Platinum oxide modified ruthenium oxide and electrodes for the oxygen evolution reaction.

Abstract

The present invention relates to transition metal (M) oxide modified ruthenium oxide (where M=Pt, Rh, Pd, Ag and / or Au), in particular to platinum oxide modified ruthenium oxide catalyst for oxygen evolution electrodes in polymer electrolyte membrane (PEM) fuel cells, water electrolysis, renewable fuel cells (RFC) or various electrolysis applications.

Description

[Technical Field]

[0001] The present invention relates to ruthenium oxide modified with transition metal (M) oxides (where M=Pt, Rh, Pd, Ag and / or Au), in particular platinum oxide catalysts for oxygen evolution electrodes in polymer electrolyte membrane (PEM) fuel cells, water electrolysis, renewable fuel cells (RFC) or various electrolysis applications. The present invention further relates to a process for obtaining the catalyst composition, a catalyst composition obtainable by or obtained by said process, an electronic device comprising said catalyst composition, and a catalyst composition for use as a catalyst for the oxygen evolution reaction.

[0002] Hydrogen is a promising clean energy carrier that can be produced by various technologies. High-quality hydrogen can be produced by water electrolysis. As known to those skilled in the art, a water electrolysis device comprises at least one anode-containing half-cell in which the oxygen evolution reaction (OER) occurs and at least one cathode-containing half-cell in which the hydrogen evolution reaction (HER) occurs. When two or more cells are connected to each other, a stacked configuration is obtained. Thus, a water electrolysis device having a stacked configuration comprises at least two anode-containing half-cells and / or at least two cathode-containing half-cells.

[0003] Different types of water electrolysis devices are known.

[0004] PEM water electrolysis devices use a solid polymer electrolyte that is responsible for the transport of protons from the anode to the cathode and for the separation of product gases while electrically insulating the electrodes from each other.

[0005] Due to its complexity, the oxygen evolution reaction has a slow kinetics, which is why a significant overpotential is required on the anode side to produce oxygen at a reasonable rate. Typically, PEM water electrolyzers operate at a voltage of approximately 1.5-2 V. Because the pH is very acidic (PEM: pH < 2) and high overpotentials must be applied, the materials present on the anode side of a PEM water electrolyzer must be very corrosion resistant.

[0006] Typically, the anode of a water electrolyzer contains a catalyst for the oxygen evolution reaction (OER electrocatalyst). Suitable OER electrocatalysts are known to those skilled in the art and are described, for example, in M. Carmo et al., "A comprehensive review on PEM water electrolysis," International Journal of Hydrogen Energy, Vol. 38, 2013, pp. 4901-4934, and H. Dau et al., "The Mechanism of Water Oxidation: From Electrolysis via Homogeneous to Biological Catalysis," ChemCatChem, 2010, 2, pp. 724-761.

[0007] Iridium or ruthenium oxides are known to be efficient catalysts for the oxygen evolution reaction (EP 2608297 A1; Reier et al. Electrocatalytic Oxygen Evolution Reaction in Acidic Environments Reaction Mechanisms and Catalysts. Adv. Energy Mater. 2017, 7, 1601275.).

[0008] However, iridium is scarce and expensive, and ruthenium oxide, both alone and in the form of a Pt-Ru alloy, has poor stability. The limited availability of iridium presents a major obstacle to the deployment of PEM electrolysis technology. To expand the use of electrolyzers, anodes made from cheaper, more abundant materials are needed.

[0009] As an alternative to iridium catalysts, several studies have been carried out on platinum-metal oxides using +1 / +2 / +3 ions such as Li, Na, Mg, Ca, Zn, Cd, Co, Ni, Mn, Cu, Ag, Bi, In, and Ce, where the +1 / +2 ions fit perfectly into the bronze structure.

[0010] European Patent No. 3581682(A1) discloses a homogeneous platinum bronze M containing a metal element M. x We have disclosed electrolytic anodes containing Pt3O4, where the metal element M is selected from the group consisting of Mn, Co, Cu, Ag, Bi, and Ce. These anodes are inexpensive and have excellent life spans, making them good alternatives to Ir anodes. However, their activity is still lower than that of Ir anodes.

[0011] RDShannon et al., Inorg. Chem., 21, 3372 (1982) x A method for synthesizing Pt3O4 (M = Li, Na, Mg, Ca, Zn, Cd, Co, and Ni) is disclosed.

[0012] International Patent Application Publication No. 2018 / 110423A1 describes the preparation of M by mixing platinum oxide (PtO2) and metal nitrates in a 3:1 molar ratio. x The synthesis of Pt3O4 is described. The metal nitrates used were Co, Ce, Ca, Li, Na, Bi, Ag, Cu, Mn, and In.

[0013] Yim et al., International Journal of Hydrogen Energy 30 (2005) 1345, Pt and RuO x Mixed PtRuO by physically mixing them to obtain electrocatalysts of appropriate composition. x They describe a method for preparing the material. The inorganic Ru precursor was dissolved in deionized water, and the aqueous solution was dried at 110 °C for 12 h, followed by calcination in air at 400 °C for 5 h to form the oxide phase. However, this material performed poorly as a catalyst for the oxygen evolution reaction.

[0014] Kamitaka et al. Catalysts 2018, 8, 258 discloses Co-Pt bronze for electrocatalysis in acidic media.

[0015] In their paper, "Oxygen and hydrogen evolution reactions on Ru, RuO2, Ir, and IrO2 thin film electrodes in acidic and alkaline electrolytes: A comparative study on activity and stability," Cherevkov et al. compare the activity and stability of metal and oxide Ir and Ru materials for the acidic oxygen evolution reaction (Catalysis Today 262 (2016) 170-180). Cherevkov et al. conclude that RuO2 is comparable to conventional Ir and IrO2 catalysts in terms of activity for the oxygen reaction. In terms of durability, the Ru-containing catalysts are inferior to their Ir counterparts. Cherevkov et al. also found that the metals have dissolution rates that are two to three orders of magnitude higher than their respective oxides. The higher dissolution rates mean that the catalysts are less stable under the reaction conditions.

[0016] Yi et al. reported in their paper "Effect of Pt introduced on Ru-based electrocatalyst for oxygen evolution activity and stability" (Electrochemistry Communications 104 (2019) 106469) that Ru deposited on a carbon support 09 Pt 0.1 discloses a catalyst of O2 composition. This phase was found to have some exceptionally high OER activity and remarkable stability. This observation was explained in two ways. First, dissolution of Pt from the catalyst surface produces a Pt-poor surface, forming an amorphous, water-containing surface layer with unsaturated but highly active Ru sites. Second, the core of the catalyst is formed by the initial Ru 0.9 Pt 0.1The catalyst consists of O2 and remains unchanged, which is catalytically inactive, but provides the necessary stability for a poor surface layer of amorphous, hydrous Pt. Although this catalyst shows some notable activity, the activity comes from the initial loss of expensive Pt from the catalyst surface, which is economically unattractive. The loss of precious metal is further compounded by the applied preparation route. Yi et al. 0.9 Pt 0.1 The alloy has been synthesized and a high-temperature calcination process has been used to convert this material to the binary oxide. However, as XRD analysis shows, the conversion is not quantitative, and the presence of metallic Ru may result in additional precious metal loss due to the metal's inherently higher dissolution rate. Furthermore, relying on a dissolution process to achieve the desired activity makes long-term stability in commercially relevant electrolytic cell systems difficult to achieve.

[0017] ASArico et al., "Electrochemical analysis of high temperature methanol electro-oxidation at Pt-decorated Ru catalysts" (Journal of Electroanalytical Chemistry 576 (2005) pp. 161-169) reported that in a direct methanol fuel cell at high temperatures, the electro-oxidation of 0.1 mg / cm2 in situ was 2 This paper deals with the study of methanol electrooxidation over Pt-modified unsupported Ru catalysts with Pt loadings of .

[0018] Qing Yao et al., "A trace of Pt can significantly boost RuO2 for acidic water splitting" (Chinese Journal of Catalysis 43 (2022) pp. 1493-501), discloses the activation and stabilization of RuO2-based electrocatalysts for acidic water splitting with trace amounts of Pt. Experimental and theoretical analyses reveal that atomically dispersed Pt incorporated within the RuO2 lattice helps to increase the concentration of O vacancies, which effectively enhances their interaction with reaction intermediates and thus lowers the energy barrier for the formation of OOH*.

[0019] The objective of the present invention is to provide a composition that is neither based on Ir nor on the inherently inert binary RuPt oxide phase. Furthermore, the composition should not rely on the surface dissolution of Pt to obtain the required activity increase. The objective of the present invention is to identify the stabilizing effect of the highly active RuO2 structure without changing the bulk morphology and composition of this bulk material.

[0020] The catalyst composition of the present invention comprises ruthenium oxide, RuO2, and particles containing a RuO2 lattice structure, the RuO2 particles having at least one transition metal (M) oxide deposited on the particle surface, where M=Pt, Rh, Pd, Ag and / or Au, and the transition metal (M) oxide is present in the RuO2 phase at less than 1 wt. %, calculated as the element M, relative to the total mass of the catalyst composition.

[0021] In contrast to other platinum-ruthenium oxide catalysts, the Ru oxide phase itself does not contain appreciable amounts of transition metal (M) oxide, preferably platinum. Preferably, the transition metal (M) oxide, calculated as the element M, is present in the RuO2 oxide at less than 0.75 wt. %, more preferably less than 0.5 wt. %, based on the total mass of the catalyst composition. Thus, the transition metal (M) oxide, calculated as the element M, may be present in the RuO2 oxide at 0 to less than 1 wt. %, preferably 0 to less than 0.75 wt. %, more preferably 0 to 0.5 wt. %, based on the total mass of the catalyst composition.

[0022] In contrast to other platinum ruthenium oxide catalysts, the catalyst composition comprises less than 5 wt. % of elemental transition metal (M), preferably platinum, based on the total mass of the catalyst, preferably less than 2 wt. %, more preferably less than 1 wt. %, more preferably less than 0.5 wt. %. Thus, elemental transition metal (M), preferably platinum, may be present in the RuO2 oxide at 0-5 wt. %, preferably less than 0-2 wt. %, more preferably 0-1 wt. %, more preferably 0-0.5 wt. %, based on the total mass of the catalyst composition.

[0023] The transition metal (M) oxide is preferably platinum, rhodium, palladium, silver and / or gold, more preferably platinum, palladium and / or rhodium, even more preferably platinum.

[0024] The elemental transition metal (M) is preferably platinum, rhodium, palladium, silver and / or gold, more preferably platinum, palladium and / or rhodium, even more preferably platinum.

[0025] The average layer thickness of the transition metal (M) oxide coating, preferably the platinum coating, is in the range of 1 nm to 5 nm, preferably 1 nm to 3 nm. x has been found to be finely distributed at the grain boundaries / surfaces of Ru oxide particles. The average layer thickness preferably relates to the median layer thickness. The coating thickness is preferably determined using transmission electron microscopy (TEM), since TEM provides a means for quantitatively and directly measuring the oxide thickness. TEM is preferably performed using a probe-corrected Themis Z 3.1 instrument (Thermo-Fisher, Waltham, USA) in various acquisition modes, such as high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), integrated differential phase contrast (iDPC)-STEM, bright-field TEM, and electron diffraction.

[0026] Preferably, the crystallite size of the RuO2 phase is in the range of 2 nm to 60 nm, more preferably in the range of 10 nm to 50 nm, and even more preferably in the range of 20 nm to 40 nm, as measured by XRD.

[0027] The transition metal oxide crystalline structure cannot be detected by XRD. If a Pt oxide crystalline structure is formed in trace amounts, the proportion of this platinum oxide phase is less than 0.5 wt. %, preferably less than 0.25 wt. %, more preferably less than 0.1 wt. %, relative to the total mass of the catalyst composition. Preferably, the transition metal (M) oxide, preferably Pt oxide, phase does not produce diffraction lines that can be attributed to it.

[0028] Preferably, all particles of the RuO2 phase have a particle size of less than 200 nm, preferably less than 150, more preferably less than 100, as measured by TEM particle size analysis.

[0029] The particle size of the RuO2 phase is preferably 5 to 150 nm, more preferably 10 to 80 nm on average, as characterized by TEM measurement. The shape of the particles is preferably spherical.

[0030] The deposition of transition metal oxide, preferably Pt oxide, on RuO can be carried out using any preparation technique known to those skilled in the art. Suitable preparation methods can be, for example, solution drop impregnation, atomic layer deposition, or chemical vapor deposition.

[0031] Another deposition method includes (a) mixing predetermined amounts of Pt oxide and Ru precursor, (b) reacting the raw material mixture in a solid state, and (c) removing by-products from the resulting reaction mixture. In this deposition process, it is preferable to keep the sodium content below 500 ppm.

[0032] The present invention provides a catalyst composition comprising ruthenium oxide, RuO2, and particles containing a RuO2 lattice structure, wherein the RuO2 particles have a transition metal (M) oxide deposited on the particle surface, where M=Pt, Rh, Pd, Ag, and / or Au; transition metal (M) oxide is present in the RuO phase in an amount of less than 1 wt. %, calculated as element M, relative to the total mass of the catalyst composition; There is further provided a catalyst composition, wherein the catalyst composition comprises less than 1 wt. % of elemental transition metal (M) based on the total mass of the catalyst.

[0033] The present invention also relates to a process for obtaining a catalyst composition, the composition comprising ruthenium oxide, RuO2, and particles containing a RuO2 lattice structure, the RuO2 particles having a transition metal (M) oxide deposited on the particle surface, where M=Pt, Rh, Pd, Ag and / or Au; transition metal (M) oxide is present in the RuO phase in an amount of less than 1 wt. %, calculated as element M, relative to the total mass of the catalyst composition; The process is (a) mixing a predetermined amount of Pt oxide and Ru precursor; (b) subjecting the raw material mixture to a solid-state reaction under predetermined conditions; (c) removing by-products from the resulting reaction product.

[0034] The present invention further provides a catalyst composition obtainable or obtained by the above-described process.

[0035] Preferably, the catalyst composition comprises less than 1% by weight, preferably 0 to less than 1% by weight, more preferably 0 to 0.5% by weight of elemental transition metal (M) relative to the total mass of the catalyst composition.

[0036] This invention demonstrates that materials based on ruthenium oxide modified with platinum oxide exhibit surprisingly high catalytic activity for the oxygen evolution reaction and are highly stable under highly corrosive conditions. Ruthenium is 20 times more available than iridium. This also solves the iridium supply problem and enables large-scale PEM electrolysis installations.

[0037] Catalyst characterization The term "ruthenium oxide modified with a transition metal (M) oxide, preferably platinum oxide" means that the catalyst comprises ruthenium oxide particles having a transition metal (M) oxide, preferably platinum oxide, deposited on the particle surface.

[0038] Preferably, the transition metal (M) oxide covers at least 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90%, more preferably 100% of the particle surface of the ruthenium oxide particles, for example, completely covering the particle surface of the ruthenium oxide particles. Analysis of the particle surface is preferably performed using transmission electron microscopy (TEM). TEM is preferably performed using a probe-corrected Themis Z 3.1 instrument (Thermo-Fisher, Waltham, USA) in various acquisition modes, such as high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), integrated differential phase contrast (iDPC)-STEM, bright-field TEM, and electron diffraction.

[0039] Preferably, the total amount of transition metal (M) oxides, preferably platinum, in the catalyst composition is in the range of 1 to 20 wt%, more preferably 5 to 15 wt%, more preferably 8 to 12 wt%, based on the total mass of the catalyst. Preferably, the remaining amount up to 100 wt% is ruthenium and oxygen. Preferably, the total amount of ruthenium in the catalyst composition is in the range of 55 to 75 wt%, more preferably 60 to 70 wt%, more preferably 63 to 67 wt%, based on the total mass of the catalyst.

[0040] The catalyst composition of the present invention is used in an amount of 5 to 200 m 2 / g, preferably 20 to 150, more preferably 30 to 100m 2 / g BET surface area.

[0041] Support Bulk catalysts may have limited surface area for electrochemical activity. To increase the catalytically active surface area, the catalyst composition may also be supported on a suitable support material. The support material is preferably an inorganic oxide, carbide, or nitride material, such as antimony-doped tin oxide (ATO), titanium suboxides (TiO, TiO, TiO, and TiO), TiC, ZrC, HfC, TaC, TiN, ZrN, HfN, TaN, boron carbides containing additional elements such as boron oxycarbides, or boron silicon oxycarbides, and more preferably TiO, doped or undoped SnO.

[0042] The catalyst composition of the present invention can also be used as the support material itself or coated with additional catalytic material, for example, iridium.

[0043] Crystallite size can be determined by X-ray analysis. X-ray diffraction (XRD) measurements can be used to determine crystallite size (diameter) and crystal orientation. Preferably, crystallite size can be determined by powder diffractograms. Preferably, data can be collected on a Bruker AXS D8 Advance diffractometer using a copper anode operating at 40 kV and 40 mA, scanning from 2° to 80° (2θ) using a step size of 0.02° (2θ). Data can be analyzed using TOPAS 6. Crystallite size can be reported using the integral width method (LVol-IB) reported by TOPAS.

[0044] The chemical composition can be analyzed via atomic emission spectroscopy or using energy dispersive X-ray spectroscopy (EDXS). Preferably, the chemical composition can be analyzed using an integrated SuperX G2 Energy-Dispersive X-Ray Spectroscopy (EDXS) detector (Thermo-Fisher, Waltham, USA). EDXS can be preferably used to analyze the grain boundaries / surfaces of Ru particles.

[0045] Transmission electron microscopy (TEM) can be used to analyze particle surfaces. In particular, TEM images can be used to analyze the particle surfaces of Ru particles. TEM is preferably performed using a probe-corrected Themis Z 3.1 instrument (Thermo-Fisher, Waltham, USA) in various acquisition modes, such as high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), integrated differential phase contrast (iDPC)-STEM, bright-field TEM, and electron diffraction.

[0046] Determination of the coating thickness can also be done using TEM, as it provides a means of quantitatively measuring oxide thickness directly.

[0047] Furthermore, particle size can be determined by TEM particle size analysis. Preferably, particle size analysis can be performed using the FIJI software tool (Schindelin, J., Arganda-Carreras, I., Frise, E., Kaynig, V., Longair, M., Pietzsch, T., Cardona, A. (2012). Fiji: an open-source platform for biological-image analysis. Nature Methods, 9(7), 676-682. doi:10.1038 / nmeth.2019).

[0048] Diffraction patterns can be evaluated using Prodas software (Proscope, Gangelt, Germany, version: 1.4).

[0049] advantage In contrast to the prior art, the described invention demonstrates a platinum oxide-modified ruthenium oxide catalytic material with surprisingly high activity and stability (much higher than the individual binary oxides) for the electrochemical oxygen evolution reaction under acidic conditions. The invention solves the problem of limited Ir supply by providing an alternative based on oxides of Ru and Pt, elements with significantly higher availability. In contrast to other reported Ru-containing materials, higher stability is achieved. Stability is achieved by depositing platinum oxide on the surface of RuO particles, rather than by removing platinum from the surface of Ru-containing particles.

[0050] The present invention is further illustrated by the following set of embodiments and combinations of embodiments obtained from the indicated dependencies and reverse references. In particular, in each case where a range of embodiments is mentioned, for example, in the context of a term such as "the catalyst composition according to any one of embodiments 1 to 4," it is noted that any embodiment within this range is expressly disclosed to a person skilled in the art, that is, this expression of the term is understood by a person skilled in the art to be synonymous with "the catalyst composition according to any one of embodiments 1, 2, 3, and 4." Furthermore, it is clearly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, thereby suitably supporting the claims of the present invention, but does not represent them.

[0051] Embodiment 1: 1. A catalyst composition comprising ruthenium oxide, RuO2, and particles containing a RuO2 lattice structure, wherein the RuO2 particles have at least one transition metal (M) oxide deposited on the particle surface, where M=Pt, Rh, Pd, Ag and / or Au, and the transition metal (M) oxide is present in the RuO2 phase at less than 1 wt. %, calculated as the element M, relative to the total mass of the catalyst composition.

[0052] Embodiment 2: 2. The catalyst composition of embodiment 1, wherein the proportion of the transition metal (M) oxide in the lattice structure is less than 0.5 wt. %, based on the total mass of the catalyst composition.

[0053] Embodiment 3: Catalyst composition according to embodiment 1 or 2, wherein the transition metal (M) oxide is present in the RuO2 phase of the RuO2 oxide at less than 0.75 wt. %, preferably less than 0.5 wt. %, calculated as element M, relative to the total mass of the catalyst composition; or wherein the transition metal (M) oxide is present in the RuO2 phase of the RuO2 oxide at 0 to less than 1 wt. %, preferably 0 to less than 0.75 wt. %, more preferably 0 to 0.5 wt. %, calculated as element M, relative to the total mass of the catalyst composition.

[0054] Embodiment 4: 4. The catalyst composition according to at least one of embodiments 1 to 3, comprising less than 5 wt. %, preferably less than 2 wt. %, more preferably less than 1 wt. %, more preferably less than 0.5 wt. % of elemental transition metal (M), preferably platinum, relative to the total mass of the catalyst; or 0-5 wt. % or less, preferably 0-2 wt. %, more preferably 0-1 wt. %, more preferably 0-1 wt. %, more preferably 0-0.5 wt. %, more preferably 0-0.5 wt. % of elemental transition metal (M), relative to the total mass of the catalyst composition.

[0055] Embodiment 5: the transition metal (M) oxide is platinum, rhodium, palladium, silver and / or gold, preferably platinum, palladium and / or rhodium, more preferably platinum; and / or 5. The catalyst composition according to at least one of embodiments 1 to 4, wherein the elemental transition metal (M) is platinum, rhodium, palladium, silver and / or gold, preferably platinum, palladium and / or rhodium, more preferably platinum.

[0056] Embodiment 6: 6. The catalyst composition according to at least one of embodiments 1 to 5, wherein the average layer thickness of the transition metal (M) oxide coating, preferably the platinum coating, is in the range of 1 nm to 5 nm, preferably 1 nm to 3 nm.

[0057] Embodiment 7: 7. The catalyst composition according to at least one of embodiments 1 to 6, wherein the crystallite size of the RuO2 phase is in the range of 2 nm to 60 nm, preferably in the range of 10 nm to 50 nm, more preferably in the range of 20 nm to 40 nm, as measured by XRD.

[0058] Embodiment 8: Catalyst composition according to at least one of embodiments 1 to 7, wherein if a Pt oxide crystalline structure is formed in trace amounts, the proportion of this platinum oxide phase is less than 0.5 wt. %, preferably less than 0.25 wt. %, more preferably less than 0.1 wt. %, relative to the total mass of the catalyst composition.

[0059] Embodiment 9: 9. The catalyst composition of at least one of embodiments 1 to 8, wherein all particles of the RuO2 phase have a particle size of less than 200 nm, preferably less than 150, more preferably less than 100, as measured by TEM particle size analysis.

[0060] Embodiment 10: 10. The catalyst composition according to at least one of embodiments 1 to 9, wherein the particle size of the RuO2 phase is on average 5 to 150 nm, preferably 10 to 80 nm.

[0061] Embodiment 11: the total amount of transition metal (M) oxides, preferably platinum, in the catalyst composition is in the range of 1 to 20% by weight, preferably 5 to 15% by weight, preferably 8 to 12% by weight, based on the total mass of the catalyst; and / or the remaining amount up to 100% by weight being ruthenium and oxygen, and / or 11. The catalyst composition according to at least one of embodiments 1 to 10, wherein the total amount of ruthenium in the catalyst composition is in the range of 55 to 75 wt. %, preferably 60 to 70 wt. %, more preferably 63 to 67 wt. %, based on the total mass of the catalyst.

[0062] Embodiment 12: 5~200m 2 / g, preferably 20 to 150, more preferably 30 to 100m 2 12. The catalyst composition of at least one of embodiments 1 to 11, having a BET surface area of ​​1 / g.

[0063] Embodiment 13: 13. The catalyst composition according to at least one of embodiments 1 to 12, supported on a support material, which is preferably an inorganic oxide, carbide, or nitride material.

[0064] Embodiment 14: 13. The catalyst composition according to at least one of embodiments 1 to 12, which is used as a support material itself, preferably coated with an additional catalytic material, preferably the additional catalytic material being iridium.

[0065] Embodiment 15: 15. The catalyst composition according to at least one of embodiments 1 to 14, comprising less than 2 wt. % of elemental transition metal (M), based on the total mass of the catalyst.

[0066] Embodiment 16: 16. The catalyst composition according to at least one of embodiments 1 to 15, wherein the average layer thickness of the transition metal (M) oxide coating is in the range of 1 nm to 5 nm.

[0067] Embodiment 17: 17. The catalyst composition of at least one of embodiments 1 to 16, wherein the crystallite size of the RuO2 phase ranges from 2 nm to 60 nm as measured by XRD.

[0068] Embodiment 18: 18. The catalyst composition of at least one of embodiments 1 to 17, wherein the particle size of the RuO2 phase is, on average, 5 to 150 nm, as characterized by TEM measurements.

[0069] Embodiment 19: 19. The catalyst composition of at least one of embodiments 1 to 18, comprising, based on the total mass of the catalyst, 1 to 20 wt. % of a transition metal (M) oxide, 55 to 75 wt. % of ruthenium, and the remaining amount of oxygen up to 100 wt. %.

[0070] Embodiment 20: 20. The catalyst composition according to at least one of embodiments 1 to 19, wherein the transition metal (M) oxide is platinum, rhodium and / or palladium, preferably the transition metal (M) oxide is platinum.

[0071] Embodiment 21: A catalyst composition comprising ruthenium oxide, RuO2, and particles containing a RuO2 lattice structure, wherein the RuO2 particles have a transition metal (M) oxide deposited on the particle surface, where M=Pt, Rh, Pd, Ag, and / or Au; transition metal (M) oxide is present in the RuO phase in an amount of less than 1 wt. %, calculated as element M, relative to the total mass of the catalyst composition; A catalyst composition, wherein the catalyst composition comprises less than 1 wt. % of elemental transition metal (M) based on the total mass of the catalyst.

[0072] Embodiment 22: 1. A process for obtaining a catalyst composition, the composition comprising ruthenium oxide, RuO2, and particles containing a RuO2 lattice structure, the RuO2 particles having a transition metal (M) oxide deposited on the particle surface, where M=Pt, Rh, Pd, Ag and / or Au; transition metal (M) oxide is present in the RuO phase in an amount of less than 1 wt. %, calculated as element M, relative to the total mass of the catalyst composition; The process is (a) mixing a predetermined amount of Pt oxide and Ru precursor; (b) subjecting the raw material mixture to a solid-state reaction; (c) removing by-products from the resulting reaction mixture.

[0073] Embodiment 23: 23. A catalyst composition obtainable or obtained by the process of embodiment 22.

[0074] Embodiment 24: 24. The catalyst composition of embodiment 23, comprising less than 1 wt. % of elemental transition metal (M), based on the total mass of the catalyst.

[0075] Embodiment 25: An electrochemical device comprising the catalyst composition according to any one of embodiments 1 to 24.

[0076] Embodiment 26: 26. Use of the catalyst composition according to any one of embodiments 1 to 25 as a catalyst for the oxygen evolution reaction. [Example]

[0077] Experimental procedure 1. Powder X-ray diffraction pattern The sample was homogenized in a mortar and spread flat on a sample holder. Data were collected on a Bruker AXS D8 Advance diffractometer using a copper anode operated at 40 kV and 40 mA. Scans were taken from 2° to 80° (2θ) using a step size of 0.02° (2θ). TOPAS 6 (1) The data was analyzed using the .Crystallite size was reported using the integral width method (LVol-IB) as reported by TOPAS.

[0078] literature (1)TOPAS 6 User Manual,2017,Bruker AXS GmbH.Karlsruhe,Germany 2. TEM Imaging and EDS Mapping Powder samples were dispersed in ethanol and applied to ultrathin carbon-coated grids by the drop-on grid method. The samples were imaged by transmission electron microscopy (TEM) using a probe-corrected Themis Z 3.1 instrument (Thermo-Fisher, Waltham, USA) in various acquisition modes, including high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), integrated differential phase contrast (iDPC)-STEM, bright-field TEM, and electron diffraction. Chemical composition was analyzed using an integrated SuperX G2 energy-dispersive X-ray spectroscopy (EDXS) detector (Thermo-Fisher, Waltham, USA). Data were analyzed using Velox 2.1x software (Thermo-Fisher, Waltham, USA). Particle size analysis was performed using the FIJI software tool (Schindelin, J., Arganda-Carreras, I., Frise, E., Kaynig, V., Longair, M., Pietzsch, T., Cardona, A. (2012). Fiji: an open-source platform for biological-image analysis. Nature Methods, 9(7), 676-682. doi:10.1038 / nmeth.2019). Diffraction patterns were evaluated using Prodas software (Proscope, Gangelt, Germany, version: 1.4).

[0079] 3. Electrochemical Measurements Experiments were performed in 0.5 M H2SO4 electrolyte at room temperature under an argon atmosphere. The catalysts were dispersed at 1 wt% in 10 / 1 H2O / IPA by sonication to obtain inks, which were then drop-cast onto gold electrodes. All catalysts were deposited as thin films to achieve the same total mass loading on the electrode. The electrodes were immersed in the electrolyte and activity was measured by linear sweep voltammetry over a potential range of 1.2–1.7 V vs. a reversible hydrogen electrode (RHE).

[0080] Preparation of Examples Samples of the present invention Ruthenium oxide modified with platinum oxide was prepared according to this method. Mixing was performed by dripping Ru(NO)NO solution (Lot No: 9002401825) from BASF Italia onto the PtO precursor with a Ru content of 18.8 wt.% by weight, completely covering / wetting the solid precursor. The atomic platinum to ruthenium ratio of this precursor was 3:1. PtO with a Na content of 500 ppm (Product No. 40402) from Sigma Aldrich was used.

[0081] The PtO2 impregnated with the Ru-containing solution was then ground to a fine powder, which was then dried and heat-treated using the following protocol: 1. Dry at 80°C for 12 hours 2. Heat at 5 K / min to 650°C. 3. Maintain at 650℃ for 6 hours 4. Cooling (10k / min)

[0082] After the heat treatment, the sample was treated with aqua regia at 80°C for 30 minutes. The aqua regia-treated sample was again dried at 80°C for 12 hours. The composition of the resulting material was confirmed by atomic emission spectroscopy. One sample, BRZ-12, was prepared according to this procedure. The sample contained 8.9% platinum by weight.

[0083] Comparative Example In the comparative example, samples containing PtO2 and RuO2 were prepared similarly to the inventive samples, except that platinum and ruthenium were dried and calcined separately. PtO2 (product number 206032) with a 1.6 wt% Na content from Sigma Aldrich was used as the Pt-containing material. Ru(NO)NO3 solution (lot number 9002401825) from BASF Italia was used as the inorganic Ru precursor with a Ru content of 18.8 wt% (used in the inventive examples). This Ru solution was dried and heat-treated separately in the absence of other metal precursors. The protocol was as follows: 1. Drying at 80°C (drying was performed in a vacuum drying oven and was extended until the solution became a dry powder) 2. Heat up to 650°C at 5K / min 3. Maintain at 650℃ for 6 hours 4. Cool (10k / min)

[0084] The individually heat-treated samples were then physically mixed and ground into a fine powder. A portion of this material was subjected to the same aqua regia treatment as described in the inventive examples. Two samples were prepared according to this procedure. Samples H2-PEM-192-2 and H2-PEM-194-2 contained 45% and 58% platinum by weight, respectively.

[0085] Comparison of Examples of the Invention and Comparative Examples TEM Figure 1 shows a TEM image and elemental mapping EDXS of a sample of the present invention. The TEM image reveals that the core of the particles consists of RuO2, with Pt only detectable on the particle surface. In addition, PtOx is found to be finely distributed at the grain boundaries / surface of the Ru particles.

[0086] Figure 2 shows a TEM image of the comparative sample after AR treatment. In contrast to the inventive sample, the comparative sample (H2-PEM-192, Figure 2) has both distinct Ru- and Pt-rich particles visible. The Pt particles of the comparative sample have a pronounced cubic shape.

[0087] XRD Figure 3 shows the diffraction pattern of the sample of the present invention. The reflections of the sample arise exclusively from the tetragonal RuO2 lattice. The crystallite size of RuO2 was calculated to be 25 nm. XRD measurements confirm that the material consists primarily of the RuO2 lattice structure.

[0088] Figure 4 shows the diffraction pattern of the comparative sample. The reflections of the sample arise from tetragonal RuO2, and the elemental Pt and Pt3O4 lattices can be detected. The crystallite sizes are 70 nm, 47 nm, and 39 nm, respectively.

[0089] Electrochemical activity of examples of the present invention and comparative examples a) Electrochemical cycling versus cycling stability A comparison of the inventive sample (BRZ4-AR) with RuO2 (Alfa Aesar) using the method described in a (see Figure 5) shows that while conventional RuO2 has very high initial activity, when the material is cycled over a large number of cycles between 1.2 and 1.7 V vs. RHE, activity is rapidly lost, disappearing completely after 30 cycles (see Figure 5a), whereas the inventive sample's activity is fully retained (see Figure 5b). Experiments were performed in 0.5 M H2SO4 electrolyte at room temperature under an argon atmosphere. The catalyst was dispersed at 1 wt% in 10:1 H2O / IPA by sonication to obtain an ink, which was then drop-cast onto a gold electrode. All catalysts were deposited as thin films to achieve the same total mass loading on the electrode. The electrode was immersed in the electrolyte and activity was measured by linear sweep voltammetry over the potential range of 1.2 to 1.7 V vs. a reversible hydrogen electrode (RHE).

[0090] b) Electrochemical activity Comparison of the inventive sample (BRZ4-AR) with the non-inventive comparative example (H2-PEM-192-1) (see Figure 6) demonstrates the significantly higher activity achieved by the inventive example. Experiments were performed in 0.5 M H2SO4 electrolyte at room temperature under an argon atmosphere. The catalyst was dispersed at 1 wt% in 10:1 H2O / IPA, sonicated to obtain an ink, which was then drop-cast onto a gold electrode. All catalysts were deposited as thin films to achieve the same total mass loading on the electrode. The electrode was immersed in the electrolyte and activity was measured by linear sweep voltammetry over a potential range of 1.2 to 1.7 V vs. a reversible hydrogen electrode (RHE).

[0091] The catalyst of the present invention is stable and active in the acidic oxygen evolution reaction. [Brief explanation of the drawings]

[0092] [Figure 1] TEM image and elemental mapping of a sample of the present invention. [Figure 2] TEM image and elemental mapping of a comparative sample. [Figure 3] 1 is a diffraction pattern of a sample of the present invention. [Figure 4] Diffraction patterns of comparison samples. [Figure 5] a) Stability during electrochemical cycling of the samples of the present invention and b) RuO2. [Figure 6] Electrochemical activity of the samples of the present invention versus the comparative samples.

[0093] References - M. Carmo et al., “A comprehensive review on PEM water electrolysis”, International Journal of Hydrogen Energy, Vol. 38, 2013, pp. 4901-4934 - H.Dau et al.,”The Mechanism of Water Oxidation:From Electrolysis via Homogeneous to Biological Catalysis”,ChemCatChem,2010,2,pp.724-761 - EP 2 608 297 A1 - Reier et al.,”Electrocatalytic Oxygen Evolution Reaction in Acidic Environments-Reaction Mechanisms and Catalysts”Adv.Energy Mater.2017,7,1601275EP 3 581 682 A1 - R.D.Shannon et al.,Inorg.Chem.,21,3372(1982) - WO 2018 / 110423 A1 - Yim et al.,International Journal of Hydrogen Energy 30(2005)1345 - Kamitaka et al.Catalysts 2018,8,258 - Cherevko et al.,”Oxygen and hydrogen evolution reactions on Ru,RuO2,Ir,and IrO2thin film electrodes in acidic and alkaline electrolytes:A comparative study on activity and stability”,Catalysis Today 262(2016)170-180 - Yi et al.,”Effect of Pt introduced on Ru-based electrocatalyst for oxygen evolution activity and stability”,Electrochemistry Communications 104(2019)106469) - A.S.Arico et al.,”Electrochemical analysis of high temperature methanol electro-oxidation at Pt-decorated Ru catalysts”,Journal of Electroanalytical Chemistry 576(2005),pages 161 to 169 - Qing Yao et al.,”A trace of Pt can significantly boost RuO2for acidic water splitting”,Chinese Journal of Catalysis 43(2022),pages 1493 to 501

Claims

1. Ruthenium oxide, RuO ２ and RuO ２ and particles containing a lattice structure, wherein the RuO ２ The particles have at least one transition metal (M) oxide deposited on the particle surface, where M=Pt, Rh, Pd, Ag and / or Au, and the transition metal (M) oxide comprises less than 1 wt. % of RuO, calculated as element M, relative to the total mass of the catalyst composition. ２ The catalyst composition is present in a phase.

2. 2. The catalytic composition according to claim 1, wherein the proportion of the transition metal (M) oxide in the lattice structure is less than 0.5% by weight, relative to the total mass of the catalytic composition.

3. The transition metal (M) oxide is present in an amount of less than 0.5 wt. % of RuO, calculated as element M, relative to the total mass of the catalyst composition. ２ 3. The catalyst composition of claim 1, wherein the catalyst composition is present in a phase.

4. 4. The catalytic composition according to claim 1, comprising less than 2% by weight of elemental transition metal (M) oxides relative to the total mass of the catalyst.

5. 5. The catalytic composition according to claim 1, wherein the average layer thickness of the transition metal (M) oxide coating is in the range of 1 nm to 5 nm.

6. The RuO ２ 6. Catalytic composition according to at least one of claims 1 to 5, wherein the crystallite size of the phase ranges from 2 nm to 60 nm as measured by XRD.

7. The RuO ２ 7. Catalytic composition according to claim 1, wherein the particle size of the phases is on average between 5 and 150 nm, characterized by TEM measurements.

8. 8. The catalytic composition according to claim 1, comprising, relative to the total mass of the catalyst, 1 to 20% by weight of transition metal (M) oxide, 55 to 75% by weight of ruthenium, and the remaining amount of oxygen up to 100% by weight.

9. 9. Catalytic composition according to at least one of claims 1 to 8, wherein the transition metal (M) oxide is platinum, rhodium and / or palladium, preferably the transition metal (M) oxide is platinum.

10. Ruthenium oxide, RuO ２ and RuO ２ and particles containing a lattice structure, wherein the RuO ２ the particles have a transition metal (M) oxide deposited on the particle surface, where M=Pt, Rh, Pd, Ag and / or Au; The transition metal (M) oxide is present in an amount of less than 1 wt. % of RuO, calculated as element M, relative to the total mass of the catalyst composition. ２ present in the phase Catalyst composition, wherein the catalyst composition comprises less than 1 wt. % of the elemental transition metal (M), based on the total mass of the catalyst.

11. A process for obtaining a catalytic composition, said composition comprising ruthenium oxide, RuO ２ and RuO ２ and particles containing a lattice structure, ２ the particles have a transition metal (M) oxide deposited on the particle surface, where M=Pt, Rh, Pd, Ag and / or Au; The transition metal (M) oxide is present in an amount of less than 1 wt. % of RuO, calculated as element M, relative to the total mass of the catalyst composition. ２ present in the phase The process comprises: (a) mixing a predetermined amount of Pt oxide and Ru precursor; (b) subjecting the raw material mixture to a solid-state reaction; (c) removing by-products from the resulting reaction mixture.

12. 12. A catalyst composition obtainable or obtained by the process of claim 11.

13. 13. The catalyst composition of claim 12, comprising less than 1 wt. % of said elemental transition metal (M) relative to the total mass of said catalyst.

14. An electrochemical device comprising the catalyst composition of any one of claims 1 to 9, or comprising the catalyst composition of claim 10, 12 or 13.

15. Use of a catalyst composition according to any one of claims 1 to 9 or according to claims 10, 12 or 13 as a catalyst for the oxygen evolution reaction.

Images