ANODE CATALYST LAYER OF MEMBRANE ELECTRODE ASSEMBLY AND PREPARATION METHOD THEREOF

Abstract

An anode catalyst layer for a membrane electrode assembly including 30-43 wt % of an anode catalyst, 10-20 wt % of an ionomer solution, 0.02-0.04 wt % of a multidimensional carbon material, and 0.3-0.4 wt % of a multi-walled carbon nanotube is provided. A method for preparing the anode catalyst layer, the membrane electrode assembly that is prepared using the anode catalyst layer, and a method for preparing the membrane electrode assembly are also provided.

Claims

1. An anode catalyst layer for a membrane electrode assembly, the anode catalyst layer comprising: 30-43 wt % of an anode catalyst; 10-20 wt % of an ionomer solution; 0.02-0.04 wt % of a multidimensional carbon material; and 0.3-0.4 wt % of a multi-walled carbon nanotube, wherein the anode catalyst is PbO.sub.2, Pb.sub.3O.sub.4, or a combination thereof.

2. The anode catalyst layer for the membrane electrode assembly according to claim 1, wherein the anode catalyst is a combination of PbO.sub.2 and Pb.sub.3O.sub.4 in a weight ratio from 10:1 to 1:10.

3. The anode catalyst layer for the membrane electrode assembly according to claim 1, wherein the multidimensional carbon material is graphene, graphene oxide, reduced graphene oxide, or any combination thereof.

4. The anode catalyst layer for the membrane electrode assembly according to claim 1, further comprising: 2-6 wt % of a hydrophobic solution; 3-10 wt % of an acidic solution; and 30-40 wt % of deionized water.

5. The anode catalyst layer for the membrane electrode assembly according to claim 4, wherein the anode catalyst is a combination of PbO.sub.2 and Pb.sub.3O.sub.4 in a weight ratio from 10:1 to 1:10.

6. The anode catalyst layer for the membrane electrode assembly according to claim 4, wherein the multidimensional carbon material is graphene, graphene oxide, reduced graphene oxide, or any combination thereof.

7. A method for preparing an anode catalyst layer for a membrane electrode assembly, the method comprising: mixing 30-40 wt % of deionized water with an ionomer solution, a hydrophobic solution, and an acidic solution to form a first mixture; adding 30-43 wt % of an anode catalyst, a multi-walled carbon nanotube, and a multidimensional carbon material to the first mixture to form a second mixture; rotating the second mixture at 15000-18000 rpm for 30-50 minutes to form a homogeneous coating; and applying the homogeneous coating to a transfer substrate and drying at 25-30 C. for 10-15 minutes.

8. The method according to claim 7, wherein the ionomer solution is 10-20 wt %, the hydrophobic solution is 2-6 wt %, the acidic solution is 3-10 wt %, the multi-walled carbon nanotube is 0.3-0.4 wt %, and the multidimensional carbon material is 0.02-0.04 wt %.

9. A membrane electrode assembly comprising the anode catalyst layer according to claim 1.

10. A method for preparing a membrane electrode assembly, the method comprising: sequentially stacking a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer according to claim 1 to form the membrane electrode assembly; and hot-pressing the membrane electrode assembly at 120-140 C. under 20-60 kgf/cm.sup.2 for 2 minutes.

11. The method according to claim 10, wherein the anode catalyst layer has a loading per unit area of 30-60 mg/cm.sup.2.

12. A method for preparing a membrane electrode assembly, the method comprising: sequentially stacking a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer according to claim 4 to form the membrane electrode assembly; and hot-pressing the membrane electrode assembly at 120-140 C. under 20-60 kgf/cm.sup.2 for 2 minutes.

13. The method according to claim 12, wherein the anode catalyst layer has a loading per unit area of 30-60 mg/cm.sup.2.

14. A method for preparing a membrane electrode assembly, the method comprising: mixing 30-40 wt % of deionized water with an ionomer solution, a hydrophobic solution, and an acidic solution to form a first mixture; adding 30-43 wt % of an anode catalyst, a multi-walled carbon nanotube, and a multidimensional carbon material to the first mixture to form a second mixture; rotating the second mixture at 15000-18000 rpm for 30-50 minutes to form a homogeneous coating; applying the homogeneous coating to a transfer substrate and drying at 25-30 C. for 10-15 minutes to form an anode catalyst layer; sequentially stacking a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly; hot-pressing the membrane electrode assembly at 120-140 C. under 20-60 kgf/cm.sup.2 for 2 minutes; and removing the transfer substrate.

15. The method according to claim 14, wherein the ionomer solution is 10-20 wt %, the hydrophobic solution is 2-6 wt %, the acidic solution is 3-10 wt %, the multi-walled carbon nanotube is 0.3-0.4 wt %, and the multidimensional carbon material is 0.02-0.04 wt %.

16. The method according to claim 14, wherein the anode catalyst layer has a loading per unit area of 30-60 mg/cm.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] When read in conjunction with the accompanying drawings, the following detailed description will provide a better understanding of the present disclosure, in which:

[0020] FIGS. 1A to E are images showing structures of various anode catalyst layers for membrane electrode assemblies under a scanning electron microscope according to one implementation of the present disclosure.

[0021] FIG. 2 is a schematic diagram illustrating a performance testing configuration for the membrane electrode assemblies according to one implementation of the present disclosure.

[0022] FIG. 3 shows results of long-term constant voltage tests for various membrane electrode assemblies according to one implementation of the present disclosure.

[0023] FIG. 4 shows results of variable voltage tests for various membrane electrode assemblies according to one implementation of the present disclosure.

[0024] FIG. 5 shows results of power interruption and recovery degradation tests for various membrane electrode assemblies according to one implementation of the present disclosure.

[0025] FIG. 6 shows structures and analysis of various anode catalyst layers for membrane electrode assemblies under a scanning electron microscope according to another implementation of the present disclosure.

[0026] FIG. 7 shows X-ray diffraction analysis results of various anode catalyst layers for membrane electrode assemblies according to another implementation of the present disclosure.

[0027] FIG. 8 is a schematic diagram illustrating the performance testing configuration for the membrane electrode assemblies according to another implementation of the present disclosure.

[0028] FIG. 9 shows results of constant current electrolysis performance tests for the membrane electrode assembly according to another implementation of the present disclosure.

[0029] FIGS. 10A and 10B show the results of long-term stability tests for the membrane electrode assembly according to another implementation of the present disclosure.

DETAILED DESCRIPTION

[0030] The following description contains specific information about illustrative implementations of the present disclosure. The accompanying drawings and their detailed descriptions in the present disclosure are only for these illustrative implementations. However, the present disclosure is not limited to these illustrative implementations. Those skilled in the art will recognize other variations and implementations of the present disclosure.

[0031] Terms such as at least one implementation, an implementation, multiple implementations, different implementations, some implementations, the present implementation, etc., may indicate that the described implementations of the present disclosure may include specific features, compositions, or characteristics, but not every possible implementation of the present disclosure must include the specific features, compositions, or characteristics. Furthermore, repeated use of phrases such as in an implementation, in the present implementation does not necessarily refer to the same implementation, although they may. Moreover, the use of phrases such as implementation in association with the present disclosure does not mean that all implementations of the present disclosure must include the specific features, compositions, or characteristics, and should be understood as at least some implementations of the present disclosure include the stated specific features, compositions, or characteristics.

[0032] The terms first, second, third, etc. in the specification and the above drawings of the present disclosure are only used to distinguish different objects, not to describe a specific order.

[0033] The term include(s) and any of its variations in the specification and the above drawings of the present disclosure are intended to cover a non-exclusive inclusion, explicitly indicating an open-ended inclusion or relationship of the stated combinations, groups, series, and equivalents. For example, a process, method, system, product, or equipment that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally include unlisted steps or modules, or may optionally include other steps or modules inherent to these processes, methods, products, or equipment.

[0034] Additionally, for the purpose of interpretation and not limitation, specific details such as functional entities, technologies, protocols, standards, etc. are elaborated to provide an understanding of the described technology. In other examples, detailed descriptions of well-known methods, techniques, systems, architectures, etc. are omitted for brevity.

[0035] The present disclosure provides an anode catalyst layer for a membrane electrode assembly, which may include 30-43 wt % of anode catalysts, 10-20 wt % of ionomer solution, 0.02-0.04 wt % of multidimensional carbon materials, and 0.3-0.4 wt % of multi-walled carbon nanotubes. The anode catalyst layer for the membrane electrode assembly of the present disclosure may further include 2-6 wt % of hydrophobic solution, 3-10 wt % of acidic solution, and 30-40 wt % of deionized water.

[0036] In some implementations, the anode catalyst may be lead dioxide (PbO.sub.2), lead tetroxide (Pb.sub.3O.sub.4), or a combination thereof. In a preferred implementation, the anode catalyst may be a combination of lead dioxide and lead tetroxide in a weight ratio from 10:1 to 1:10.

[0037] In some implementations, the ionomer solution may be a perfluorosulfonic acid (PFSA) polymer (such as Nafion), tetrafluoroethylene-perfluoro (3-oxa-4-pentenesulfonic acid) copolymer, short-side-chain perfluorinated sulfonic acid/PTFE copolymer in the SO.sub.3H form, or any combination thereof.

[0038] In some implementations, the multidimensional carbon material may be graphene, graphene oxide, reduced graphene oxide, or any combination thereof.

[0039] In some implementations, the hydrophobic solution may be polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP) dispersion, polydimethylsiloxane (PDMS), or any combination thereof.

[0040] In some implementations, the acidic solution may be sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, or any combination thereof.

[0041] The present disclosure also provides a method for preparing the anode catalyst layer for a membrane electrode assembly, which is mainly by preparing the anode catalyst layer according to the above weight percentages of each material. The specific preparation may include: (a) taking the 30-40 wt % of deionized water, and sequentially adding the ionomer solution, the hydrophobic solution, and the acidic solution to form a first mixture; (b) sequentially adding the 30-43 wt % of anode catalysts, the multi-walled carbon nanotubes, and the multidimensional carbon materials to the first mixture to form a second mixture; (c) rotating the second mixture at 15000-18000 rpm for 30-50 minutes to form a homogeneous coating; and (d) applying the homogeneous coating to a transfer substrate and drying at 25-30 C. for 10-15 minutes.

[0042] In some implementations, the ionomer solution may account for 10-20 wt % of the total weight. In some implementations, the hydrophobic solution may account for 2-6 wt % of the total weight. In some implementations, the acidic solution may account for 3-10 wt % of the total weight. In some implementations, the multi-walled carbon nanotubes may account for 0.3-0.4 wt % of the total weight. In some implementations, the multidimensional carbon material may account for 0.02-0.04 wt % of the total weight.

[0043] In some implementations, the multi-walled carbon nanotubes and the multidimensional carbon materials may be first prepared as a mixed powder before being added to the first mixture. The mixed powder may be prepared by first mixing the multi-walled carbon nanotubes and the multidimensional carbon materials with an ethylene glycol aqueous solution in a 1:1 weight ratio, then subjecting the mixture to ultrasonic vibration for 2 hours followed by stirring at a constant temperature of 80 C. for 24 hours, and finally, the powder may be extracted by centrifugation and dried at 80 C. for 12 hours.

[0044] In some implementations, the transfer substrate may be glass fiber paper, polyimide (Kapton), polytetrafluoroethylene sheet (Teflon sheet), aluminum foil, or any combination thereof.

[0045] The present disclosure also provides a membrane electrode assembly, which mainly includes the above anode catalyst layer containing materials in specific weight percentages. The membrane electrode assembly of the present disclosure may be based on solid polymer electrolyte technology, where an anode catalyst layer and a cathode catalyst layer are attached to both sides of a solid electrolyte to form a membrane electrode assembly.

[0046] In some implementations, the solid electrolyte may be a polymer membrane with proton transmission capability, for example, the solid electrolyte may be a perfluorinated sulfonic acid polymer membrane (such as Nafion, Aciplex), a partially fluorinated sulfonated polymer membrane (such as BAM3G), a non-fluorinated sulfonated polymer membrane (such as sulfonated polyimide, sulfonated aromatic backbone, polystyrene), or related or derived composite structures. In some implementations, the cathode catalyst layer may be an electrode composed of platinum-based (Pt/C) or molybdenum-based (CoMoS) catalysts combined with porous and gas-liquid diffusion transport substrates such as carbon cloth, titanium felt, or titanium plate.

[0047] The present disclosure also provides a method for preparing a membrane electrode assembly, including: (a) sequentially stacking a cathode catalyst electrode (or layer), a solid electrolyte membrane, and the above anode catalyst layer (or electrode) to form a membrane electrode assembly; and (b) hot-pressing the membrane electrode assembly at 120-140 C. under 20-60 kgf/cm.sup.2 for 2 minutes.

[0048] In some implementations, the method for preparing the membrane electrode assembly of the present disclosure may more specifically include: (a) taking the 30-40 wt % of deionized water, and sequentially adding the ionomer solution, the hydrophobic solution, and the acidic solution to form a first mixture; (b) sequentially adding the 30-43 wt % of anode catalysts, the multi-walled carbon nanotubes, and multidimensional carbon materials to the first mixture to form a second mixture; (c) rotating the second mixture at 15000-18000 rpm for 30-50 minutes to form a homogeneous coating; (d) applying the homogeneous coating to a transfer substrate and drying at 25-30 C. for 10-15 minutes to form an anode catalyst layer; (e) sequentially stacking a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly; (f) hot-pressing the membrane electrode assembly at 120-140 C. under 20-60 kgf/cm.sup.2 for 2 minutes; and (g) removing the transfer substrate.

[0049] In some implementations, the ionomer solution may account for 10-20 wt % of the total weight. In some implementations, the hydrophobic solution may account for 2-6 wt % of the total weight. In some implementations, the acidic solution may account for 3-10 wt % of the total weight. In some implementations, the multi-walled carbon nanotubes may account for 0.3-0.4 wt % of the total weight. In some implementations, the multidimensional carbon material may account for 0.02-0.04 wt % of the total weight.

[0050] In some implementations, the anode catalyst layer may have a loading per unit area of 30-60 (mg/cm.sup.2), which may be adjusted based on practical requirements, such as electrode lifespan and gas concentration. In some preferred implementations, the anode catalyst layer may have a loading per unit area of 35 (mg/cm.sup.2).

[0051] The following provides further description of the present disclosure through several examples, but the present disclosure is not limited to these examples.

Example 1: Preparing Membrane Electrode Assembly with PbO.SUB.2 .Alone as Anode Catalyst

1.1 Test Group: Preparing Membrane Electrode Assembly with Graphene as a Multidimensional Carbon Material

[0052] Take 37 wt % of deionized water, and sequentially add 20 wt % of PFSA Dispersion ionomer solution (e.g., Nafion), 4 wt % of PTFE hydrophobic solution, and 6 wt % of 0.5M sulfuric acid solution. Then sequentially add 32 wt % of commercially available 97% lead dioxide (Thermo Scientific; product NO: 217535000), 0.32 wt % of multi-walled carbon nanotubes, and 0.035 wt % of graphene. Spin a container filled with the mixture by a centrifuge at 18000 rpm for 30 minutes to form a homogeneous coating, apply the homogeneous coating to a transfer substrate, dry the homogeneous coating with the substrate at 30 C. for 10 minutes to form the anode catalyst layer. Next, sequentially stack a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly, where the anode catalyst layer has a loading per unit area of 35 (mg/cm.sup.2). Then hot-press the membrane electrode assembly at 135 C. under 25 kgf/cm.sup.2 for 2 minutes, and remove the transfer substrate to complete the membrane electrode assembly, hereinafter referred to as Pb+M+G.

1.2 Test Group: Preparing Membrane Electrode Assembly with Graphene Oxide as a Multidimensional Carbon Material

[0053] Take 37 wt % of deionized water, and sequentially add 20 wt % of PFSA Dispersion ionomer solution (e.g., Nafion), 4 wt % of PTFE hydrophobic solution, and 6 wt % of 0.5M sulfuric acid solution. Then sequentially add 32 wt % of commercially available 97% lead dioxide (Thermo Scientific; product NO: 217535000), 0.32 wt % of multi-walled carbon nanotubes, and 0.035 wt % of graphene oxide. Spin a container filled with the mixture by a centrifuge at 18000 rpm for 30 minutes to form a homogeneous coating, apply the homogeneous coating to a transfer substrate, dry the homogeneous coating with the substrate at 30 C. for 10 minutes to form the anode catalyst layer. Next, sequentially stack a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly, where the anode catalyst layer has a loading per unit area of 35 (mg/cm.sup.2). Then hot-press the membrane electrode assembly at 135 C. under 25 kgf/cm.sup.2 for 2 minutes, and remove the transfer substrate to complete the membrane electrode assembly, hereinafter referred to as Pb+M+GO.

1.3 Test Group: Preparing Membrane Electrode Assembly with Reduced Graphene Oxide as a Multidimensional Carbon Material

[0054] Take 37 wt % of deionized water, and sequentially add 20 wt % of PFSA Dispersion ionomer solution (e.g., Nafion), 4 wt % of PTFE hydrophobic solution, and 6 wt % of 0.5M sulfuric acid solution. Then sequentially add 32 wt % of commercially available 97% lead dioxide (Thermo Scientific; product NO: 217535000), 0.32 wt % of multi-walled carbon nanotubes, and 0.035 wt % of reduced graphene oxide. Spin a container filled with the mixture by a centrifuge at 18000 rpm for 30 minutes to form a homogeneous coating, apply the homogeneous coating to a transfer substrate, dry the homogeneous coating with the substrate at 30 C. for 10 minutes to form the anode catalyst layer. Next, sequentially stack a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly, where the anode catalyst layer has a loading per unit area of 35 (mg/cm.sup.2). Then hot-press the membrane electrode assembly at 135 C. under 25 kgf/cm.sup.2 for 2 minutes, and remove the transfer substrate to complete the membrane electrode assembly, hereinafter referred to as Pb+M+RGO.

1.4 Control Group: Preparing Membrane Electrode Assembly without Multi-Walled Carbon Nanotubes or a Multidimensional Carbon Material

[0055] Take 37 wt % of deionized water, and sequentially add 20 wt % of PFSA Dispersion ionomer solution (e.g., Nafion), 4 wt % of PTFE hydrophobic solution, and 6 wt % of 0.5M sulfuric acid solution. Then sequentially add 32 wt % of commercially available 97% lead dioxide (Thermo Scientific; product NO: 217535000), and 0.4-0.8 wt % of multi-walled carbon nanotubes (e.g., 0.6 wt % may be used). Spin a container filled with the mixture by a centrifuge at 18000 rpm for 30 minutes to form a homogeneous coating, apply the homogeneous coating to a transfer substrate, dry the homogeneous coating with the substrate at 30 C. for 10 minutes to form the anode catalyst layer. Next, sequentially stack a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly, where the anode catalyst layer has a loading per unit area of 35 (mg/cm.sup.2). Then hot-press the membrane electrode assembly at 135 C. under 25 kgf/cm.sup.2 for 2 minutes, and remove the transfer substrate to complete the membrane electrode assembly, hereinafter referred to as Pb+M.

[0056] Take 38 wt % of deionized water, and sequentially add 20 wt % of PFSA Dispersion ionomer solution (e.g., Nafion), 4 wt % of PTFE hydrophobic solution, and 6 wt % of 0.5M sulfuric acid solution. Then sequentially add 32 wt % of commercially available 97% lead dioxide (Thermo Scientific; product NO: 217535000). Spin a container filled with the mixture by a centrifuge at 18000 rpm for 30 minutes to form a homogeneous coating, apply the homogeneous coating to a transfer substrate, dry the homogeneous coating with the substrate at 30 C. for 10 minutes to form the anode catalyst layer. Next, sequentially stack a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly, where the anode catalyst layer has a loading per unit area of 35 (mg/cm.sup.2). Then hot-press the membrane electrode assembly at 135 C. under 25 kgf/cm.sup.2 for 2 minutes, and remove the transfer substrate to complete the membrane electrode assembly, hereinafter referred to as Pb.

[0057] The anode catalyst layers of the above membrane electrode assemblies Pb, Pb+M, Pb+M+G, Pb+M+GO, and Pb+M+RGO are observed using a scanning electron microscope, with results shown in FIGS. 1A to 1E, wherein lead dioxide is indicated by black dotted lines, multi-walled carbon nanotubes by black solid lines, and multidimensional carbon materials by black dashed lines. FIG. 1A shows that the anode catalyst layer containing only lead oxide has a dense surface, which would reduce the reaction area. FIG. 1B shows that the anode catalyst layer containing multi-walled carbon nanotubes has a lower density and a larger volume and forms a macroporous structure due to its cylindrical shape, which would result in high electrical conductivity and mass ratio. FIGS. 1C to E show that in the anode catalyst layers containing multidimensional conductive carbon materials, when used in conjunction with multi-walled carbon nanotubes, the multidimensional conductive carbon materials may cover the catalyst surface and enhance bonding ability, thus promoting the formation of microelectronic conduction channels between the microporous channels that are formed by the multi-walled carbon nanotubes, and further improving conductivity.

[0058] Furthermore, the above membrane electrode assemblies Pb, Pb+M, Pb+M+G, Pb+M+GO, and Pb+M+RGO undergo performance tests including long-term constant voltage tests, variable voltage tests, and power interruption and recovery degradation tests with the experimental configuration, as shown in FIG. 2. The experimental configuration involves loading the membrane electrode assembly into a supporting mechanism and providing circuit and waterway connection points to enable operation of the membrane electrode assembly. The circuit is connected to a programmable power supply to provide energy and controls the voltage output and open/closed circuit states according to test conditions. The waterway is connected to a water tank including temperature control equipment, which maintains the water temperature at a constant 20 C., with deionized water supplied only to the anode side. The test conditions used for these performance tests are shown in Table 1. The results of the constant voltage, variable voltage, and power interruption and recovery degradation tests are shown in FIGS. 3 to 5, respectively.

TABLE-US-00001 TABLE 1 Activa- Voltage Current Total Operation tion Interrup- Recovery Test Voltage Time tion Time Time Time Constant Voltage 4.5 V 8 h 12 h Variable Voltage 4.5 V/4.0 V 8 h 12 h 3.5 V/3.0 V 2.5 V Power 4.5 V 8 h 0 V/5 min 5 min 29 h Interruption and Recovery

[0059] As shown in FIG. 3, the addition of multi-walled carbon nanotubes enables the membrane electrode assembly to have high conductivity and form a porous structure, which is beneficial for electron and mass transfer, thus improving overall performance. At high voltage (e.g., 4.5V), gas and water exchange rely on the porous structure. Therefore, after adding multidimensional carbon materials, the porosity and microporous channels of multi-walled carbon nanotubes may be further enhanced, thus forming microelectronic conduction channels, and improving the conductivity and performance stability of the anode. The difference in overall performance may reach up to 2 times. Increasing the applied voltage to improve electrolysis performance requires the transport of more gas and water to maintain the electrolysis reaction, thus relying more on the characteristics of the porous structure to enhance a bidirectional transport on the catalyst surface.

[0060] As shown in FIG. 4, the addition of multi-walled carbon nanotubes increases the porous structure, which is beneficial for mass transfer effects, thus enabling stable operation under high-pressure conditions. In contrast, the membrane electrode assembly Pb, which does not use multi-walled carbon nanotubes and multidimensional carbon materials, has fewer porous structures, and thus producing a large amount of gas under high-current operation, and impacting structural stability. The membrane electrode assembly Pb+M+G has carboxyl groups on the surface, which may enhance the hydrophilicity of the membrane electrode, thus facilitating the liquid transport capacity during high reaction performance and continuing the electrochemical reaction. Therefore, the membrane electrode assembly Pb+M+G may demonstrate the highest performance.

[0061] When lead dioxide is used as the anode catalyst, its performance significantly decreases after power interruptions and recovery. Therefore, a test is conducted by running the system at 4.5 V for 700 minutes, interrupting the power for 1 minute, and then recovering to simulate such scenario. The results are shown in FIG. 5. The membrane electrode assembly Pb, which does not use multi-walled carbon nanotubes and multidimensional carbon materials, has a high degradation rate of up to 45%. In contrast, the membrane electrode assemblies Pb+M, Pb+M+G, Pb+M+GO, and Pb+M+RGO show degradation rates of only 34-37%, demonstrating better stability.

[0062] Overall, using the proportions and preparation methods of the present disclosure, the membrane electrode assemblies Pb+M+G, Pb+M+GO, and Pb+M+RGO with added multidimensional carbon materials show enhanced porosity and microporous channels due to the covering of catalysts and strengthened connection characteristics with carbon nanotubes and forming of microelectronic conduction channels, thus further improving the conductivity and performance stability of the anode. The membrane electrode assemblies Pb+M, which only adds multi-walled carbon nanotubes, has a porous and conductive structure that is beneficial for electron and mass transfer effects, thus showing relatively higher performance compared to the those without the additions.

Example 2: Preparing Membrane Electrode Assembly with a Mixture PbO.SUB.2 .and Pb.SUB.3.O.SUB.4 .as an Anode Catalyst

2.1 Test Group: Preparing Membrane Electrode Assembly with Self-Made PbO.sub.2 as Materials

[0063] The method for preparing self-made lead dioxide is as follows: Mix an appropriate amount of lead tetraacetate with glacial acetic acid to form a saturated solution. Then, titrate the saturated solution with an appropriate amount of deionized water and place the titrated solution in an ultrasonic oscillator for 1 hour of vibration. Centrifuge at 4000 rpm for 5 minutes to separate the gel-like product from the liquid. Wash and filter the resulting gel-like product several times with deionized water and alcohols. Then, place the gel-like product in a high-temperature furnace at 70-140 C. for 20 hours to obtain the self-made lead dioxide catalyst powder. The lead dioxide prepared by this method has particle sizes mainly in the range of 30-40 nm, while commercially available lead dioxide is about 200 nm. Furthermore, in terms of lattice structure, the self-made lead dioxide has a slightly higher ratio of lattice oxygen to oxygen vacancies (e.g., 8%), thus enhancing its oxidation capability in water decomposition and its properties for ozone synthesis.

[0064] Take 37 wt % of deionized water, and sequentially add 20 wt % of PFSA Dispersion ionomer solution (e.g., Nafion), 4 wt % of PTFE hydrophobic solution, and 6 wt % of 0.5M sulfuric acid solution. Then sequentially add 32 wt % of the self-made lead dioxide, and 0.4-0.8 wt % of multi-walled carbon nanotubes (e.g., 0.6 wt % may be used). Spin a container filled with the mixture by a centrifuge at 18000 rpm for 30 minutes to form a homogeneous coating, apply the homogeneous coating to a transfer substrate, dry the homogeneous coating with the substrate at 30 C. for 10 minutes to form the anode catalyst layer. Next, sequentially stack a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly, where the anode catalyst layer has a loading per unit area of 35 (mg/cm.sup.2). Then hot-press the membrane electrode assembly at 135 C. under 25 kgf/cm.sup.2 for 2 minutes, and remove the transfer substrate to complete the membrane electrode assembly, hereinafter referred to as HPbO.sub.2.

2.2 Test Group: Preparing Membrane Electrode Assembly with Self-Made Pb.sub.3O.sub.4 as Materials

[0065] The method for preparing self-made lead tetroxide is as follows: Mix an appropriate amount of lead tetraacetate with glacial acetic acid to form a saturated solution. Then, titrate the saturated solution with an appropriate amount of deionized water and place the titrated solution in an ultrasonic oscillator for 1 hour of vibration. Centrifuge at 4000 rpm for 5 minutes to separate the gel-like product from the liquid. Wash and filter the resulting gel-like product several times with deionized water and alcohols. Then, place the gel-like product in a high-temperature furnace at 450-600 C. for 20 hours to obtain the self-made lead tetroxide catalyst powder. The lead tetroxide prepared by this method has particle sizes mainly in the range of 30-40 nm, while commercially available lead tetroxide is about 200 nm. Furthermore, in terms of crystal structure, the self-made lead tetroxide has a slightly higher ratio of lattice oxygen to oxygen vacancies (e.g., 8%), thus enhancing its oxidation capability in water decomposition and its properties for ozone synthesis.

[0066] Take 37 wt % of deionized water, and sequentially add 20 wt % of PFSA Dispersion ionomer solution (e.g., Nafion), 4 wt % of PTFE hydrophobic solution, and 6 wt % of 0.5M sulfuric acid solution. Then sequentially add 32 wt % of the self-made lead tetroxide, and 0.4-0.8 wt % of multi-walled carbon nanotubes (e.g., 0.6 wt % may be used). Spin a container filled with the mixture by a centrifuge at 18000 rpm for 30 minutes to form a homogeneous coating, apply the homogeneous coating to a transfer substrate, dry the homogeneous coating with the substrate at 30 C. for 10 minutes to form the anode catalyst layer. Next, sequentially stack a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly, wherein the anode catalyst layer has a loading per unit area of 35 (mg/cm.sup.2). Then hot-press the membrane electrode assembly at 135 C. under 25 kgf/cm.sup.2 for 2 minutes, and remove the transfer substrate to complete the membrane electrode assembly, hereinafter referred to as HPb.sub.3O.sub.4.

2.3 Test Group: Preparing Membrane Electrode Assembly with Self-Made PbO.sub.2/Pb.sub.3O.sub.4 as Materials

[0067] In such implementation, a mixture of the self-made lead dioxide and lead tetroxide is used as the anode catalyst. Take 37 wt % of deionized water, and sequentially add 20 wt % of PFSA Dispersion ionomer solution (e.g., Nafion), 4 wt % of PTFE hydrophobic solution, and 6 wt % of 0.5M sulfuric acid solution. Then sequentially add 32 wt % of the mixture of the self-made lead dioxide and lead tetroxide, where the mixture may be combined in weight ratios of 2:1, 1:1, or 1:2 (for example, a 1:1 weight ratio mixture of lead dioxide and lead tetroxide may be used), followed by adding 0.4-0.8 wt % of multi-walled carbon nanotubes (e.g., 0.6 wt % may be used). Spin a container filled with the mixture by a centrifuge at 18000 rpm for 30 minutes to form a homogeneous coating, apply the homogeneous coating to a transfer substrate, dry the homogeneous coating with the substrate at 30 C. for 10 minutes to form the anode catalyst layer. Next, sequentially stack a cathode catalyst electrode, a solid electrolyte membrane, and the anode catalyst layer to form a membrane electrode assembly, wherein the anode catalyst layer has a loading per unit area of 35 (mg/cm.sup.2). Then hot-press the membrane electrode assembly at 135 C. under 25 kgf/cm.sup.2 for 2 minutes, and remove the transfer substrate to complete the membrane electrode assemblies, hereinafter referred to as H-Mix (2:1), H-Mix (1:1), or H-Mix (1:2). The membrane electrode assembly H-Mix (1:1) will be used for the following tests.

[0068] The anode catalyst layers of the commercially available (denoted as CPbO.sub.2), the self-made lead dioxide (denoted as HPbO.sub.2), and the self-made lead tetroxide (denoted as HPb.sub.3O.sub.4) membrane electrode assemblies are observed using a scanning electron microscope, with results shown in FIG. 6; wherein units for the field of view of the scanning electron microscope are: CPbO.sub.2 observed at 0.5 m size; HPbO.sub.2 observed at 50 nm size; HPb.sub.3O.sub.4 observed at 200 nm size; the horizontal axis of the rectangular plot represents particle size (nm), and the vertical axis represents cumulative frequency (%). HPbO.sub.2 and HPb.sub.3O.sub.4 have smaller particle sizes, and the spherical structure of HPbO.sub.2 is beneficial for increasing the contact area when stacking catalysts, while CPbO.sub.2 and HPb.sub.3O.sub.4 structures are both similar to a square shape.

[0069] The anode catalyst layers of the above membrane electrode assemblies HPbO.sub.2 and HPb.sub.3O.sub.4 are analyzed using X-ray diffraction, with results shown in FIG. 7, where the diffraction patterns provided by the International Centre for Diffraction Data (ICDD) are used as standards for lead dioxide and lead tetroxide; wherein the horizontal axis represents the incident light reflection angle 20 (degree) and the vertical axis represents intensity (a.u.). Compared with the standards, the catalyst used is -type lead dioxide, with the same lattice pattern as the commercially available catalyst. However, the higher proportion of the 101-lattice plane in HPbO.sub.2 allows lattice oxygen to directly form ozone, thus reducing the energy consumption of ozone synthesis. It is currently known that lead dioxide synthesizes ozone through oxygen atoms within the lattice, and the 101-lattice plane requires the lowest energy for direct synthesis reactions. The diffraction pattern of HPb.sub.3O.sub.4 matches the main characteristic peaks of the standard.

[0070] Furthermore, the above membrane electrode assemblies CPbO.sub.2, HPbO.sub.2, HPb.sub.3O.sub.4, and H-Mix (1:1) undergo performance tests including constant current electrolysis performance tests and long-term stability tests with the experimental configuration as shown in FIG. 9. The experimental configuration involves loading the membrane electrode assembly into a supporting mechanism, providing circuit and waterway connection points to enable operation of the membrane electrode assembly. The circuit is connected to a programmable power supply to provide energy and controls the voltage output and open/closed circuit states according to test conditions. The waterway is connected to a water tank with temperature control equipment, which maintains the water temperature at a constant 20 C., with deionized water supplied only to the anode side. The test conditions used for these performance tests are as shown in Table 2. The results of the constant current electrolysis performance tests are as shown in FIG. 9, while the results of the long-term stability tests are as shown in FIGS. 10A and 10B.

TABLE-US-00002 TABLE 2 Operation Total Test Environmental Current Time Temperature Constant Current 0.25~2 A/cm.sup.2 24 h 20 C. Long-term Stability .sup.2 A/cm.sup.2 100 h

[0071] As shown in FIG. 9, although HPb.sub.3O.sub.4 shows lower constant current electrolysis performance due to the lower catalytic activity of lead tetroxide when compared to lead dioxide, when lead dioxide and lead tetroxide are used in combination, it may enhance the oxygen vacancies in the overall lattice. It is known that lead dioxide catalysts mainly produce ozone through direct coupling oxygen atoms, and thus, increasing oxygen vacancies in the overall lattice may enhance ability of the catalyst surface to adsorb oxygen after water decomposition, thus strengthening the oxidation power and the charge transfer rate. As a result, H-Mix (1:1) exhibits the best performance in constant current electrolysis, thus enhancing the ability to synthesize ozone.

[0072] As shown in FIGS. 10A and 10B, H-Mix (1:1) demonstrates the best long-term stability, thus indicating the lowest degree of performance degradation. This is because lead tetroxide may be converted to lead dioxide through lattice reconstruction, thus replenishing the amount of deactivated lead dioxide catalyst due to continuous reactions. Additionally, HPb.sub.3O.sub.4 also shows mixed valence states and unique electronic structures, which, when compared to commercially available or self-made lead dioxide catalysts, shows excellent stability in long-term stability tests. Therefore, it is expected that combining lead dioxide with lead tetroxide may produce synergistic effects. From these results, it may be anticipated that using different proportions of lead dioxide and lead tetroxide would help in adjusting electrolysis performance and stability to meet the requirements of relevant application fields.

[0073] The present disclosure provides an anode catalyst layer for a membrane electrode assembly and its manufacturing method. The anode catalyst layer is produced by combining a specific proportion of lead dioxide (or a mixture with lead tetroxide) with specific proportions of graphene, ionomer polymer, carbon nanotubes, and pore-forming agents to create the anode catalyst layer, which enhances the electrochemical activity and structural strength of the anode catalyst layer, Thus, addressing the poor mass transfer effects and voltage fluctuation impacts in existing anode catalyst layers, and therefore improving the overall efficiency and stability of the membrane electrode assembly for electrolysis.

[0074] Based on the above description, it is clear that various techniques may be used to implement the concepts described in the present application without departing from the scope of these concepts. Furthermore, although the concepts have been described with specific reference to certain implementations, those skilled in the art will recognize that changes in form and detail may be made without departing from the scope of these concepts. As such, the described implementations should be considered illustrative rather than restrictive in all aspects. Moreover, it should be understood that this application is not limited to the specific implementations described above, but many rearrangements, modifications, and substitutions can be made without departing from the scope of the present disclosure.