce, Hf, Ta, W, Re, Os, Ir, Au, Tl, or Bi. M Thermodynamic decomposition reaction PP1 Ti Ti.sub.0.33Pt.sub.0.67 .fwdarw. 0.08 Ti.sub.3Pt.sub.5 + 0.09 TiPt.sub.3 1.000 Ge Ge.sub.0.33Pt.sub.0.67 .fwdarw. 0.107 Ge.sub.2Pt.sub.3 + 0.117 GePt.sub.3 1.000 Se Pt.sub.0.67Se.sub.0.33 .fwdarw. 0.083 Pt.sub.5Se.sub.4 + 0.258 Pt 0.243 Zr Zr.sub.0.33Pt.sub.0.67 .fwdarw. 0.029 Zr.sub.7Pt.sub.10 + 0.126 ZrPt.sub.3 1.000 Nb Nb.sub.0.33Pt.sub.0.67 .fwdarw. 0.32 NbPt.sub.2 + 0.01 NbPt.sub.3 1.000 Mo Mo.sub.0.33Pt.sub.0.67 .fwdarw. 0.33 MoPt.sub.2 + 0.01 Pt 0.971 Ru Ru.sub.0.33Pt.sub.0.67 .fwdarw. 0.33 Ru + 0.67 Pt 0.330 (reference) Rh Pt.sub.0.67Rh.sub.0.33 .fwdarw. 0.21 Pt.sub.3Rh + 0.04 PtRh.sub.3 1.000 Pd Pd.sub.0.33Pt.sub.0.67 .fwdarw. 0.33 PdPt + 0.34 Pt 0.500 Ag Ag.sub.0.33Pt.sub.0.67 .fwdarw. 0.113 AgPt.sub.4 + 0.217 AgPt 1.000 Sn Sn.sub.0.33Pt.sub.0.67 .fwdarw. 0.17 SnPt.sub.3 + 0.16 SnPt 0.500 Sb Sb.sub.0.33Pt.sub.0.67 .fwdarw. 0.165 Sb.sub.2Pt.sub.3 + 0.175 Pt 0.485 Ce Ce.sub.0.33Pt.sub.0.67 .fwdarw. 0.064 Ce.sub.3Pt.sub.4 + 0.138 CePt.sub.3 0.317 Hf Hf.sub.0.33Pt.sub.0.67 .fwdarw. 0.17 HfPt.sub.3 + 0.16 HfPt 1.000 Ta Ta.sub.0.33Pt.sub.0.67 .fwdarw. 0.01 TaPt.sub.3 + 0.32 TaPt.sub.2 1.000 W Pt.sub.0.67W.sub.0.33 .fwdarw. 0.33 Pt.sub.2W + 0.01 Pt 0.971 Re Re.sub.0.33Pt.sub.0.67 .fwdarw. 0.11 Re.sub.3Pt + 0.56 Pt 0.164 Os Os.sub.0.33Pt.sub.0.67 .fwdarw. 0.33 Os + 0.67 Pt 0.333 Ir Ir.sub.0.33Pt.sub.0.67 .fwdarw. 0.33 Ir + 0.67 Pt 0.333 Au Pt.sub.0.67Au.sub.0.33 .fwdarw. 0.67 Pt + 0.33 Au 0.333 Tl Tl.sub.0.33Pt.sub.0.67 .fwdarw. 0.165 Tl.sub.2Pt.sub.3 + 0.175 Pt 0.485 Bi Bi.sub.0.33Pt.sub.0.67 .fwdarw. 0.34 Pt + 0.33 BiPt 0.500
[0050] To determine the percentage of cubic or non-cubic phases in the thermodynamic decomposition products of an alloy, such as a Pt-based alloy, X-ray diffraction (XRD) techniques may be employed. Particularly, an XRD pattern of a cubic phase may show strong signature peaks at (111), (110), and/or (100), representing face-centered cubic (fcc) characters. On the other hand, an XRD pattern of a non-cubic phase may show small impurity peaks, which can be differentiated from the signature peaks for cubic phases. In addition, the XRD techniques may be used to determine an average crystallite size of a Pt-based alloy nanoparticle. A size distribution of the Pt-based alloy nanoparticles may be determined using high-resolution transmission electron microscope (HR-TEM) imaging techniques. An average size of a Pt-based alloy nanoparticle may be in a range of 1 and 20 nm, or alternatively, between 3 and 10 nm.
[0051] In addition to the composition of the Pt-based alloy, the properties of the Pt-based alloy may also vary depending on its microstructure, morphology, and/or crystallinity. A lattice mismatch between the thermodynamic decomposition products of the Pt-based alloy may impact a local structure and/or electronic structure of the alloy. When the Pt-based alloy nanoparticles are de-alloyed near a surface, a lattice constant in a bulk region may decrease, thereby leading to a compressive strain at an outer Pt surface. In general, such an effect may increase the catalyst activity. Further, introducing tensile strain and/or increasing lattice constants may enhance the durability of the Pt-based alloy.
[0052]
0.509OOH+0.491Ru.sub.0.33Pt.sub.0.67.fwdarw.0.11Pt.sub.3O.sub.4+0.162RuO.sub.2+0.254H.sub.2O (1)
According to Reaction (1), after reacting with 0.509 OOH, Pt.sub.0.67Ru.sub.0.33 is turned into 0.11 Pt.sub.3O.sub.4 and 0.162 RuO.sub.2.
[0053] Using the same evaluation method as described in
[0054] Table 9 also provides a reaction enthalpy (E, eV/atom) of the most stable decomposition reaction between each Pt.sub.0.67M.sub.0.33 and OOH. Table 9 further provides a penalty point (e.g. PP3) regarding the reaction enthalpy, where PP3 of 1.000 is assigned to the reference reaction between OOH and Pt.sub.0.67Ru.sub.0.33 (i.e. −0.672 eV/atom). PP3 is calculated by dividing the reaction enthalpy between OOH and each Pt.sub.0.67M.sub.0.33 of each reaction by that between OOH and Pt.sub.0.67Ru.sub.0.33. For example, since the reaction enthalpy of the reaction between OOH and Pt.sub.0.67Ti.sub.0.33 is −1.107 eV/atom, PP3 thus equals −1.107/−0.672, which is about 1.647.
[0055] If both the molar fraction between OOH and Pt.sub.0.67M.sub.0.33, and the reaction enthalpy of the reaction between OOH and Pt.sub.0.67M.sub.0.33 are greater than those for Pt.sub.0.67Ru.sub.0.33, it may indicate that the Pt.sub.0.67M.sub.0.33 is more stable than Pt.sub.0.67Ru.sub.0.33, and thus, more suitable to be used as an electrochemical cell anode catalyst material to prevent cell voltage reversal during H.sub.2 fuel starvation. For example, because the molar fraction between OOH and Pt.sub.0.67Pd.sub.0.33 (i.e. 1.114) and the reaction enthalpy of the most stable decomposition reaction between OOH and Pt.sub.0.67Pd.sub.0.33 (i.e., −0.548 eV/atom) are both greater than those for Pt.sub.0.67Ru.sub.0.33, Pt.sub.0.67Pd.sub.0.33 may therefore be more stable than Pt.sub.0.67Ru.sub.0.33, consistent with the observation in Tables 5 and 6. For another example, because the molar fraction between OOH and Pt.sub.0.67Ce.sub.0.33 (i.e. 0.441) and the reaction enthalpy of the most stable decomposition reaction between OOH and Pt.sub.0.67Ce.sub.0.33 (i.e., −1.241 eV/atom) are both less than those for Pt.sub.0.67Ru.sub.0.33, Pt.sub.0.67Ce.sub.0.33 may therefore be less stable than Pt.sub.0.67Ru.sub.0.33, consistent with the observation in Tables 6 and 7.
TABLE-US-00009 TABLE 9 Information of the most stable decomposition reaction between each Pt.sub.0.67M.sub.0.33 and OOH, where M may be Ti, Ge, Se, Zr, Nb, Mo, Rh, Pd, Ag, Sn, Sb, Ce, Hf, Ta, W, Re, Os, Ir, Au, Tl, or Bi. Equation of the most stable decomposition reaction Molar E M between Pt.sub.0.67M.sub.0.33 and OOH fraction PP2 (eV/atom) PP3 Ru 0.509 HO.sub.2 + 0.491 Ru.sub.0.33Pt.sub.0.67 .fwdarw. 0.11 Pt.sub.3O.sub.4 + 0.162 1.040 1.000 −0.672 1.000 (reference) RuO2 + 0.254 H.sub.2O Ti 0.306 HO.sub.2 + 0.694 Ti.sub.0.33Pt.sub.0.67 .fwdarw. 0.153 H.sub.2O + 0.229 0.441 2.351 −1.107 1.647 TiO.sub.2 + 0.465 Pt Ge 0.509 HO.sub.2 + 0.491 Ge.sub.0.33Pt.sub.0.67 .fwdarw. 0.11 Pt.sub.3O.sub.4 + 0.162 1.037 1.000 −0.730 1.086 GeO.sub.2 + 0.254 H.sub.2O Se 0.429 Pt.sub.0.67Se.sub.0.33 + 0.571 HO.sub.2 .fwdarw. 0.287 PtO.sub.2 + 0.286 1.331 0.779 −0.563 0.838 H.sub.2O + 0.141 SeO.sub.2 Zr 0.306 HO.sub.2 + 0.694 Zr.sub.0.33Pt.sub.0.67 .fwdarw. 0.153 H.sub.2O + 0.229 0.441 2.351 −1.180 1.756 ZrO.sub.2 + 0.465 Pt Nb 0.355 HO.sub.2 + 0.645 Nb.sub.0.33Pt.sub.0.67 .fwdarw. 0.106 Nb.sub.2O.sub.5 + 0.177 0.550 1.884 −1.069 1.591 H.sub.2O + 0.432 Pt Mo 0.602 Mo.sub.0.33Pt.sub.0.67 + 0.398 HO.sub.2 .fwdarw. 0.199 MoO.sub.3 + 0.199 0.661 1.568 −0.776 1.155 H.sub.2O + 0.404 Pt Rh 0.571 HO.sub.2 + 0.429 Pt.sub.0.67Rh.sub.0.33 .fwdarw. 0.287 PtO.sub.2 + 0.286 1.331 0.779 −0.619 0.921 H.sub.2O + 0.141 RhO.sub.2 Pd 0.527 HO.sub.2 + 0.473 Pd.sub.0.33Pt.sub.0.67 .fwdarw. 0.317 PtO.sub.2 + 0.156 1.114 0.930 −0.548 0.815 PdO + 0.263 H.sub.2O Ag 0.472 HO.sub.2 + 0.528 Ag.sub.0.33Pt.sub.0.67 .fwdarw. 0.354 PtO.sub.2 + 0.236 0.940 1.103 −0.502 0.747 H.sub.2O + 0.174 Ag Sn 0.491 Sn.sub.0.33Pt.sub.0.67 + 0.509 HO.sub.2 .fwdarw. 0.11 Pt.sub.3O.sub.4 + 0.162 1.037 1.000 −0.722 1.074 SnO.sub.2 + 0.254 H.sub.2O Sb 0.509 HO.sub.2 + 0.491 Sb.sub.0.33Pt.sub.0.67 .fwdarw. 0.11 Pt.sub.3O.sub.4 + 0.162 1.037 1.000 −0.691 1.028 SbO.sub.2 + 0.254 H.sub.2O Ce 0.694 Ce.sub.0.33Pt.sub.0.67 + 0.306 HO.sub.2 .fwdarw. 0.153 H.sub.2O + 0.229 0.441 2.351 −1.241 1.847 CeO.sub.2 + 0.465 Pt Hf 0.306 HO.sub.2 + 0.694 Hf.sub.0.33Pt.sub.0.67 .fwdarw. 0.153 H.sub.2O + 0.229 0.441 2.351 −1.242 1.848 HfO.sub.2 + 0.465 Pt Ta 0.355 HO.sub.2 + 0.645 Ta.sub.0.33Pt.sub.0.67 .fwdarw. 0.177 H.sub.2O + 0.106 0.550 1.884 −1.180 1.756 Ta.sub.2O.sub.5 + 0.432 Pt W 0.602 Pt.sub.0.67W.sub.0.33 + 0.398 HO.sub.2 .fwdarw. 0.199 WO.sub.3 + 0.199 0.661 1.568 −0.852 1.268 H.sub.2O + 0.404 Pt Re 0.398 HO.sub.2 + 0.602 Re.sub.0.33Pt.sub.0.67 .fwdarw. 0.199 H.sub.2O + 0.199 0.661 1.568 −0.916 1.363 ReO.sub.3 + 0.404 Pt Os 0.596 HO.sub.2 + 0.404 Os.sub.0.33Pt.sub.0.67 .fwdarw. 0.09 Pt.sub.3O.sub.4 + 0.133 1.475 0.703 −0.709 1.055 OsO.sub.4 + 0.298 H.sub.2O Ir 0.571 HO.sub.2 + 0.429 Ir.sub.0.33Pt.sub.0.67 .fwdarw. 0.287 PtO.sub.2 + 0.141 1.331 0.779 −0.628 0.935 IrO.sub.2 + 0.286 H.sub.2O Au 0.472 HO.sub.2 + 0.528 Pt.sub.0.67Au.sub.0.33 .fwdarw. 0.354 PtO.sub.2 + 0.236 0.894 1.160 −0.512 0.762 H.sub.2O + 0.174 Au Tl 0.55 HO.sub.2 + 0.45 Tl.sub.0.33Pt.sub.0.67 .fwdarw. 0.153 PtO.sub.2 + 0.074 1.222 0.848 −0.637 0.948 Tl.sub.2Pt.sub.2O.sub.7 + 0.275 H.sub.2O Bi 0.517 HO.sub.2 + 0.483 Bi.sub.0.33Pt.sub.0.67 .fwdarw. 0.08 Bi.sub.2Pt.sub.2O.sub.7 + 0.055 1.070 0.968 −0.692 1.030 Pt.sub.3O.sub.4 + 0.259 H.sub.2O
[0056] Table 10 depicts information of the most stable decomposition reaction between each Pt.sub.0.67M.sub.0.33 and H.sub.2O.sub.2. Particularly, Table 10 provides a reaction equation of the most stable decomposition reaction between each Pt.sub.0.67M.sub.0.33 and H.sub.2O.sub.2. Table 10 also provides a molar fraction between H.sub.2O.sub.2 and each Pt.sub.0.67M.sub.0.33 for each reaction. Information of the most stable decomposition reaction between Pt.sub.0.67Ru.sub.0.33 and H.sub.2O.sub.2 is used as a reference for comparison. Table 10 further provides a penalty point (e.g. PP4) regarding the molar fraction, where PP4 of 1.000 is assigned to the reference reaction between H.sub.2O.sub.2 and Pt.sub.0.67Ru.sub.0.33 (i.e. the molar fraction is 1.320). PP4 is calculated by dividing the molar fraction between H.sub.2O.sub.2 and Pt.sub.0.67Ru.sub.0.33 by the molar fraction between H.sub.2O.sub.2 and each Pt.sub.0.67M.sub.0.33 of each reaction. For example, since the molar fraction between H.sub.2O.sub.2 and Pt.sub.0.67Ti.sub.0.33 is 1.320, PP4 thus equals 1.320/1.320, which is about 1.000.
[0057] Table 10 also provides a reaction enthalpy (E, eV/atom) of the most stable decomposition reaction between each Pt.sub.0.67M.sub.0.33 and H.sub.2O.sub.2. Table 10 further provides a penalty point (e.g. PP5) regarding the reaction enthalpy, where PP5 of 1.000 is assigned to the reference reaction between H.sub.2O.sub.2 and Pt.sub.0.67Ru.sub.0.33 (i.e. −0.459 eV/atom). PP5 is calculated by dividing the reaction enthalpy between H.sub.2O.sub.2 and each Pt.sub.0.67M.sub.0.33 of each reaction by that between H.sub.2O.sub.2 and Pt.sub.0.67Ru.sub.0.33. For example, since the reaction enthalpy of the reaction between H.sub.2O.sub.2 and Pt.sub.0.67Ti.sub.0.33 is −0.765 eV/atom, PP5 thus equals −0.765/−0.459, which is about 1.667.
[0058] If both the molar fraction between H.sub.2O.sub.2 and Pt.sub.0.67M.sub.0.33, and the reaction enthalpy of the reaction between H.sub.2O.sub.2 and Pt.sub.0.67M.sub.0.33 are greater than those for Pt.sub.0.67Ru.sub.0.33, it may indicate that the Pt.sub.0.67M.sub.0.33 is more stable than Pt.sub.0.67Ru.sub.0.33. Otherwise, Pt.sub.0.67M.sub.0.33 may be less stable than Pt.sub.0.67Ru.sub.0.33.
TABLE-US-00010 TABLE 10 Information of the most stable decomposition reaction between Pt.sub.0.67M.sub.0.33 and H.sub.2O.sub.2, where M may be Ti, Ge, Se, Zr, Nb, Mo, Rh, Pd, Ag, Sn, Sb, Ce, Hf, Ta, W, Re, Os, Ir, Au, Tl, or Bi. Equation of the most stable decomposition reaction Molar E M between Pt.sub.0.67M.sub.0.33 and H.sub.2O.sub.2 fraction PP4 (eV/atom) PP5 Ru 0.2845 H.sub.2O.sub.2 + 0.431 Ru.sub.0.33Pt.sub.0.67 .fwdarw. 0.142 RuO.sub.2 + 1.320 1.000 −0.459 1.000 (reference) 0.284 H.sub.2O + 0.289 Pt Ti 0.2845 H.sub.2O.sub.2 + 0.431 Ti.sub.0.33Pt.sub.0.67 .fwdarw. 0.284 H.sub.2O + 1.320 1.000 −0.765 1.667 0.142 TiO.sub.2 + 0.289 Pt Ge 0.2845 H.sub.2O.sub.2 + 0.431 Ge.sub.0.33Pt.sub.0.67 .fwdarw. 0.142 GeO.sub.2 + 1.320 1.000 −0.525 1.144 0.284 H.sub.2O + 0.289 Pt Se 0.2 Pt.sub.0.67Se.sub.0.33 + 0.4 H.sub.2O.sub.2 .fwdarw. 0.134 PtO.sub.2 + 0.4 H.sub.2O + 4.000 0.330 −0.386 0.841 0.066 SeO.sub.2 Zr 0.2845 H.sub.2O.sub.2 + 0.431 Zr.sub.0.33Pt.sub.0.67 .fwdarw. 0.284 H.sub.2O + 1.320 1.000 −0.812 1.769 0.142 ZrO.sub.2 + 0.289 Pt Nb 0.3115 H.sub.2O.sub.2 + 0.377 Nb.sub.0.33Pt.sub.0.67 .fwdarw. 0.062 Nb.sub.2O.sub.5 + 0.826 1.598 −0.722 1.573 0.311 H.sub.2O + 0.253 Pt Mo 0.431 Mo.sub.0.33Pt.sub.0.67 + 0.2845 H.sub.2O.sub.2 .fwdarw. 0.284 H.sub.2O + 1.320 1.000 −0.544 1.185 0.142 MoO.sub.2 + 0.289 Pt Rh 0.378 H.sub.2O.sub.2 + 0.244 Pt.sub.0.67Rh.sub.0.33 .fwdarw. 0.054 Pt.sub.3O.sub.4 + 3.098 0.426 −0.420 0.915 0.378 H.sub.2O + 0.08 RhO.sub.2 Pd 0.385 H.sub.2O.sub.2 + 0.23 Pd.sub.0.33Pt.sub.0.67 .fwdarw. 0.154 PtO.sub.2 + 0.076 3.348 0.394 −0.381 0.830 PdO + 0.385 H.sub.2O Ag 0.364 H.sub.2O.sub.2 + 0.272 Ag.sub.0.33Pt.sub.0.67 .fwdarw. 0.182 PtO.sub.2 + 2.676 0.493 −0.360 0.784 0.364 H.sub.2O + 0.09 Ag Sn 0.431 Sn.sub.0.33Pt.sub.0.67 + 0.2845 H.sub.2O.sub.2 .fwdarw. 0.142 SnO.sub.2 + 1.320 1.000 −0.515 1.122 0.284 H.sub.2O + 0.289 Pt Sb 0.2845 H.sub.2O.sub.2 + 0.431 Sb.sub.0.33Pt.sub.0.67 .fwdarw. 0.142 SbO.sub.2 + 1.320 1.000 −0.480 1.046 0.284 H.sub.2O + 0.289 Pt Ce 0.431 Ce.sub.0.33Pt.sub.0.67 + 0.2845 H.sub.2O.sub.2 .fwdarw. 0.284 H.sub.2O + 1.320 1.000 −0.851 1.854 0.142 CeO.sub.2 + 0.289 Pt Hf 0.2845 H.sub.2O.sub.2 + 0.431 Hf.sub.0.33Pt.sub.0.67 .fwdarw. 0.284 H.sub.2O + 1.320 1.000 −0.851 1.854 0.142 HfO.sub.2 + 0.289 Pt Ta 0.3115 H.sub.2O.sub.2 + 0.377 Ta.sub.0.33Pt.sub.0.67 .fwdarw. 0.311 H.sub.2O + 1.653 0.799 −0.790 1.721 0.062 Ta.sub.2O.sub.5 + 0.253 Pt W 0.336 Pt.sub.0.67W.sub.0.33 + 0.332 H.sub.2O.sub.2 .fwdarw. 0.111 WO.sub.3 + 0.332 1.976 0.668 −0.577 1.257 H.sub.2O + 0.225 Pt Re 0.332 H.sub.2O.sub.2 + 0.336 Re.sub.0.33Pt.sub.0.67 .fwdarw. 0.332 H.sub.2O + 0.111 1.976 0.668 −0.616 1.342 ReO.sub.3 + 0.225 Pt Os 0.3625 H.sub.2O.sub.2 + 0.275 Os.sub.0.33Pt.sub.0.67 .fwdarw. 0.091 OsO.sub.4 + 2.636 0.501 −0.474 1.033 0.363 H.sub.2O + 0.184 Pt Ir 0.378 H.sub.2O.sub.2 + 0.244 Ir.sub.0.33Pt.sub.0.67 .fwdarw. 0.054 Pt.sub.3O.sub.4 + 0.08 3.098 0.426 −0.426 0.928 IrO2 + 0.378 H.sub.2O Au 0.364 H.sub.2O.sub.2 + 0.272 Pt.sub.0.67Au.sub.0.33 .fwdarw. 0.182 PtO.sub.2 + 2.676 0.493 −0.365 0.795 0.364 H.sub.2O + 0.09 Au Tl 0.3815 H.sub.2O.sub.2 + 0.237 Tl.sub.0.33Pt.sub.0.67 .fwdarw. 0.027 Pt.sub.3O.sub.4 + 3.219 0.410 −0.432 0.941 0.039 Tl2Pt2O7 + 0.381 H.sub.2O Bi 0.349 H.sub.2O.sub.2 + 0.302 Bi.sub.0.33Pt.sub.0.67 .fwdarw. 0.05 Bi.sub.2Pt.sub.2O.sub.7 + 2.311 0.571 −0.468 1.020 0.349 H.sub.2O + 0.103 Pt
[0059] Table 11 depicts information of the most stable decomposition reaction between each Pt.sub.0.67M.sub.0.33 and O.sub.2. Table 11 provides a reaction equation of the most stable decomposition reaction between each Pt.sub.0.67M.sub.0.33 and O.sub.2. Table 11 also provides a molar fraction between O.sub.2 and each Pt.sub.0.67M.sub.0.33 for each reaction. Information of the most stable decomposition reaction between Pt.sub.0.67Ru.sub.0.33 and O.sub.2 is used as a reference for comparison. Table 11 further provides a penalty point (e.g. PP6) regarding the molar fraction, where PP6 of 1.000 is assigned to the reference reaction between O.sub.2 and Pt.sub.0.67Ru.sub.0.33 (i.e. the molar fraction is 1.000). PP6 is calculated by dividing the molar fraction between O.sub.2 and Pt.sub.0.67Ru.sub.0.33 by the molar fraction between O.sub.2 and each Pt.sub.0.67M.sub.0.33 of each reaction. For example, since the molar fraction between O.sub.2 and Pt.sub.0.67Ti.sub.0.33 is 0.331, PP6 thus equals 1.000/0.331, which is about 3.030.
[0060] Table 11 also provides a reaction enthalpy (E, eV/atom) of the most stable decomposition reaction between each Pt.sub.0.67M.sub.0.33 and O.sub.2. Table 11 further provides a penalty point (e.g. PP7) regarding the reaction enthalpy, where PP7 of 1.000 is assigned to the reference reaction between O.sub.2 and Pt.sub.0.67Ru.sub.0.33 (i.e. −1.112 eV/atom). PP7 is calculated by dividing the reaction enthalpy between O.sub.2 and each Pt.sub.0.67M.sub.0.33 of each reaction by that between O.sub.2 and Pt.sub.0.67Ru.sub.0.33. For example, since the reaction enthalpy of the reaction between O.sub.2 and Pt.sub.0.67Ti.sub.0.33 is −1.584 eV/atom, PP7 thus equals −1.584/−1.112, which is about 1.392.
[0061] If both the molar fraction between O.sub.2 and Pt.sub.0.67M.sub.0.33, and the reaction enthalpy of the reaction between O.sub.2 and Pt.sub.0.67M.sub.0.33 are greater than those for Pt.sub.0.67Ru.sub.0.33, it may indicate that the Pt.sub.0.67M.sub.0.33 may be more stable than Pt.sub.0.67Ru.sub.0.33. Otherwise, Pt.sub.0.67M.sub.0.33 may be less stable than Pt.sub.0.67Ru.sub.0.33.
TABLE-US-00011 TABLE 11 Information of the most stable decomposition reaction between Pt.sub.0.67M.sub.0.33 and O.sub.2, where M may be Ti, Ge, Se, Zr, Nb, Mo, Rh, Pd, Ag, Sn, Sb, Ce, Hf, Ta, W, Re, Os, Ir, Au, Tl, or Bi. Equation of the most stable decomposition reaction Molar E M between Pt.sub.0.67M.sub.0.33 and O.sub.2 fraction PP6 (eV/atom) PP7 Ru 0.3335 O.sub.2 + 0.333 Ru.sub.0.33Pt.sub.0.67 .fwdarw. 0.223 PtO.sub.2 + 0.11 RuO.sub.2 1.000 1.000 −1.112 1.000 (reference) Ti 0.199 O.sub.2 + 0.602 Ti.sub.0.33Pt.sub.0.67 .fwdarw. 0.199 TiO.sub.2 + 0.404 Pt 0.331 3.030 −1.548 1.392 Ge 0.3335 O.sub.2 + 0.333 Ge.sub.0.33Pt.sub.0.67 .fwdarw. 0.223 PtO.sub.2 + 0.11 GeO.sub.2 1.000 1.002 −1.192 1.072 Se 0.3335 O.sub.2 + 0.333 Pt.sub.0.67Se.sub.0.33 .fwdarw. 0.223 PtO.sub.2 + 0.11 SeO.sub.2 1.000 1.002 −0.938 0.844 Zr 0.199 O.sub.2 + 0.602 Zr.sub.0.33Pt.sub.0.67 .fwdarw. 0.199 ZrO.sub.2 + 0.404 Pt 0.331 3.030 −1.649 1.483 Nb 0.226 O.sub.2 + 0.548 Nb.sub.0.33Pt.sub.0.67 .fwdarw. 0.09 Nb.sub.2O.sub.5 + 0.367 Pt 0.412 2.428 −1.552 1.396 Mo 0.35 O.sub.2 + 0.3 Mo.sub.0.33Pt.sub.0.67 .fwdarw. 0.099 MoO.sub.3 + 0.201 PtO.sub.2 1.167 0.858 −0.776 0.698 Rh 0.3335 O.sub.2 + 0.333 Pt.sub.0.67Rh.sub.0.33 .fwdarw. 0.223 PtO.sub.2 + 0.11 RhO.sub.2 1.000 1.002 −1.032 0.928 Pd 0.3125 O.sub.2 + 0.375 Pd.sub.0.33Pt.sub.0.67 .fwdarw. 0.251 PtO.sub.2 + 0.124 PdO 0.833 1.202 −0.891 0.801 Ag 0.3125 O.sub.2 + 0.375 Ag.sub.0.33Pt.sub.0.67 .fwdarw. 0.251 PtO.sub.2 + 0.124 AgO 0.833 1.202 −0.804 0.723 Sn 0.3335 O.sub.2 + 0.333 Sn.sub.0.33Pt.sub.0.67 .fwdarw. 0.223 PtO.sub.2 + 0.11 SnO.sub.2 1.000 1.002 −1.180 1.061 Sb 0.342 O.sub.2 + 0.316 Sb.sub.0.33Pt.sub.0.67 .fwdarw. 0.052 Sb.sub.2O.sub.5 + 0.212 PtO.sub.2 1.082 0.925 −1.143 1.028 Ce 0.199 O.sub.2 + 0.602 Ce.sub.0.33Pt.sub.0.67 .fwdarw. 0.199 CeO.sub.2 + 0.404 Pt 0.331 3.030 −1.735 1.560 Hf 0.199 O.sub.2 + 0.602 Hf.sub.0.33Pt.sub.0.67 .fwdarw. 0.404 Pt + 0.199 HfO.sub.2 0.331 3.030 −1.736 1.561 Ta 0.226 O.sub.2 + 0.548 Ta.sub.0.33Pt.sub.0.67 .fwdarw. 0.09 Ta.sub.2O.sub.5 + 0.367 Pt 0.412 2.428 −1.713 1.540 W 0.3265 O.sub.2 + 0.347 Pt.sub.0.67W.sub.0.33 .fwdarw. 0.077 Pt.sub.3O.sub.4 + 0.114 WO.sub.3 0.941 1.064 −1.333 1.199 Re 0.3265 O.sub.2 + 0.347 Re.sub.0.33Pt.sub.0.67 .fwdarw. 0.077 Pt.sub.3O.sub.4 + 0.114 ReO.sub.3 0.941 1.064 −1.400 1.259 Os 0.3635 O.sub.2 + 0.273 Os.sub.0.33Pt.sub.0.67 .fwdarw. 0.09 OsO.sub.4 + 0.183 PtO.sub.2 1.332 0.752 −1.209 1.087 Ir 0.3335 O.sub.2 + 0.333 Ir.sub.0.33Pt.sub.0.67 .fwdarw. 0.223 PtO.sub.2 + 0.11 IrO.sub.2 1.001 1.000 −1.047 0.942 Au 0.2865 O.sub.2 + 0.427 Pt.sub.0.67Au.sub.0.33 .fwdarw. 0.286 PtO.sub.2 + 0.141 Au 0.671 1.493 −0.805 0.724 Tl 0.3235 O.sub.2 + 0.353 Tl.sub.0.33Pt.sub.0.67 .fwdarw. 0.12 PtO.sub.2 + 0.058 Tl.sub.2Pt.sub.2O.sub.7 0.916 1.093 −1.050 0.944 Bi 0.327 O.sub.2 + 0.346 Bi.sub.0.33Pt.sub.0.67 .fwdarw. 0.118 PtO.sub.2 + 0.038 Bi.sub.3Pt.sub.3O.sub.11 0.945 1.060 −1.132 1.018
[0062] Based on the information provided in Tables 8 to 11, a sum of the penalty points (ΣPP) is calculated for each Pt.sub.0.67M.sub.0.33, i.e., ΣPP=PP1+PP2+PP3+PP4+PP5+PP6+PP7. The sum of the penalty points for Pt.sub.0.67Ru.sub.0.33 is 6.330, i.e. ΣPP (Pt.sub.0.67Ru.sub.0.33)=6.330. Table 12 provides a summary of the information in relation to each Pt.sub.0.67M.sub.0.33. Particularly, Table 12 provides a sum of the penalty points (ΣPP) for each Pt.sub.0.67M.sub.0.33. Table 12 further provides the molecular weight (MW) of each Pt.sub.0.67M.sub.0.33, a sum of penalty points of each Pt.sub.0.67M.sub.0.33 per MW (ΣPP per MW), and a percentage (%) of improvement of each Pt.sub.0.67M.sub.0.33 when compared to Pt.sub.0.67Ru.sub.0.33 based on the ΣPP per MW. It is noted that 1PP (Pt.sub.0.67Ru.sub.0.33) per MW is about 38.585. To calculate the percentage of improvement of each Pt.sub.0.67Ru.sub.0.33 when compared to Pt.sub.0.67Ru.sub.0.33 based on the ΣPP per MW, ΣPP (Pt.sub.0.67Ru.sub.0.33) per MW is divided by the ΣPP per MW of each Pt.sub.0.67M.sub.0.33. For example, since 1PP (Pt.sub.0.67Ti.sub.0.33) per MW 82.505, the percentage of improvement of Pt.sub.0.67Ti.sub.0.33 when compared to Pt.sub.0.67Ru.sub.0.33 thus equals 38.585/82.505, which is about 46.8%.
TABLE-US-00012 TABLE 12 A summary of the information in relation to each Pt.sub.0.67M.sub.0.33, where M may be Ti, Ge, Se, Zr, Nb, Mo, Rh, Pd, Ag, Sn, Sb, Ce, Hf, Ta, W, Re, Os, Ir, Au, Tl, or Bi. % of MW ΣPP per improvement M ΣPP (g/mol) MW (mg) per MW (g) Ru 6.330 164.055 38.585 100.0 (reference) Ti 12.087 146.498 82.505 46.8 Ge 7.304 154.673 47.219 81.7 Se 4.876 156.759 31.106 124.0 Zr 12.389 160.806 77.041 50.1 Nb 11.469 161.361 71.077 54.3 Mo 7.435 162.362 45.791 84.3 Rh 5.971 164.661 36.260 106.4 Pd 5.473 165.821 33.008 116.9 Ag 6.052 166.299 36.392 106.0 Sn 6.759 169.877 39.788 97.0 Sb 6.513 170.883 38.111 101.2 Ce 11.959 176.941 67.586 57.1 Hf 12.644 189.604 66.687 57.9 Ta 11.128 190.415 58.443 66.0 W 7.995 191.369 41.776 92.4 Re 7.429 192.151 38.661 99.8 Os 5.464 193.478 28.239 136.6 Ir 5.342 194.134 27.518 140.2 Au 5.760 195.701 29.430 131.1 Tl 5.670 198.149 28.613 134.8 Bi 6.167 199.666 30.885 124.9
[0063]
[0064] Referring to
[0065] Noted that Pt-M alloys having ratios of Pt to M other than 2 may similarly be evaluated using the method described herein. For instance, in some other embodiments, the data-driven materials screening method may be utilized to evaluate Pt-M alloys, such as Pt.sub.0.95M.sub.0.05 or Pt.sub.0.5M.sub.0.5, where M may be Ti, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, Ce, Hf, Ta, W, Re, Os, Ir, Au, Tl, or Bi, to identify those suitable to be used as electrochemical cell anode catalyst materials to prevent cell voltage reversal during H.sub.2 fuel starvation.
[0066] Apart from binary Pt-based alloys, the data-driven materials screening method may further be used to screen ternary Pt-based alloys, i.e. Pt-M.sup.I-M.sup.11, to identify those that are suitable to be used as electrochemical cell anode catalyst materials to prevent cell voltage reversal during H.sub.2 fuel starvation. M.sup.I is a metal element other than Pt, and M.sup.II is also a metal element other than Pt. In some embodiments, the ternary Pt-based alloys may be Pt.sub.xM.sup.I.sub.yM.sup.IIz, where x=2y=6z, x>0, M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-based alloys are Pt.sub.0.6M.sup.I.sub.0.3M.sup.II.sub.0.1, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In some other embodiments, the ternary Pt-based alloys may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=6y=2z, x>0, M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-based alloys are Pt.sub.0.6M.sup.I.sub.0.1M.sup.II.sub.0.3, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In yet some other embodiments, the ternary Pt-based alloys may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x+y+z=1, 0<x<0.5, 0<y<0.5, 0<z<0.5, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Ti, Au, Bi, Se, or Pd.
[0067] Table 13 provides a summary of information of some exemplary Pt-M.sup.I-M.sup.II. Table 13 provides a sum of penalty points (ΣPP′) for each Pt-M.sup.I-M.sup.11. Table 13 further provides the molecular weight (MW) of each Pt-M.sup.I-M.sup.II, a sum of penalty points of each Pt-M.sup.I-M.sup.II per MW (ΣPP′ per MW), and a percentage (%) of improvement of each Pt-M.sup.I-M.sup.II when compared to Pt.sub.0.67Ru.sub.0.33 based on the ΣPP′ per MW. It is noted that 1PP (Pt.sub.0.67Ru.sub.0.33) per MW is about 38.585. To calculate the percentage of improvement of each Pt-M.sup.I-M.sup.II when compared to Pt.sub.0.67Ru.sub.0.33 based on the ΣPP′ per MW, ΣPP (Pt.sub.0.67Ru.sub.0.33) per MW is divided by the ΣPP′ per MW of each Pt-M.sup.I-M.sup.11. For example, since 1PP′ (Pt.sub.0.6Ru.sub.0.3Ir.sub.0.1) per MW 35.841, the percentage of improvement of Pt.sub.0.6Ru.sub.0.3Ir.sub.0.1 when compared to Pt.sub.0.67Ru.sub.0.33 thus equals 38.585/35.841, which is about 107.7%.
TABLE-US-00013 TABLE 13 A summary of information of exemplary Pt-M.sup.I-M.sup.II. % of MW ΣPP′ per improvement Composition ΣPP′ (g/mol) MW (mg) per MW (g) Ru (reference) 6.330 164.055 38.585 100.0 Pt.sub.0.6Ru.sub.0.3Ir.sub.0.1 5.971 166.590 35.841 107.7 Pt.sub.0.6Ge.sub.0.3Se.sub.0.1 7.317 146.735 49.865 77.4 Pt.sub.0.6Ge.sub.0.3Bi.sub.0.1 8.440 159.737 52.839 73.0 Pt.sub.0.6Mo.sub.0.3Se.sub.0.1 8.095 153.725 52.662 73.3 Pt.sub.0.6Mo.sub.0.3Bi.sub.0.1 8.823 166.727 52.919 72.9 Pt.sub.0.6Ge.sub.0.1Se.sub.0.3 5.939 147.999 40.129 96.2 Pt.sub.0.6Ge.sub.0.1Bi.sub.0.3 8.386 187.005 44.846 86.0 Pt.sub.0.6Mo.sub.0.1Se.sub.0.3 6.126 150.329 40.751 94.7 Pt.sub.0.6Mo.sub.0.1Bi.sub.0.3 7.709 189.335 40.718 94.8
[0068] In view of the foregoing, Pt-based alloys that are comparatively effective as Pt—Ru to be used as electrochemical cell anode catalyst materials may be a binary Pt-M alloy, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Tl or Bi. In some embodiments, the binary Pt-M alloy may be Pt.sub.xM.sub.y, where x=2y, x>0, and M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Tl or Bi. For example, the binary Pt-M alloy is Pt.sub.0.67M.sub.0.33, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. In some other embodiments, the binary Pt-M alloy may be Pt.sub.0.95M.sub.0.05, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. In yet some other embodiments, the binary Pt-M alloy may be Pt.sub.0.5M.sub.0.5, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi.
[0069] The Pt-based alloys may also be a ternary Pt-M.sup.I-M.sup.II alloy, where M.sup.I is a metal element other than Pt, and M.sup.II is also a metal element other than Pt. In some embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=2y=6z, x>0, M.sup.I may be Ru, Ge, or Mo, and Mu may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.0.6M.sup.I.sub.0.3M.sup.II.sub.0.1, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In some other embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=6y=2z, x>0, M.sup.I may be Ru, Ge, or Mo, and M may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.0.6M.sup.I.sub.0.1M.sup.II.sub.0.3, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In yet some other embodiments, the ternary Pt-based alloys may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x+y+z=1, 0<x<0.5, 0<y<0.5, 0<z<0.5, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
[0070] Either the binary or ternary Pt-based alloys may further be mixed with Ir, Ru and/or an Ir—Ru alloy. Either the binary or ternary Pt-based alloys may also be mixed with Ir- or Ru-containing oxides, such as IrO.sub.2, RuO.sub.2, and/or Ir—Ru—O. Ir—Ru—O is a metal oxide of Ir and Ru.
[0071] To synthesize a Pt-based alloy catalyst, Pt may be annealed with stoichiometric amounts of other metal element precursors under a reducing heat treatment condition (e.g. under a nitrogen (N.sub.2), argon (Ar), or H.sub.2 gas atmosphere). Depending on the alloy, a heat treatment temperature may be in a range of 150 and 1,000° C., and a heat treatment time may be in a range of 30 seconds and 24 hours.
[0072] The loss of ECSA of a Pt-based alloy catalyst may be determined using a potentiostat with either a triangular or square wave having a voltage up to 0.9 V. In some embodiments, to understand catalyst degradation induced by carbon corrosion, the voltage may be further up to 1.5 V. When determining the loss of ECSA, H.sub.2 may be used to measure an amount of the adsorbed or desorbed gas. For a more accurate determination of the loss of ECSA, a carbon monoxide stripping method may be utilized. In addition, mass activity measurements of the Pt-based alloy catalyst may be performed in a rotating disk electrode (RDE) or using a full membrane-electrode-assembly (MEA) setup under H.sub.2 or O.sub.2 atmosphere.
[0073] Referring back to
[0074] The Pt-based alloy may also be a ternary Pt-M.sup.I-M.sup.II alloy, where M.sup.I is a metal element other than Pt, and M.sup.II is also a metal element other than Pt. In some embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=2y=6z, x>0, M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.0.6M.sup.I.sub.0.3M.sup.II.sub.0.1, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In some other embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=6y=2z, x>0, M.sup.I may be Ru, Ge, or Mo, and M may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.0.6M.sup.I.sub.0.1M.sup.II.sub.0.3, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In yet some other embodiments, the ternary Pt-based alloys may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x+y+z=1, 0<x<0.5, 0<y<0.5, 0<z<0.5, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd.
[0075] Either the binary or ternary Pt-based alloys may also be mixed with Ir- or Ru-containing oxides, such as IrO.sub.2, RuO.sub.2, and/or Ir—Ru—O. Ir—Ru—O is a metal oxide of Ir and Ru. Either the binary or ternary Pt-based alloys may be nanoparticles having an average size in a range of 1 and 20 nm.
[0076] Continuing referring to
[0077] Individual PEM fuel cells may be assembled into a fuel cell stack. Each fuel cell in the stack is sandwiched between two flow field plates which separate each fuel cell from neighboring fuel cells. In a fuel cell stack, cell voltages of individual fuel cells may be different depending on the location of each fuel cell in the fuel cell stack. Different cell voltages may induce different degradations upon the catalyst performance in each fuel cell. For example, fuel cells that are positioned near a reactant inlet of the fuel cell stack may degrade faster than the ones positioned in a middle area of the fuel cell stack. Therefore, to improve the performance and durability of a fuel cell stack, catalyst materials of a PEM fuel cell may be varied based on its location in the fuel cell stack.
[0078]
[0079] Referring to
[0080] At least one fuel cell, for example, fuel cell X, in the first region 80 may include an MEA with a first anode catalyst material on an anode layer of the fuel cell X. Similarly, at least one fuel cell, for example, fuel cell Z, in the second region 90 may include an MEA with a second anode catalyst material on an anode layer of the fuel cell Z. Likewise, at least one fuel cell, for example, fuel cell Y, in the third region 100 may include an MEA with a third anode catalyst material on an anode layer of the fuel cell Y. According to the locations of fuel cells X, Y and Z in the fuel cell stack 70, at least one of the first, second, and third anode catalyst materials are different.
[0081] To prevent cell voltage reversal during H.sub.2 fuel starvation, the first anode catalyst material in fuel cell X may include a first Pt-based alloy. The first Pt-based alloy may be a binary Pt-M alloy, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Tl or Bi. In some embodiments, the binary Pt-M alloy may be Pt.sub.xM.sub.y, where x=2y, x>0, and M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Tl or Bi. For example, the binary Pt-M alloy is Pt.sub.0.67M.sub.0.33, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Tl or Bi. In some other embodiments, the binary Pt-M alloy may be Pt.sub.0.95M.sub.0.05, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Tl or Bi. In yet some other embodiments, the binary Pt-M alloy may be Pt.sub.0.5M.sub.0.5, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Tl or Bi. The first Pt-based alloy may also be a ternary Pt-M.sup.I-M.sup.II alloy. In some embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=2y=6z, x>0, M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.0.6M.sup.I.sub.0.3M.sup.II.sub.0.1, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In some other embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=6y=2z, x>0, M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.0.6M.sup.I.sub.0.1M.sup.II.sub.0.3, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In yet some other embodiments, the ternary Pt-based alloys may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x+y+z=1, 0<x<0.5, 0<y<0.5, 0<z<0.5, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd. The first Pt-based alloy may further be mixed with Ir, Ru and/or an Ir—Ru alloy. The first Pt-based alloy may also be mixed with Ir- or Ru-containing oxides, such as IrO.sub.2, RuO.sub.2, and/or Ir—Ru—O. Ir—Ru—O is a metal oxide of Ir and Ru. The first Pt-based alloy may be a nanoparticle having an average size in a range of 1 and 20 nm.
[0082] The second anode catalyst material in fuel cell Z may include a second Pt-based alloy. The second Pt-based alloy may be a binary Pt-M alloy, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. In some embodiments, the binary Pt-M alloy may be Pt.sub.xM.sub.y, where x=2y, x>0, and M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. For example, the binary Pt-M alloy is Pt.sub.0.67M.sub.0.33, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. In some other embodiments, the binary Pt-M alloy may be Pt.sub.0.95M.sub.0.05, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. In yet some other embodiments, the binary Pt-M alloy may be Pt.sub.0.5M.sub.0.5, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. The second Pt-based alloy may also be a ternary Pt-M.sup.I-M.sup.II alloy. In some embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=2y=6z, x>0, M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.0.6M.sup.I.sub.0.3M.sup.II.sub.0.1, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In some other embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=6y=2z, x>0, M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.0.6M.sup.I.sub.0.1M.sup.II.sub.0.3, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In yet some other embodiments, the ternary Pt-based alloys may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x+y+z=1, 0<x<0.5, 0<y<0.5, 0<z<0.5, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Ti, Au, Bi, Se, or Pd. The second Pt-based alloy may further be mixed with Ir, Ru and/or an Ir—Ru alloy. The second Pt-based alloy may also be mixed with Ir- or Ru-containing oxides, such as IrO.sub.2, RuO.sub.2, and/or Ir—Ru—O. Ir—Ru—O is a metal oxide of Ir and Ru. The second Pt-based alloy may be a nanoparticle having an average size in a range of 1 and 20 nm.
[0083] The third anode catalyst material in fuel cell Y may include a third Pt-based alloy. The third Pt-based alloy may be a binary Pt-M alloy, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. In some embodiments, the binary Pt-M alloy may be Pt.sub.xM.sub.y, where x=2y, x>0, and M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. For example, the binary Pt-M alloy is Pt.sub.0.67M.sub.0.33, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. In some other embodiments, the binary Pt-M alloy may be Pt.sub.0.95M.sub.0.05, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. In yet some other embodiments, the binary Pt-M alloy may be Pt.sub.0.5M.sub.0.5, where M may be Ge, Se, Mo, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Au, Ti or Bi. The third Pt-based alloy may also be a ternary Pt-M.sup.I-M.sup.II alloy. In some embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=2y=6z, x>0, M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-M.sup.I-M.sup.II alloy is Pt.sub.0.6M.sup.I.sub.0.3M.sup.II.sub.0.1, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In some other embodiments, the ternary Pt-M.sup.I-M.sup.II alloy may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x=6y=2z, x>0, M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. For example, the ternary Pt-alloy is Pt.sub.0.6M.sup.I.sub.0.1M.sup.II.sub.0.3, where M.sup.I may be Ru, Ge, or Mo, and M.sup.II may be Ir, Os, Tl, Au, Bi, Se, or Pd. In yet some other embodiments, the ternary Pt-based alloys may be Pt.sub.xM.sup.I.sub.yM.sup.II.sub.z, where x+y+z=1, 0<x<0.5, 0<y<0.5, 0<z<0.5, M.sup.I is Ru, Ge, or Mo, and M.sup.II is Ir, Os, Tl, Au, Bi, Se, or Pd. The third Pt-based alloy may further be mixed with Ir, Ru and/or an Ir—Ru alloy. The third Pt-based alloy may also be mixed with Ir- or Ru-containing oxides, such as IrO.sub.2, RuO.sub.2, and/or Ir—Ru—O. Ir—Ru—O is a metal oxide of Ir and Ru. The third Pt-based alloy may be a nanoparticle having an average size in a range of 1 and 20 nm.
[0084] Continuing referring to
[0085] In addition to catalyst materials, catalyst loadings may also influence catalytic activities of a fuel cell stack. High catalyst loadings may extend a lifetime of the fuel cell stack and consequently boost the fuel cell stack performance. On the other hand, low catalyst loadings may accelerate catalyst consumption and affect fuel cell performance. Therefore, besides varying the anode catalyst materials according to the locations of the fuel cells in the fuel cell stack, dynamically allocating catalyst loadings in the fuel cells according to the locations of the fuel cells in the fuel cell stack may further improve the performance and durability of the fuel cell stack.
[0086] Apart from catalyst materials and catalyst loadings, other factors may also influence the performance and durability of the fuel cell stack. Some of these factors may include ionomers used in the MEAS of the fuel cells in the fuel cell stack. Therefore, varying the ionomers in the fuel cells based on the locations of the fuel cells in the fuel cell stack may also improve the performance and durability of the fuel cell stack.
[0087] Noted that a catalyst support, such as an anode catalyst support, may not be required for some types of electrochemical cells, such as electrolyzers.
[0088] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the present disclosure that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications.