METAL COMPOUND, METAL RECOVERY ELECTRODE, AND METHOD FOR RECOVERING METALS FROM SPENT ELECTRODES

Abstract

A method for the electrochemical recovery of a metal from a spent electrode is provided. The method comprises the steps of providing an electrochemical cell comprising a metal recovery electrode as a working electrode, the spent electrode as a counter-electrode, and an electrolyte between the working electrode and the counter-electrode, and performing cyclic voltammetry on the metal recovery electrode, thereby dissolving the metal from the spent electrode and adsorbing dissolved atoms of the metal on the metal recovery electrode, thereby recovering the metal and forming a composite electrode. The metal recovery electrode comprising a metal compound on a conducting support and the metal compound is made by a method comprising reacting a metal oxalate or an ammonium metal oxalate, wherein the metal is a group 4 to 6 metal, with a chalcogenide or an organochalcogenide.

Claims

1. A method of manufacture of a metal compound, the method comprising: reacting a metal carboxylate, wherein the metal is a group 4 to 6 metal, with a chalcogenide or an organochalcogenide.

2. The method of claim 1, wherein the organochalcogenide is an organosulfur.

3. The method of claim 1, wherein the organochalcogenide comprises an amino, carboxylate, carbonyl, or alkyl group.

4. The method of claim 1, wherein the organochalcogenide is thiourea.

5. The method of claim 1, wherein the group 4 to 6 metal is Ti, Zr, Nb, Ta, Hf, Mo, or W.

6. The method of claim 1, wherein the metal carboxylate is a compound comprising the group 4 to 6 metal coordinated with one or more carboxylate ligand, optionally one or more other ligands, and optionally one or more counterions.

7. The method of claim 6, wherein the carboxylate ligand is a monodentate carboxylate ligand of formula (I): ##STR00015## wherein R.sup.1 is a hydrogen atom or a monovalent organic radical.

8. The method of claim 6, wherein the carboxylate ligand is a bidentate carboxylate ligand of formula (II): ##STR00016## wherein R.sup.2 is a covalent bond or a bivalent organic radical.

9. The method of claim 6, wherein the carboxylate ligand is a tridentate carboxylate ligand of formula (III): ##STR00017## wherein R.sup.3 is a trivalent organic radical.

10. The method of claim 1, wherein the metal carboxylate is of formula (IV): ##STR00018## wherein M is the group 4 to 6 metal, U is a monodentate carboxylate ligand as defined above, V is a bidentate carboxylate ligand as defined above, W is a tridentate carboxylate ligand as defined above, u is 0 or more, v is 0 or more, w is 0 or more, x is 0 or more, y is 0 or more, and z is 0 or more, with the proviso that at least one of u, v, and w is 1 or more.

11. The method of claim 1, wherein the metal oxalate is niobium (V) hydrogen oxalate: ##STR00019##

12. The method of claim 1, wherein the metal carboxylate is an ammonium metal oxalate, and wherein the ammonium metal oxalate is ammonium niobium oxalate, which is: ##STR00020##

13. The method of claim 1, wherein comprising: reacting the metal carboxylate with hydrogen peroxide and citric acid to form a soluble peroxo-citrato-metal complex, and then reacting the peroxo-citrato-metal complex with the chalcogenide or the organochalcogenide, thereby producing the metal compound.

14. A metal compound made by the method of claim 1.

15. The metal compound of claim 14, consisting of niobium (Nb), sulfur(S), oxygen (O), nitrogen (N), and carbon (C).

16. The metal compound of claim 14, having a Raman spectrum comprising bands at about 84, about 152, about 218, about 246, about 438, and about 474 cm.sup.1; preferably having a Raman spectrum is as shown in FIG. 25.

17. A metal recovery electrode comprising the metal compound of claim 14 on a conducting support.

18. A method for manufacturing the metal recovery electrode of claim 17, the method comprising depositing the metal compound on the conducting support.

19. The method of claim 18, comprising electrodepositing the metal compound on the conducting support, wherein the electrodepositing comprises using the conducting support as a working electrode, using a counter-electrode, and using an aqueous suspension of particles of the metal compound as an electrolyte between the working electrode and the counter-electrode.

20. A method for the electrochemical recovery of a metal from a spent electrode, the method comprising the steps of: A) providing an electrochemical cell comprising the metal recovery electrode of claim 17 as a working electrode, the spent electrode as a counter-electrode, and an electrolyte between the working electrode and the counter-electrode, and B) applying a potential or a current between the working electrode and the counter-electrode to dissolve the metal from the spent electrode and electrodeposit dissolved atoms of the metal on the metal recovery electrode, thereby recovering the metal and forming a composite electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0122] In the appended drawings:

[0123] FIG. 1 illustrates the process for recycling and upcycling PGMs to produce a composite gas diffusion electrode.

[0124] FIG. 2 shows a scanning electron microscopy (SEM) image of the self-supported earth-abundant compound on carbon fiber paper as prepared in Example 1.

[0125] FIG. 3 shows the energy dispersive X-ray (EDX) spectrum of the earth-abundant electrode prepared in Example 1.

[0126] FIG. 4 shows the survey X-ray photon spectroscopy (XPS) spectrum of the earth-abundant electrode prepared in Example 1.

[0127] FIG. 5 shows the high-resolution XPS spectrum of the earth-abundant electrode prepared in Example 1, centered in the niobium (Nb) 3d region.

[0128] FIG. 6 shows the high-resolution XPS spectrum of the earth-abundant electrode prepared in Example 1, centered in the sulfur(S) 3d region.

[0129] FIG. 7 shows the high-resolution XPS spectrum of the earth-abundant electrode prepared in Example 1, centered in the oxygen (O) 1s region.

[0130] FIG. 8 shows the high-resolution XPS spectrum of the earth-abundant electrode prepared in Example 1, centered in the nitrogen (N) 1s region.

[0131] FIG. 9 shows the cyclic voltammograms (CV) for the progressive Pt dissolution from a planar electrode and the deposition to produce the Pt/earth-abundant electrode prepared in Example 2. Inset represents the typical CV curves of the earth-abundant electrode (1) and the Pt/earth-abundant electrode (2000). All measurements were recorded in 0.5M H.sub.2SO.sub.4 at a scan rate of 100 mV s.sup.1.

[0132] FIG. 10 shows the scanning electron microscopy (SEM) image of the Pt/earth-abundant electrode prepared in Example 2.

[0133] FIG. 11 shows the EDX spectrum of the composite Pt/earth-abundant electrode prepared in Example 2.

[0134] FIG. 12 shows the EDX mapping of platinum (Pt) in the Pt/earth-abundant electrode prepared in Example 2.

[0135] FIG. 13 shows the EDX mapping of Nb in the Pt/earth-abundant electrode prepared in Example 2.

[0136] FIG. 14 shows the EDX mapping of S in the Pt/earth-abundant electrode in Example 2.

[0137] FIG. 15 shows the EDX mapping of O in the Pt/earth-abundant electrode in Example 2.

[0138] FIG. 16 shows the EDX mapping of C in the Pt/earth-abundant electrode prepared in Example 2.

[0139] FIG. 17 shows the survey XPS spectrum of Pt/earth-abundant electrode prepared in Example 2.

[0140] FIG. 18 shows the high-resolution XPS spectrum of the Pt/earth-abundant electrode prepared in Example 2, centered in the Pt 4f region.

[0141] FIG. 19 shows the high-resolution XPS spectrum of the Pt/earth-abundant electrode prepared in Example 2, centered in the Nb 3d region.

[0142] FIG. 20 shows the high-resolution XPS spectrum of the Pt/earth-abundant electrode prepared in Example 2, centered in the S 2p region.

[0143] FIG. 21 shows the high-resolution XPS spectrum of the Pt/earth-abundant electrode prepared in Example 2, centered in the O 1s region.

[0144] FIG. 22 shows the performance towards the hydrogen evolution reaction (HER) of the Pt/earth-abundant composite electrode prepared in Example 2 as a function of the progressive cycling.

[0145] FIG. 23 shows the CVs for the progressive Pt dissolution from a Pt/C gas diffusion electrode and the deposition to produce the Pt/earth-abundant electrode prepared in Example 3. Inset represents the typical CV curves of the earth-abundant electrode (1) and the Pt/earth-abundant electrode (2000). All measurements were recorded in 0.5M H.sub.2SO.sub.4 at a scan rate of 100 mV s.sup.1.

[0146] FIG. 24 shows the performance towards the HER of the Pt/earth-abundant composite electrode prepared in Example 3 as a function of the progressive cycling.

[0147] FIG. 25 shows the full range Raman spectrum and zoom-in of the region corresponding to the earth-abundant compound prepared in Example 1.

[0148] FIG. 26 shows the Raman spectrum of the Pt/earth-abundant electrode prepared in Example 2.

DETAILED DESCRIPTION OF THE INVENTION

[0149] Turning now to the invention in more detail, in a first aspect of the invention, there is provided a metal compound made by the method described below. There is also provided a metal recovery electrode comprising this metal compound on a conducting support. An electrochemical method for the manufacturing of the metal recovery electrode is also provided.

[0150] In related aspects of the invention, uses of the metal compound and the metal recovery electrode are provided. Thus, in embodiments, the metal compound is for the electrochemical recovery of a metal from a spent electrode. Similarly, in embodiments, the metal recovery electrode is for the electrochemical recovery of a metal from a spent electrode.

[0151] In other related aspects of the invention, there is also provided the use of the metal compound for the electrochemical recovery of a metal from a spent electrode as well as the use of the metal recovery electrode for the electrochemical recovery of a metal from a spent electrode.

[0152] In yet another related aspect of the invention, there is provided a method for the electrochemical recovery of a metal from a spent electrode, the method comprising the steps of: [0153] A) providing an electrochemical cell comprising the metal recovery electrode as a working electrode, the spent electrode as a counter-electrode, and an electrolyte between the working electrode and the counter-electrode, and [0154] B) performing cyclic voltammetry on the metal recovery electrode, thereby dissolving the metal from the spent electrode and adsorbing dissolved atoms of the metal on the metal recovery electrode, thereby recovering the metal and forming a composite electrode.

[0155] This method allows the recycling of platinum group metals (PGMs) and other metals and their upcycling into useful composite electrodes.

[0156] The above combination of two electrochemical methods to 1) directly produce the metal recovery electrode (self-supported composite electrode using earth-abundant materials) and then to 2) recover a metal from a spent electrode allows reusing PGMs (and other metals) thus decreasing the amount of PGMs that is extracted from ores and PGMs sent to landfill, and favoring the controlled disassembly of the electrodes, incorporating a potential end-of-life design.

[0157] The present invention takes advantage of the fact that Group 5 electrocatalysts with terminated sulfur chalcogen ligands act as trapping sites for Pt deposition, thus allowing the electrochemical recovery of Pt nanoparticles and their reuse as composite electrodes. Hence, the present invention allows recycling and upcycling PGMs (and others) using a metal recovery electrode based on an earth-abundant compound obtained from a cost-efficient and low-environmental risk electrochemical method.

[0158] In preferred embodiments below, we describe the manufacture of a precursor colloidal suspension of the metal compound comprising a group 4 to 6 transition metal and chalcogen species, which are deposited onto a support by electrodeposition to make a metal recovery electrode. Cyclic voltammetry is subsequently employed to dissolve Pt nanoparticles from spent Pt-containing electrodes and the metal recovery electrode is used to facilitate the recovery of platinum nanoparticles by the trapping effect of the chalcogen species and to produce a composite electrode with remarkable performance towards the hydrogen evolution reaction in acidic media.

[0159] This present invention represents a sustainable approach associated with safer operating conditions than conventional pyrometallurgical and hydrometallurgical technologies.

the Metal Compound & its Method of Manufacture

[0160] The present invention provides a metal compound made by a method comprising: [0161] reacting a metal carboxylate, wherein the metal is a group 4 to 6 metal, [0162] with [0163] a chalcogenide or an organochalcogenide.

[0164] The invention also relates to a method of manufacture of a metal compound comprising [0165] reacting a metal carboxylate, wherein the metal is a group 4 to 6 metal, [0166] with [0167] a chalcogenide or an organochalcogenide.

[0168] Herein, a group 4 to 6 metal is a metal from group 4 to 6 of the periodic table according to the modern IUPAC notation. Preferred group 4 to 6 metals include Ti, Zr, Nb, Ta, Hf, Mo, and W. A most preferred group 4 to 6 metal is niobium (Nb).

[0169] Herein, a metal carboxylate is a compound comprising the group 4 to 6 metal coordinated with one or more carboxylate ligand, optionally one or more other ligands, and optionally one or more counterions.

[0170] The carboxylate ligand can be a monodentate carboxylate ligand, a bidentate carboxylate ligand, or a tridentate carboxylate ligand.

[0171] The monodentate carboxylate ligand can be of formula (I):

##STR00008##

wherein R.sup.1 is a hydrogen atom or a monovalent organic radical. Note that * represents the point of attachment of the group 4 to 6 metal.

[0172] In preferred embodiments, R.sup.1 is a hydrogen atom, R.sup.11, O(CO)R.sup.12, (CO)OR.sup.12, (CO)R.sup.12, OR.sup.12, wherein: [0173] R.sup.11 is alkyl, alkenyl, alkynyl, or alkenynyl (preferably alkyl), each of being unsubstituted or substituted with one or more of OH, COOH, and/or C(O)H (preferably OH and/or COOH), and [0174] R.sup.12 is a hydrogen atom, alkyl, alkenyl, alkynyl, or alkenynyl (preferably a hydrogen atom or alkyl), wherein the alkyl, alkenyl, alkynyl, or alkenynyl is unsubstituted or substituted with one or more of OH, COOH, and/or C(O)H (preferably OH and/or COOH).

[0175] In most preferred embodiments, R.sup.1 is: [0176] a hydrogen atom (formate ligand), [0177] COOH (oxalate monodentate ligand), [0178] CH(OH)CH(OH)COOH (tartrate monodentate ligand), or [0179] CH.sub.2C(OH)(COOH)CH.sub.2COOH (citrate monodentate ligand).

[0180] The bidentate carboxylate ligand can be of formula (II):

##STR00009##

wherein R.sup.2 is a covalent bond or a bivalent organic radical. Note that * represents the point of attachment of the group 4 to 6 metal.

[0181] In preferred embodiments, R.sup.2 is a covalent bond, R.sup.21, O(CO)R.sup.22, R.sup.22O(CO), (CO)OR.sup.22, R.sup.22(CO)O, (CO)R.sup.22, R.sup.22(CO), OR.sup.22, R.sup.22O, wherein: [0182] R.sup.21 is alkylene, alkenylene, alkynylene, or alkenynylene (preferably alkylene), each of which being unsubstituted or substituted with one or more of OH, COOH, and/or C(O)H (preferably OH and/or COOH), and [0183] R.sup.22 is a covalent bond or alkylene, alkenylene, alkynylene, or alkenynylene (preferably a covalent bond or alkylene), wherein the alkylene, alkenylene, alkynylene, or alkenynylene is unsubstituted or substituted with one or more of OH, COOH, and/or C(O)H (preferably OH and/or COOH).

[0184] In most preferred embodiments, R.sup.2 is [0185] a covalent bond (bidentate oxalate ligand) or [0186] alkylene (preferably propylene, more preferably n-propylene), said alkylene being unsubstituted or substituted as noted above; preferably substituted; more preferably substituted with OH and/or COOH.

[0187] Most preferably R.sup.2 is: [0188] CH(OH)CH(OH) (bidentate tartrate ligand), or [0189] CH.sub.2C(OH)(COOH)CH.sub.2 (bidentate citrate ligand).

[0190] The tridentate carboxylate ligand can be of formula (III):

##STR00010##

wherein R.sup.3 is a trivalent organic radical. Note that * represents the point of attachment of the group 4 to 6 metal.

[0191] In preferred embodiments, R.sup.3 is alkylidyne, alkenylidyne, alkynylidyne, or alkenynylidyne, wherein the alkylidyne, alkenylidyne, alkynylidyne, or alkenynylidyne is unsubstituted or substituted with one or more of OH, COOH, and/or C(O)H (preferably OH and/or COOH), and wherein the alkylidyne uninterrupted or interrupted by one or more of O, (CO), O(CO), (CO)O.

[0192] In preferred embodiments, R.sup.3 is alkylidyne. In most preferred embodiments, the alkylidyne is propylidyne, more preferably n-propylidyne).

[0193] In embodiments, the alkylidyne, alkenylidyne, alkynylidyne, or alkenynylidyne (preferably alkylidyne) is uninterrupted. In embodiments, the alkylidyne, alkenylidyne, alkynylidyne, or alkenynylidyne (preferably alkylidyne) is substituted as noted above; more preferably substituted with OH and/or COOH; yet more preferably substituted with OH.

[0194] Most preferably, R.sup.3 is

##STR00011##

(tridentate citrate ligand).

[0195] As noted above, the metal carboxylate optionally comprises one or more other ligands. Non-limiting examples of such other ligands include O, and OH.sub.2 (water). In preferred embodiments, the metal carboxylate comprises: [0196] one or more (preferably one) O, [0197] one or more (preferably two) OH.sub.2, or [0198] both one or more (preferably one)=O and one or more (preferably two) OH.sub.2.

[0199] In alternative preferred embodiments, the metal carboxylate comprises no other ligands.

[0200] As noted above, the metal carboxylate optionally comprises one or more counterions. Non-limiting examples of counterion include NH.sub.4.sup.+ (ammonium) as well as ions of alkaline metals and alkaline earth metals (i.e. groups 1 and 2 of the periodic table), such as sodium, potassium, calcium, and magnesium. Preferred counterions include NH.sub.4.sup.+.

[0201] In preferred embodiments, the metal carboxylate is of formula (IV):

##STR00012##

wherein [0202] M is the group 4 to 6 metal, [0203] U is a monodentate carboxylate ligand as defined above, [0204] V is a bidentate carboxylate ligand as defined above, [0205] W is a tridentate carboxylate ligand as defined above, [0206] u is 0 or more, [0207] v is 0 or more, [0208] w is 0 or more, [0209] x is 0 or more, [0210] y is 0 or more, and [0211] z is 0 or more,
with the proviso that at least one of u, v, and w is 1 or more.

[0212] In preferred embodiments, u is 1 or more and v=w=0; or v is 1 or more and u=w=0.

[0213] It will be apparent to the skilled person that the number and nature of the carboxylate ligand(s) and of the optional other ligands are selected according to the valency of the metal; and that the number and nature of the counterion(s) are selected such that the counterion(s) total charge ensures the neutrality of the metal carboxylate compound.

[0214] In more preferred embodiments, the group 4 to 6 metal is niobium, preferably wherein u=w=0, v is 1 or more (preferably 2), x is 1 or more (preferably 1), y is 1 or more (preferably 2), and/or (preferably and) z is 1; most preferably wherein [counterion].sub.z represents one counterion having a charge of +1, preferably NH.sub.4.sup.+.

[0215] In alternative preferred embodiments, the group 4 to 6 metal is niobium, preferably u is 1 or more (preferably 5), v=w=0, x is 0, y is 0, and/or (preferably and) z is 0.

[0216] Most preferred carboxylate ligands include monodentate oxalate ligand(s) and/or (preferably or) bidentate oxalate ligand(s).

[0217] In most preferred embodiments, the metal carboxylate is a metal oxalate or an ammonium metal oxalate, preferably an ammonium metal oxalate.

[0218] Herein, a metal oxalate is a metal carboxylate comprising one or more oxalate ligand (as the carboxylate ligand). In preferred embodiments, the metal oxalate comprises: [0219] one or more oxalate ligand as the carboxylate ligand (preferably the oxalate ligand is a monodentate oxalate ligand, i.e., u is 1 or more; and preferably v=w=0); [0220] no counterion (z is 0); and/or (preferably and) [0221] no other ligand (x=y=0).
A most preferred metal oxalate is niobium (V) hydrogen oxalate:

##STR00013##

[0222] Herein, an ammonium metal oxalate is a metal carboxylate comprising at least one monodentate oxalate ligand (as U, with u being 1 or more) or bidentate oxalate ligand (as V, with v being 1 or more) as the carboxylate ligand and one or more ammonium counterion (i.e., [counterion] is NH.sub.4.sup.+ and z is 1 or more). In preferred embodiments, the ammonium metal oxalate comprises: [0223] one or more bidentate oxalate ligands as the carboxylate ligand, i.e., V is a bidentate oxalate ligand and v is 1 or more (preferably 2), [0224] u=w=0, and [0225] one or more other ligand, preferably one or more O (x is 1 or more) and/or one or more water molecules (y is 1 or more), preferably both.
A most preferred ammonium metal oxalate is ammonium niobium oxalate, which is:

##STR00014##

[0226] In the invention, the metal carboxylate, such as the ammonium metal oxalate, may be in hydrated form or in non-hydrated form.

[0227] Herein, a chalcogen is a chemical element of group 16 of the periodic table according to the modern IUPAC notation and a chalcogenide is a compound comprising a chalcogen atom. Preferred chalcogenides comprise at least one S, Se, or Te atom. Most preferred chalcogenides comprise at least one S atom.

[0228] In preferred embodiments, an organochalcogenide is used.

[0229] Organochalcogenides are compounds comprising at least one chemical bond between a carbon atom of an organic group and a chalcogen atom. Preferred chalcogen in organochalcogenides include S, Se, and Te, more preferably S. Thus, the most preferred organochalcogenides are organosulfurs, such as thiophene, thiols, thiolanes, polysulfides, and thiazole.

[0230] Preferred organic groups in organochalcogenides include amino, carboxylate, carbonyl, and alkyl. The most preferred organic groups for organochalcogenides are amino and carbonyl.

[0231] A most preferred organochalcogenide is thiourea.

[0232] In more preferred embodiments, the method comprises: [0233] reacting the metal carboxylate with hydrogen peroxide and citric acid to form a soluble peroxo-citrato-metal complex, and [0234] then reacting the peroxo-citrato-metal complex with the chalcogenide or the organochalcogenide, thereby producing the metal compound.

[0235] This method of manufacture typically produces a colloidal suspension of particles of the metal compound.

[0236] In embodiments, the metal compound comprises niobium (Nb), sulfur(S), oxygen (O), nitrogen (N), and carbon (C).

[0237] In embodiments, the metal compound consists of niobium (Nb), sulfur(S), oxygen (O), nitrogen (N), and carbon (C).

[0238] In embodiments, the metal compound has a Raman spectrum comprising bands at about 84, about 152, about 218, about 246, about 438, and about 474 cm.sup.1. In embodiments, the Raman spectrum is as shown in FIG. 25.

[0239] In embodiments, the metal compound can be supported on a support. When the support is conducting, the electrode of the invention is obtained.

the Metal Recovery Electrode & its Method of Manufacture

[0240] As noted previously, the metal recovery electrode comprises the above metal compound on a conducting support.

[0241] The support can be any conducting support. Non limiting examples of support include [0242] carbon-based supports, such as carbon-fiber paper, carbon cloth, carbon foams, and carbon felt; [0243] carbon materials, such as: [0244] carbon black, [0245] porous carbon materials, fullerenes, carbon nanotubes, carbon fibers, carbon filaments, carbon xerogel, carbon aerogel, nanocage carbons, carbon nanohorns, carbon nano-onions, carbon nano-capsules, and their graphitic forms, [0246] graphene-type materials, such as monolayer graphene, few layers graphene materials, reduced graphene oxide, and graphene oxide, [0247] heteroatom-doped carbon materials and heteroatom-doped graphene-type materials, wherein the heteroatom is preferably N, S, or P, and [0248] carbon nitride and graphitic carbon nitride; and [0249] meshes, foams, felts and porous transport layers from sintered nanoparticles of: [0250] one or more of Cu, Zn, Sb, Ag, Au, Pt, and Ru [0251] transition metal carbides, wherein the transition metal is preferably Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, or Fe, [0252] transition metal nitrides, wherein the transition metal is preferably Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Mn, Ni, Co, Fe, Cu; and [0253] conductive transition metal oxides, such as RuO.sub.2 and IrO.sub.2.

[0254] In preferred embodiments, the conducting support is carbon fiber paper.

[0255] The metal compound can be deposited on the conducting support using standard deposition methods.

[0256] In preferred embodiments, the metal recovery electrode is made by electrodepositing the metal compound on the conducting support. The present invention thus also provides a method of manufacturing the electrode comprising: electrodepositing the metal compound on the conducting support.

[0257] In embodiments, the electrodepositing comprises using the conducting support as a working electrode, using a counter-electrode, and using an aqueous suspension of particles of the metal compound as an electrolyte between the working electrode and the counter-electrode.

[0258] Preferred counter-electrode includes carbon rod, carbon fiber paper, and graphite plate. A most preferred counter-electrode is carbon fiber paper.

[0259] A reference electrode, such as Ag/AgCl, can also be used for the electrodeposition.

Uses and Method of Use of the Metal Compound and the Metal Recovery Electrode

[0260] As noted above, there is also provided the use of the metal compound for the electrochemical recovery of a metal from a spent electrode as well as the use of the metal recovery electrode for the electrochemical recovery of a metal from a spent electrode. Also, there is provided a method for the electrochemical recovery of a metal from a spent electrode, the method comprising the steps of: [0261] a) providing an electrochemical cell comprising the metal recovery electrode as a working electrode, the spent electrode as a counter-electrode, and an electrolyte between the working electrode and the counter-electrode, and [0262] b) applying a potential or a current between the working electrode and the counter-electrode to dissolve the metal from the spent electrode and electrodeposit dissolved atoms of the metal on the working electrode, thereby recovering the metal and forming a composite electrode.

[0263] Indeed, the abundant chalcogen-containing sites (e.g., sulfur-containing sites) in the metal recovery electrode can trap the metal to be recovered.

[0264] A reference electrode, such as Ag/AgCl, can also be used for step b).

[0265] The metal to be recovered from the spent electrode can be any noble metal, such as Pt, Pd, Ir, Au, and Ag, as well as Ni and Cu. Indeed, these have an affinity to binding organosulfur compounds, organochalcogenides, and sulfides. In preferred embodiments, the metal to be recovered is Pt.

[0266] The spent electrode can be for example end-of-life electrodes from membrane electrode assemblies of proton exchange membrane fuel cells, from electrolyzers, from metal-air batteries, from reversible fuel cells, from water splitting devices, or from solar energy conversion devices.

[0267] In embodiments, the method further comprises the step c) of using the composite electrode as a gas diffusion electrode, preferably for hydrogen evolution.

Definitions

[0268] The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

[0269] The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to) unless otherwise noted. In contrast, the phrase consisting of excludes any unspecified element, step, ingredient, or the like. The phrase consisting essentially of limits the scope to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the invention.

[0270] Herein, the term radical means a subunit of a larger molecule. A monovalent radical is attached to this larger molecule via a single bond, a bivalent radical is attached to the larger molecule via two bonds, and a trivalent radical is attached to the larger molecule via three bonds.

[0271] Herein, the terms alkyl, alkylene, alkylidyne and their derivatives have their ordinary meaning in the art. For more certainty, herein:

TABLE-US-00001 Term Definition Saturated aliphatic hydrocarbons alkane aliphatic hydrocarbon of general formula C.sub.nH.sub.2n+2 alkyl monovalent alkane radical of general formula C.sub.nH.sub.2n+1 alkylene bivalent alkane radical of general formula C.sub.nH.sub.2n (also called alkanediyl) alkylidyne trivalent alkane radical of general formula C.sub.nH.sub.2n1 Aliphatic hydrocarbons with double bond(s) alkene aliphatic hydrocarbon, similar to an alkane but comprising at least one double bond alkenyl monovalent alkene radical, similar to an alkyl but comprising at least one double bond alkenylene bivalent alkene radical, similar to an alkylene but comprising at least one double bond alkenylidyne trivalent alkene radical, similar to an alkylidyne but comprising at least one double bond Aliphatic hydrocarbons with triple bond(s) alkyne aliphatic hydrocarbon, similar to an alkane but comprising at least one triple bond alkynyl monovalent alkyne radical, similar to an alkyl but comprising at least one triple bond alkynylene bivalent alkyne radical, similar to an alkylene but comprising at least one triple bond alkynylidyne trivalent alkyne radical, similar to an alkylidyne but comprising at least one triple bond Aliphatic hydrocarbons with double and triple bonds alkenyne aliphatic hydrocarbon, similar to an alkane but comprising at least one double bond and at least one triple bond alkenynyl monovalent alkenyne radical, similar to an alkyl but comprising at least one double bond and at least one triple bond alkenynylene bivalent alkenyne radical, similar to an alkylene but comprising at least one double bond and at least one triple bond alkenynylidyne trivalent alkenyne radical, similar to an alkylidyne but comprising at least one double bond and at least one triple bond

[0272] It is to be noted that, unless otherwise specified, the hydrocarbon chains of the above groups can be linear or branched. Further, unless otherwise specified, these groups can contain between 1 and 18 carbon atoms, more specifically between 1 and 12 carbon atoms, between 1 and 6 carbon atoms, between 1 and 3 carbon atoms.

[0273] Herein, a group interrupted with one or more A, B, and/or C means that one or more A, B, and/or C groups are inserted between pairs adjacent carbon atoms of the group (for example, a butylene group (CH.sub.2CH.sub.2CH.sub.2CH.sub.2) interrupted by O may be CH.sub.2CH.sub.2OCH.sub.2CH.sub.2. Preferably, only one of A, B or C is inserted between any given pair of adjacent carbon atoms. However, when more than one pairs of adjacent carbon atoms are thus interrupted, the A, B, and C groups do not need to be identical: for example, one hydrogen atom may be replaced by A, while another may be replaced by B (for example a butylene group (CH.sub.2CH.sub.2CH.sub.2CH.sub.2) interrupted by O and NR may be CH.sub.2NRCH.sub.2OCH.sub.2CH.sub.2.

[0274] Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All subsets of values within the ranges are also incorporated into the specification as if they were individually recited herein.

[0275] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

[0276] The groups of the periodic table are identified herein using the modern IUPAC convention (which uses Arabic numerals from 1 to 18).

[0277] The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed.

[0278] No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0279] Herein, the term about has its ordinary meaning. In embodiments, it may mean plus or minus 10% or plus or minus 5% of the numerical value qualified.

[0280] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0281] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0282] The present invention is illustrated in further details by the following non-limiting examples.

Example 1Preparation and Characterization of a Self-supported Earth Abundant Catalyst and Electrode

[0283] As included in FIG. 1, a precursor solution was prepared in a glass reactor coupled with a degassing valve. 2.39 g ammonium niobium oxalate (CBMM, 23.1% Nb) were mixed with 17.6 mL hydrogen peroxide (H.sub.2O.sub.2, Thermo Scientific, 30%), and stirred for 3 min before adding 1.04 g of citric acid (Fisher Scientific, 99.6%). The bright yellow solution was kept in an oil bath at 50 C. and magnetically stirred for 20 h; the temperature of the solution was maintained at 35-40 C. Subsequently, the solution was removed from the oil bath, and 1.04 g thiourea (Thermo Scientific, 99%) were added slowly to control the highly exothermic reaction; the solution temperature increased to 70-80 C. The glass reactor was kept in the oil bath at 50 C., and the lighter yellow solution was stirred for another hour. Finally, the solution was cooled down to 35 C. and stirred and bubbled with nitrogen gas while 0.72 g thiourea were further added and stirred for 30 min, resulting in a yellow/whiteish colloidal suspension.

[0284] The earth-abundant compound was electrodeposited into carbon fiber paper (CFP, Spectracarb 2050A-0850), previously cut (3015 mm.sup.2), ultrasonically cleaned in acetone for 15 min, and oxidized in a furnace at 500 C. for 2 hours. The electrodeposition was performed in a three-electrode cell configuration; CFP was used as the working electrode, a saturated Ag/AgCl as the reference electrode, and a Pt plate as the counter-electrode. The precursor colloidal suspension (8 mL) was mixed with deionized water to reach a 20 mL volume and magnetically stirred and bubbled with nitrogen during electrodeposition. A Teflon/Pt contact electrode was used to hold the CFP substrate and maintained at 1 cm below the solution level. A 20 mA cm.sup.2 was applied in galvanostatic mode for 1 hour. Then, the sample was washed with distilled water and dried under ambient conditions before using it for the PGM recovery.

Characterization by SEM/EDS

[0285] Scanning electron microscopy (SEM) was carried out using a Tescan Vega3 LMH scanning electron microscope equipped with a Quantax energy dispersive X-ray (EDX) detector.

[0286] The morphology of the self-supported earth-abundant compound was characterized by SEM, shown in FIG. 2. The electrodeposition allows for the homogeneous growth of the earth-abundant compound onto the CFP with morphologies that can be further tuned by adjusting the electrodeposition parameters. FIG. 3 exhibits the EDS spectrum which confirms the presence of the constituent elements, including niobium (Nb), sulfur(S), oxygen (O), nitrogen (N), and carbon (C). No other elements were found.

Characterization by X-Ray Photoelectron Spectroscopy

[0287] X-ray photoelectron spectroscopy (XPS) was performed in a VG Escalab 220i-XL equipped with a twin anode X-ray source. All the spectra were corrected to give the adventitious C 1s spectral component a binding energy of 284.8 eV. XPS analysis was performed to obtain information about the surface chemical composition of the earth-abundant compound electrode. The survey spectrum in FIG. 4 confirms the presence of previously identified elements (Nb, S, O, N, and C). FIG. 5 exhibits the high-resolution Nb 3d spectrum where the two components at 208.4 (Nb 3d.sub.5/2) and 211.1 eV (Nb 3d.sub.3/2) are related to Nb(V)..sup.27 The S 2p region is shown in FIG. 6 where the peaks located at 164.6 and 166.0 eV are related to heterocyclic sulfur.sup.28, 29 and the peaks at 169.3, and 170.4 eV are related to the oxidized sulfur species. FIG. 7 shows the O 1s peak, which was deconvoluted into two components at 532.7 eV related to the oxidized sulfur and carbon species (CO, CO).sup.29 and another at 534.5 eV chemisorbed water. Lastly, FIG. 8 shows N 1s core-level spectrum with two components at 401.1 and 402.6 eV related to quaternary and oxidized N species, respectively.

Characterization by Raman Spectroscopy

[0288] The Raman spectrum included in FIG. 25 shows a zoom in highlighting the Raman bands corresponding to the earth-abundant compound at 84 cm.sup.1 assigned to the S inter-ring stretching, the band at 152 cm.sup.1 attributed to the NbNb vibrational mode, along with the characteristic band of the NbONb bending modes.sup.2.10. Moreover, the bands at 246, 438 and 474 cm.sup.1, correspond to the NbS, S-interring (and SO.sub.4) and the CSC stretching modes, respectively..sup.2.4, 2.11, 2.12 The bands around 1350 and 1585 cm.sup.1 are attributed to D and G bands of the carbon support.

Example 2Electrochemical Recycling/Upcycling of Platinum from a Planar Electrode Using the Electrode of Example 1

Progressive Platinum Loading

[0289] The PGM recovery from a planar electrode was conducted in a three-electrode cell, using the above-mentioned self-supported earth-abundant compound/CFP as working electrode, a saturated Ag/AgCl as reference electrode, and a Pt plate as the counter-electrode. The surface of the flat Pt counter electrode was reduced/oxidized by performing cyclic voltammetry on the earth-abundant electrode produced in Example 1 in 0.5 M H.sub.2SO.sub.4, using a Solartron SI 1287 Potentiostat/Galvanostat, in the potential window range of 0.7 V to 1 V. The working electrode was cycled 2 000 times using a scan rate of 100 mV s.sup.1 as included in FIG. 9. During the first cycle towards the cathodic direction in the working electrode, the surface of the Pt counter electrode is oxidized. Subsequently, this Pt oxide layer is reduced and exposes the Pt metal surface. The exposed Pt metal dissolves into the H.sub.2SO.sub.4 electrolyte. The dissolved Pt species migrate to the working electrode, where the earth-abundant catalyst traps them due to its abundant sulfur-containing sites. The newly upcycled Pt particles can be observed in the CV included in the inset (FIG. 9), which compares the initial earth-abundant electrode with no redox peaks and the final composite electrode comprising the typical Pt redox processes in this potential window range.

Characterization by SEM/EDS

[0290] FIG. 10 exhibits a low magnification SEM image showing the Pt/earth-abundant catalyst homogenously deposited onto the carbon fibers from the substrate. The EDS spectrum shown in FIG. 11 confirms the presence of all the elements including Pt, Nb, S, O, and C. The EDS mapping included in FIGS. 12, 13, 14, 15 and 16 corroborates the homogeneous dispersion of all elements, i.e., Pt, Nb, S, and O, onto the C, respectively, from the CFP substrate.

Characterization by XPS

[0291] The survey spectrum in FIG. 17 confirms the above-identified elements (Nb, S, O, N, and C). The high-resolution Pt 4f spectrum shown in FIG. 18 consists of a pair of doublets, located at 71.5 and 74.9 eV, assigned to the metallic Pt species..sup.30 The Nb 3d spectrum in FIG. 19 displays the previously identified components at the same position, i.e., 208.4 and 211.1 eV related to Nb(V). The S 2p spectrum shown in FIG. 20 exhibits a shift of two components to lower binding energies, where the 162.8 and 164.0 eV peaks are associated with the thiolate species bound to the metal surface.sup.31, 32 and the peaks at 169.1 and 170.2 eV are related to the oxidized sulfur species. As previously found, the O 1s in FIG. 21 displays two components at 532.4 eV and 534.1 eV, related to the oxidized sulfur and carbon species (CO, CO) for the former and to the chemisorbed water for the latter. The absence of N in the composite electrode indicates that the occurrence in the as-prepared earth-abundant catalyst was due to impurities of the thiourea precursor.

Characterization by Raman Spectroscopy

[0292] The spectrum displayed in FIG. 26 shows the same Raman bands attributed to the earth-abundant compound, the NbNb and NbONb vibrational modes located at 152 and 222 cm 1, respectively. Additionally, the Raman active bands assigned to the Pt in complexes at 117 cm.sup.1 and the ones related to the PtS bonding are located at 301, 350 and 470 cm.sup.1. Moreover, the bands at 641 and 1450 cm.sup.1 are attributed to the CSC and the CC (heterocyclic) stretching modes. The bands around 1350 and 1585 cm.sup.1 are related to D and G bands of the carbon support.

Performance of the Composite Electrode Towards the Hydrogen Evolution Reaction

[0293] The polarization curves included in FIG. 22 were obtained after each series of cyclic voltammograms (1, 500, 1000, 1500, and 2000). The curves reported correspond to the third linear scan sweep from 0.5 to 0.7V vs Ag/AgCl at a scan rate of 10 mV s.sup.1. The overpotential needed to achieve a benchmark cathodic current density of 10 mA cm 2 is reduced significantly from 272 mV (1.sup.st cycle) to 15 mV (2000.sup.th cycle), due to the increase of the Pt content in the resulting earth-abundant composite electrode.

Example 3Electrochemical Recycling/Upcycling of Platinum from a Gas Diffusion Electrode Using the Electrode of Example 1

[0294] The PGM recovery from a gas diffusion electrode was conducted in a three-electrode cell configuration. The self-supported earth-abundant catalyst/CFP was used as working electrode, a saturated Ag/AgCl as reference electrode, and a Pt/C gas diffusion electrode (Carbon cloth, 60 wt % Pt/C, 3 mg Pt/cm.sup.2) as counter-electrode. As previously described, cyclic voltammetry was performed on the earth-abundant electrode in 0.5 M H.sub.2SO.sub.4, using a Solartron SI 1287 Potentiostat/Galvanostat, in the potential window range of 0.7 V to 1 V. FIG. 23 displays the cycle voltammograms obtained at 1, 500, 1000, 1500 and 2000 cycles using a scan rate of 100 mV s.sup.1. The inset in this figure, compares the initial stage of the earth-abundant electrode with no redox peaks and the final state of the composite electrode comprising the typical Pt redox processes in this potential window range. As previously demonstrated and as included in FIG. 24, the progressive Pt loading in the earth-abundant electrode contributes to a remarkable decrease in the overpotential needed to drive the hydrogen evolution reaction, requiring an overpotential <30 mV to achieve a cathodic current density of 10 mA cm.sup.2. This remarkable performance indicates the feasibility of using a direct electrochemical approach to recycle and upcycle these critical materials and obtain a composite electrode including earth-abundant elements.

[0295] The scope of the claims should not be limited by the preferred embodiments set forth in the examples but should be given the broadest interpretation consistent with the description as a whole.

REFERENCES

[0296] The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety. These documents include, but are not limited to, the following: [0297] 1. Reck, B. K.; Graedel, T. E., Challenges in metal recycling. Science 2012, 337 (6095), 690-695. [0298] 2. Harper, G.; Sommerville, R.; Kendrick, E.; Driscoll, L.; Slater, P.; Stolkin, R.; Walton, A.; Christensen, P.; Heidrich, O.; Lambert, S., Recycling lithium-ion batteries from electric vehicles. nature 2019, 575 (7781), 75-86. [0299] 3. Mrozik, W.; Rajaeifar, M. A.; Heidrich, O.; Christensen, P., Environmental impacts, pollution sources and pathways of spent lithium-ion batteries. Energy & Environmental Science 2021, 14 (12), 6099-6121. [0300] 4. Koehler, J. Z., Ralf; Binder, Matthias; Baenisch, Volker; Lopez, Marco Process for recycling fuel cell components containing precious metals. 2008. [0301] 5. Paepke, M. Method for recycling membrane/electrode units of a fuel cell. 2015. [0302] 6. Mountain, B. W.; Wood, S. A., Solubility and transport of platinum-group elements in hydrothermal solutions: thermodynamic and physical chemical constraints. In Geo-platinum 87, Springer: 1988; pp 57-82. [0303] 7. Vincent, R. C., Raphael; Dubau, Laetitia, Duclos, Lucken, Svecova, Lenk, Thivel, Pierre-Xavier WO2018/138427A1 2018. [0304] 8. Granados-Fernndez, R.; Montiel, M. A.; Diaz-Abad, S.; Rodrigo, M. A.; Lobato, J., Platinum Recovery Techniques for a Circular Economy. Catalysts 2021, 11 (8), 937. [0305] 9. Andersen, S. M. S., Raghunandan Method for dissolving precious metals. 2019. [0306] 10. Eifert, A. B., Claudio Method for obtaining platinum and/or ruthenium. 2021. [0307] 11. Furuya, Y.; Mashio, T.; Ohma, A.; Tian, M.; Kaveh, F.; Beauchemin, D.; Jerkiewicz, G., Influence of electrolyte composition and pH on platinum electrochemical and/or chemical dissolution in aqueous acidic media. Acs Catalysis 2015, 5 (4), 2605-2614. [0308] 12. Chia, X.; Eng, A. Y. S.; Ambrosi, A.; Tan, S. M.; Pumera, M., Electrochemistry of nanostructured layered transition-metal dichalcogenides. Chemical reviews 2015, 115 (21), 11941-11966. [0309] 13. Yang, J.; Mohmad, A. R.; Wang, Y.; Fullon, R.; Song, X.; Zhao, F.; Bozkurt, I.; Augustin, M.; Santos, E. J.; Shin, H. S., Ultrahigh-current-density niobium disulfide catalysts for hydrogen evolution. Nature materials 2019, 18 (12), 1309-1314. [0310] 14. Liu, Y.; Wu, J.; Hackenberg, K. P.; Zhang, J.; Wang, Y. M.; Yang, Y.; Keyshar, K.; Gu, J.; Ogitsu, T.; Vajtai, R., Self-optimizing, highly surface-active layered metal dichalcogenide catalysts for hydrogen evolution. Nature Energy 2017, 2 (9), 1-7. [0311] 15. Zhang, J.; Wu, J.; Zou, X.; Hackenberg, K.; Zhou, W.; Chen, W.; Yuan, J.; Keyshar, K.; Gupta, G.; Mohite, A., Discovering superior basal plane active two-dimensional catalysts for hydrogen evolution. Materials Today 2019, 25, 28-34. [0312] 16. Nowak, I.; Ziolek, M., Niobium compounds: preparation, characterization, and application in heterogeneous catalysis. Chemical Reviews 1999, 99 (12), 3603-3624. [0313] 17. Bayot, D.; Tinant, B.; Devillers, M., Water-soluble niobium peroxo complexes as precursors for the preparation of Nb-based oxide catalysts. Catalysis today 2003, 78 (1-4), 439-447. [0314] 18. Rani, R. A.; Zoolfakar, A. S.; O'Mullane, A. P.; Austin, M. W.; Kalantar-Zadeh, K., Thin films and nanostructures of niobium pentoxide: fundamental properties, synthesis methods and applications. Journal of Materials Chemistry A 2014, 2 (38), 15683-15703. [0315] 19. Si, J.; Zheng, Q.; Chen, H.; Lei, C.; Suo, Y.; Yang, B.; Zhang, Z.; Li, Z.; Lei, L.; Hou, Y., Scalable production of few-layer niobium disulfide nanosheets via electrochemical exfoliation for energy-efficient hydrogen evolution reaction. ACS applied materials & interfaces 2019, 11 (14), 13205-13213. [0316] 20. Najafi, L.; Bellani, S.; Oropesa-Nuez, R.; Martn-Garca, B.; Prato, M.; Maznek, V.; Debellis, D.; Lauciello, S.; Brescia, R.; Sofer, Z., Niobium disulphide (NbS 2)-based (heterogeneous) electrocatalysts for an efficient hydrogen evolution reaction. Journal of Materials Chemistry A 2019, 7 (44), 25593-25608. [0317] 21. Jha, G.; Tran, T.; Qiao, S.; Ziegler, J. M.; Ogata, A. F.; Dai, S.; Xu, M.; Le Thai, M.; Chandran, G. T.; Pan, X., Electrophoretic deposition of mesoporous Niobium (V) oxide nanoscopic films. Chemistry of Materials 2018, 30 (18), 6549-6558. [0318] 22. RobertaLee, G., Studies on the electrochemical deposition of niobium oxide. Journal of Materials Chemistry 1996, 6 (2), 187-192. [0319] 23. Zhitomirsky, I., Electrolytic deposition of niobium oxide films. Materials Letters 1998, 35 (3-4), 188-193. [0320] 24. Saez Cabezas, C. A.; Miller, K.; Heo, S.; Dolocan, A.; LeBlanc, G.; Milliron, D. J., Direct Electrochemical Deposition of Transparent Metal Oxide Thin Films from Polyoxometalates. Chemistry of Materials 2020, 32 (11), 4600-4608. [0321] 25. Narendar, Y.; Messing, G. L., Synthesis, decomposition and crystallization characteristics of peroxo-citrato-niobium: an aqueous niobium precursor. Chemistry of materials 1997, 9 (2), 580-587. [0322] 26. Tang, K.; Wang, X.; Li, Q.; Yan, C., High Edge Selectivity of In Situ Electrochemical Pt Deposition on Edge-Rich Layered WS2 Nanosheets. Advanced Materials 2018, 30 (7), 1704779. [0323] 27. Koito, Y.; Rees, G. J.; Hanna, J. V.; Li, M. M.; Peng, Y. K.; Puchtler, T.; Taylor, R.; Wang, T.; Kobayashi, H.; Teixeira, I. F., Structure-Activity Correlations for Brnsted Acid, Lewis Acid, and Photocatalyzed Reactions of Exfoliated Crystalline Niobium Oxides. ChemCatChem 2017, 9 (1), 144-154. [0324] 28. Noh, J.; Ito, E.; Nakajima, K.; Kim, J.; Lee, H.; Hara, M., High-resolution STM and XPS studies of thiophene self-assembled monolayers on Au (111). The Journal of Physical Chemistry B 2002, 106 (29), 7139-7141. [0325] 29. Manceau, M.; Gaume, J.; Rivaton, A.; Gardette, J.-L.; Monier, G.; Bideux, L., Further insights into the photodegradation of poly (3-hexylthiophene) by means of X-ray photoelectron spectroscopy. Thin Solid Films 2010, 518 (23), 7113-7118. [0326] 30. Vovk, E. I.; Kalinkin, A. V.; Smirnov, M. Y.; Klembovskii, I. O.; Bukhtiyarov, V. I., XPS study of stability and reactivity of oxidized Pt nanoparticles supported on TiO2. The Journal of Physical Chemistry C 2017, 121 (32), 17297-17304. [0327] 31. Buckel, F.; Effenberger, F.; Yan, C.; Glzhuser, A.; Grunze, M., Influence of aromatic groups incorporated in long-chain alkanethiol self-assembled monolayers on gold. Advanced Materials 2000, 12 (12), 901-905. [0328] 32. Laiho, T.; Leiro, J.; Lukkari, J., XPS study of irradiation damage and different metal-sulfur bonds in dodecanethiol monolayers on gold and platinum surfaces. Applied surface science 2003, 212, 525-529. [0329] 2.1. L. Najafi, S. Bellani, R. Oropesa-Nuez, B. Martn-Garca, M. Prato, V. Maznek, D. Debellis, S. Lauciello, R. Brescia and Z. Sofer, Journal of Materials Chemistry A, 2019, 7, 25593-25608. [0330] 2.2. K. Tang, X. Wang, Q. Li and C. Yan, Advanced Materials, 2018, 30, 1704779. [0331] 2.3. V. K. Jain and L. Jain, Coordination Chemistry Reviews, 2005, 249, 3075-3197. [0332] 2.4. B. R. Moraes, N. S. Campos and C. M. Izumi, Vibrational Spectroscopy, 2018, 96, 137-142. [0333] 2.5. A. Singhal, V. K. Jain, B. Varghese and E. R. Tiekink, Inorganica chimica acta, 1999, 285, 190-196. [0334] 2.6. L. Najafi, S. Bellani, R. Oropesa-Nuez, R. Brescia, M. Prato, L. Pasquale, C. Demirci, F. Drago, B. Martn-Garca and J. Luxa, Small, 2020, 16, 2003372. [0335] 2.7. J. Cui and L. Zhang, Journal of hazardous materials, 2008, 158, 228-256. [0336] 2.8. J. Noh, E. Ito, K. Nakajima, J. Kim, H. Lee and M. Hara, The Journal of Physical Chemistry B, 2002, 106, 7139-7141. [0337] 2.9. M. Manceau, J. Gaume, A. Rivaton, J.-L. Gardette, G. Monier and L. Bideux, Thin Solid Films, 2010, 518, 7113-7118. [0338] 2.10. J. A. Oliveira, M. O. Reis, M. S. Pires, L. A. Ruotolo, T. C. Ramalho, C. R. Oliveira, L. C. Lacerda and F. G. Nogueira, Materials Chemistry and Physics, 2019, 228, 160-167. [0339] 2.11. M. Hangyo, K. Kisoda, T. Nishio, S. Nakashima, T. Terashima and N. Kojima, Physical Review B, 1994, 50, 12033. [0340] 2.12. R. L. Frost, J. T. Kloprogge and W. N. Martens, Journal of Raman Spectroscopy, 2004, 35, 28-35.