Material suitable for electrocatalytic oxygen evolution reaction

Abstract

The disclosure regards a material for electrocatalytic oxygen evolution reaction (OER) comprising co-doped strontium titanite, wherein the co-dopants comprise at least a first transition metal (M1) and a second transition metal (M2) with the general composition Sr(Ti1-y-zM1yM2z)O3-δ, wherein the atomic fraction of titanium (1-y-z) is > 0.35.5

Description

[0001] Material suitable for electrocatalytic oxygen evolution reaction

[0002] Technical field

[0003] The present disclosure relates to a material suitable for electrocatalytic oxygen evolution reaction (OER), particularly suitable for OER in an electrolysis cell, such as an alkaline water electrolysis cell (AEL or AEMEL) or a water and / or steam electrolysis cell (SEL or LT-SEL). The disclosure further relates to an electrolysis cell comprising an electrocatalytic material, a method of synthesizing an electrocatalytic material, and a method of electrocatalysis.

[0004] Background

[0005] Technologies for producing alternatives to fossil fuels are receiving increasing focus in view of the green transition. Power-to-X is in this context considered a key technology, where surplus renewable energy, e.g. surplus wind or solar power, is converted by electrolysis into carbon-neutral synthetic fuels, such as hydrogen. Hydrogen produced by electrolysis using renewable electricity is accordingly also referred to as green hydrogen.

[0006] Green hydrogen may be produced by splitting water and / or steam into hydrogen (H2) and oxygen (O2) using electricity. This can be obtained with different electrolysis processes and electrolysis cells, such as alkaline water electrolysis (AEL or AEMEL) cells, water and / or steam electrolysis (SEL or LT-SEL) cells, and proton exchange membrane water electrolysis (PEM) cells.

[0007] The efficiency of an electrolysis process may be improved by the electrode materials for respectively the electrocatalytic hydrogen evolution reaction (HER) and the electrocatalytic oxygen evolution reaction (OER). For example, materials and compositions with higher electrocatalytic activity, e.g. accelerated reaction kinetics and / or selectivity for the electrolysis reactions, will result in a more efficient electrolysis. The efficiency of the process may further be improved by electrode materials with higher stability, i.e. materials less prone to degradation during the reaction conditions, such that a high electrocatalytic activity may be maintained during operation.

[0008] The electrolysis efficiency is particularly limited by the oxygen evolution reaction (OER). Thus, electrode materials and compositions with improved electrocatalytic activity and / or selectivity for OER, and improved stability under relevant OER operation conditions are of high relevance.

[0009] Summary

[0010] The present disclosure provides a material suitable as an electrocatalytic material particularly for oxygen evolution reaction (OER) having improved stability, and improved, controllable activity, particularly under high current densities and highly caustic and oxidizing conditions, such as the operating conditions of an alkaline water electrolysis (AEL or AEMEL) cell or a water and / or steam electrolysis cell (SEL or LT- SEL) under alkaline conditions. Accordingly, the material may provide improved efficiency of the electrolysis process.

[0011] The advantageous properties are obtained by a material comprising co-doped strontium titanite, where the two different co-dopants comprise at least a first transition metal (M1) and a second transition metal (M2), and where the atomic fraction, corresponding to the atomic percent, of titanium (Ti) is above 0.35 or 35 at% of the B- site cations.

[0012] A first aspect of the disclosure relates to a material suitable for electrocatalytic oxygen evolution reaction (OER) comprising co-doped strontium titanite, wherein the codopants comprise at least a first transition metal (M1) and a second transition metal (M2) with the general composition Sr(Tii-y-zM1yM2z)O3-5, wherein the atomic fraction of titanium (1-y-z) is > 0.35.

[0013] It is found a material where the two different co-dopants comprise iron (Fe) and nickel (Ni), is specifically suitable as an electrode material for an electrolysis cell, due to a surprisingly improved stability under the relevant operational conditions.

[0014] It is further found that the co-doped strontium titanite, where the atomic fraction or atomic percent of iron (Fe) is below the atomic percent of titanium (Ti), is particularly stable. The doping further facilitates an improved and controllable catalytic activity and a surprisingly better performance at higher current densities.

[0015] A second aspect of the disclosure relates to a material suitable for electrocatalytic oxygen evolution reaction (OER), comprising co-doped strontium titanite, wherein the co-dopants comprise iron (Fe) and nickel (Ni) with the general composition Sr(Tii.y.zFeyNiz)O3-5 (STFN), wherein the atomic fraction of Ti is above the atomic fraction of Fe, such that (1-y-z) > y.

[0016] A third aspect of the disclosure relates to an electrolysis cell, comprising a material suitable for electrocatalytic oxygen evolution reaction (OER), comprising the material according to the first and / or second aspect.

[0017] A fourth aspect of the disclosure relates to a method of synthesizing an electrocatalytic material, comprising the steps of: providing precursors for co-doped strontium titanite, wherein the co-dopants comprise iron (Fe) and nickel (Ni), solid state reacting the precursors into co-doped strontium titanite with the general composition Sr(Ti,Fe,Ni)C>3 (STFN), optionally subjecting the co-doped strontium titanite to a reducing atmosphere at a predefined temperature, whereby FeNi particles are exsolved to a surface or the surfaces of the material.

[0018] In a preferred embodiment, the method of the third aspect is configured to synthesize the material according to the first and / or second aspect. In a further preferred embodiment, the material of the first and / or second aspect is obtained by the method according to the fourth aspect.

[0019] A fifth aspect of the disclosure relates to a method of electrocatalysis, comprising the steps of: providing a material suitable for electrocatalytic oxygen evolution reaction (OER), comprising co-doped strontium titanite, wherein the co-dopants comprise at least a first transition metal (M1) and a second transition metal (M2) with the general composition Sr(Tii-y.zM1yM2z)O3-5, wherein the atomic fraction of titanium (1-y-z) is > 0.35, subjecting the material to electrolysis, where the material is configured for OER.

[0020] In a preferred embodiment of the fifth aspect facilitating surprising high stability, the electrolysis is carried out at temperatures configured for a selected electrolysis cell, such as between 500-1000°C or 800-900°C (for SOEC and PCCEC version of SEL), between 10-500°C (for water and / or steam SEL and for supercritical water), or below 100°C, such as between10-100°C, for AEL. Preferably, the method is carried out at temperatures between 25-900°C or 30-800°C, more preferably between 35-750°C, 40- 600°C or 45-500°C, and most preferably below 150°C or below 100°C, such as at 70, 85, 100, or 120°C.

[0021] In a preferred embodiment, the method of the fifth aspect is configured to be carried out in the electrolysis cell of the third aspect, and / or configured for the material provided according to the first and / or second aspect, such as an electrolysis cell, comprising the material according to the first and / or second aspect.

[0022] In a preferred embodiment of the aspects, the material is configured as an electrocatalytic material.

[0023] Description of Drawings

[0024] The invention will in the following be described in greater detail with reference to the accompanying drawings.

[0025] Figure 1 shows different types of water / steam electrolysis cells respectively (A) alkaline water electrolysis cell, (B) water and / or steam electrolysis cell, (C) proton exchange membrane water electrolysis cell. shows an embodiment of an alkaline water electrolysis cell and the HER electrode and OER electrode.

[0026] Figure 3 shows results from Example 1 where (A) shows XRD of different STFN compositions, (B) shows EDX for a bulk composition, and (C) shows XPS for a surface composition.

[0027] Figure 4 shows results from Example 1 with micrographs of the exsolved FeNi particles, where (A-B) shows a FeNi particle before exposure to air and that the exsolved particle comprise a uniform mixture of Fe and Ni atoms as shown in (B), (C-

[0028] D) shows the particle after exposure to air at room temperature and exsolution at 600 °C, and that the exsolved particle comprise a uniform mixture of Ni, Fe, O atoms as shown in (D), and (E) shows a core shell particle after exposure to air at room temperature and exsolution at 800 °C.

[0029] Figure 5 shows XRD results from Example 1 where different STFN compositions have been subjected to accelerated stress test under alkaline conditions. Figure 6 shows an embodiment of the electrochemical test procedure, as described in Example 2.

[0030] Figure 7 shows results from Example 2, where the performance of STFN with a higher and lower Fe contents are compared by CPs at benchmark current density of 10 mA / cm2.

[0031] Figure 8 shows results from Example 2, where the performance of STFN with a higher and lower Fe contents are compared by LSVs.

[0032] Figure 9 shows results from Example 2, where the performance of STFN with lower Fe content is compared with alternative materials than titanites at benchmark current density of 10 mA / cm2.

[0033] Figure 10 shows results from Example 2 of a long-term test where pristine STFN is operated at a fixed current density and 100°C.

[0034] Figure 11 shows results from Example 2, where (A) shows the test station, and (B) a cross sectional view of a new holder that was employed to enable testing of pellets, showing the placement of the used gasket. The holder was used in all tests for pellets. Figure 12 shows results from Example 2 of a long-term test where pristine STFN is operated at a fixed current density and 150°C.

[0035] Figure 13 shows results from Example 2, showing LSVs curves measured with RDE for the STFN (SrogsTioyFeo^sNioosOp-sj) as pristine or exsolved, and a corresponding STF (SrTio.8Feo.2C>3-d) without co-dopant.

[0036] Figure 14 shows results from Example 2, which shows XRD before and after stability testing the pristine STFN compositions with a higher and lower Fe contents.

[0037] Detailed description

[0038] The invention is described below with the help of the accompanying figures. It would be appreciated by the people skilled in the art that the same feature or component of the device are referred with the same reference numeral in different figures. A list of the reference numbers can be found at the end of the detailed description section.

[0039] Electrolysis cell

[0040] Different electrolysis processes may be carried out in different types of electrolysis cells. An electrolysis cell is generally an electrochemical device, where electrochemical reactions occur at the two electrodes (anode and cathode) of the cell, where the electrodes are separated by a membrane, diaphragm, or electrolyte. Generally, a reduction reaction in the form of hydrogen evolution reaction (HER) occurs at the cathode, and an oxidation reaction in the form of oxygen evolution reaction (OER) occurs at the anode.

[0041] The specific electrochemical reactions that occur at the electrodes are further determined by the specific materials of the electrodes, the material of the electrolyte, and the reaction reactants provided to the cell.

[0042] Table 1 shows an overview of the different types of water / steam electrolysis cells, and Figure 1 shows schematics of the three types of cells (AEL, SEL, PEM) and the associated flow of reaction reactants and products. Alkaline water electrolysis (AEL) is also referred to as AEC or AWE. High temperature steam electrolysis (SEL) is also referred to as SOEC or HT-SEL. Proton exchange membrane water electrolysis (PEM) is also referred to as PEM EC or PEM WE. Cells based on proton conducting ceramic membranes (PCCEL) may be considered similar to PEM in ionic conduction, but may be operated at higher temperatures e.g. 300-800°C and with steam as reactant, and may thus also be considered similar to SEL. In addition to the three types of cells in Figure 1, Table 1 also includes anion exchange membrane electrolysis (AEM or AEMEL) which may be considered similar to AEL, and low temperature steam electrolysis (LT-SEL).

[0043] Tabel 1. The different types of water / steam electrolysis cells. It follows that the electrode reactions and the ionic charge carrier through the separating membrane or electrolyte is different for the different types of cells, and that consequently the environment and electrode operation conditions are significantly different. Accordingly, the skilled person within the field knows that different electrode materials are needed for the different applications, since an electrode material working well in one environment such as SEL, may not be working well in AEL. The differences between the electrolysis cells are further described as below.

[0044] For example, SEL or HT-SEL is based on a reaction splitting water into oxygen ions (O2-) and a membrane capable of conducting the oxygen ions. Consequently, the SEL membrane material is a solid that needs to be operated at elevated temperatures, such as above 500°C, to facilitate sufficient oxygen ion conductivity of the solid material. A further consequence is that the electrode reactions occur at a solid-gas interface. The hydrogen evolution reaction (HER) at the cathode is illustrated by equation (1), and the oxygen evolution reaction (OER) at the anode is illustrated by equation (2).

[0045] (Eq. 1) Cathode:

[0046] (Eq. 2) Anode:

[0047] In contrast, AEL, AEMEL and LT-SEL is based on a reaction splitting water into hydroxide (OH-) and an aqueous alkaline solution as electrolyte. The AEL implies operation under highly alkaline conditions and lower temperatures, such as below 90 or below 110°C, and that the electrode reactions occur at a solid-liquid interface for the AEL. The AEMEL may be operated using less strong alkaline solutions, e.g. diluted KOH or water, and the electrode reactions occur at solid-polymer-gas interface for AEMEL, and at solid-liquid-gas interface for LT-SEL. The hydrogen evolution reaction (HER) at the cathode is illustrated by equation (3), and the oxygen evolution reaction (OER) at the anode is illustrated by equation (4).

[0048] (Eq. 3) Cathode:

[0049] (Eq. 4) Anode:

[0050] Figure 2 shows a schematic close-up of an embodiment of an alkaline water electrolysis cell 1. The anode 1.1 or the HER electrode is seen to the left, and the cathode 1.2 or OER electrode is seen to the right, and the two electrodes are separated by the hydroxide conducting electrolyte 1.3. Advantageously, the electrode has a microstructure formed by multiple pristine or first particles 2, optionally where the first particle is an agglomerate of primary particles as indicated by the dots in Figure 2. Thus, the first particle has an apparent diameter, as indicated by arrow in Figure 2, and with interparticle porosity 3 with an apparent pore diameter, also indicated by arrow in Figure 2. The porous electrode structure may be saturated with the aqueous electrolyte to extend the electrode reaction sites, and the electrolyte present in the porosity of the cathode is referred to as catholyte, and the electrolyte present in the porosity of the anode is referred to as anolyte.

[0051] It follows that an electrolysis cell may be configured for different electrolysis processes depending on the selected material of the cell components, e.g. the electrolyte, and the operational conditions, e.g. operational temperature and reactants that are either water or steam.

[0052] In an embodiment of the disclosure, the electrolysis cell is configured as an alkaline water electrolysis (AEL or AEMEL) cell. In an alternative embodiment, the cell is configured as a water and / or steam electrolysis (SEL or LT-SEL) cell.

[0053] An electrolysis cell comprises a positive and a negative electrode or terminal. When the terminals are connected to an external circuit, the cell may be used to either store electrical energy from the external circuit (i.e. the cell is charging), or the cell may supply power to the external circuit (i.e. the cell is discharging or loading).

[0054] During electrolysis, also referred to as charging mode, the supplied electrical energy is converted and stored as electrochemical products, e.g. hydrogen, by electrochemically reacting electrochemical reactants within the cell. During discharging, also referred to as battery mode, the electrochemical reactions are reversed, and the hydrogen may be a reactant and current is released.

[0055] It follows that the electrochemical roles of the electrodes swap between charging and discharging mode. Accordingly, the positive electrode is cathode in discharging mode and becomes anode in charging mode, and the negative electrode is anode in discharging mode and becomes cathode in charging mode. Thus, an electrolysis cell may implicitly be suitable for being operated in both charging and discharging modes, and the operational mode only depends on the direction of the current to the battery, i.e. the current being either supplied to the battery (charging), or provided by the battery (discharging). An electrolysis cell may accordingly be referred to as a reversible cell.

[0056] An electrolyser or a battery may comprise one electrochemical cell or a multiple of electrically connected cells, also known as a stack or a stack of electrochemical cells. The cells may be electrically connected by interconnects, such that e.g. each cell is sandwiched between two interconnects. The cells, interconnects, and stacks may have any form. For example, the cells may have a planar form, thus consisting of planar layers of electrodes, electrolyte, and optionally interconnects. Alternatively, the cells may have a tubular form, consisting of concentric tubes of electrodes, electrolyte, and optionally interconnects.

[0057] Electrocatalytic material

[0058] To improve the efficiency of the electrolysis process, the electrodes advantageously comprise an electrocatalytic material. By the term “electrocatalytic material” is meant a material that may catalyse the electrochemical reactions, i.e. increase the rate of the chemical reaction. Advantageously, the electrochemical material may further increase the selectivity of a chemical reaction, e.g. for system where multiple reaction products are possible, the electrocatalyst may favour a specific product, e.g. hydrogen, such that the majority of the electricity is utilised for hydrogen production.

[0059] Perovskites are a group of materials that may catalyse the OER for an electrolysis cell. Perovskites have the general chemical formulas: A2+B4+(X2')3, A3+B3+(X2')3, or A1+B5+(X2-)3, where A, B, and X denotes different elements with the indicated valencies. X is typically oxygen, and the formula is then ABO3.

[0060] An example of a perovskite is strontium titanate SrTiCh. The properties of a perovskite may be significantly altered or modified by dopants or doping elements. For example, doping strontium titanate with niobium may change the material from being an insulator to being electrically conductive. The doping involves replacing a part of the titanium atoms (Ti4+) at the B-sites in the perovskite lattice with niobium (Nb5+), such that the general chemical formula becomes: Sr(Ti,Nb)O3-s. Due to the different valency of the dopant, the charge of the perovskite lattice is balanced by a stochiometric deficiency in oxygen indicated by 8, and / or by electronic defects (localized / delocalized electrons or electron holes) and / or the amount of Sr.

[0061] It is found that strontium titanate, where the B-site is doped with more than one element may be particularly advantageous for electrolysis. This co-doping with at least two different elements may involve replacing part of the titanium atoms (Ti4+) at the B- sites in the perovskite lattice with a first transition metal (M1) and a second transition metal (M2) with the general composition Sr(Tii-y-zM1yM2z)O3-5. It is further found that the co-doped strontium titanite with a high fraction of titanium, specifically with an atomic fraction above 0.35, may be particularly stable and / or high performing at e.g. higher current densities. Advantageously, the transition metals are selected from period 4 of the periodic table and / or from groups 5 and 6, and preferably selected from group 4 transition metals of: V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

[0062] In an embodiment of the disclosure, the electrolysis cell comprises an electrocatalytic material suitable for electrocatalytic OER.

[0063] In an embodiment of the disclosure, the material suitable for electrocatalytic oxygen evolution reaction (OER), comprises co-doped strontium titanite, wherein the codopants comprise at least a first transition metal (M1) and a second transition metal (M2) with the general composition Sr(Tii-y-zM1yM2z)O3-5, wherein the atomic fraction of titanium (1-y-z) is > 0.35. In a further embodiment, M1 and M2 are selected from the group of: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ta, and / or W, more preferably from: V, Cr, Mn, Fe, Co, Ni, Cu, and / or Zn, and most preferably are selected from: Fe and Ni, optionally wherein M1 is Fe and M2 is Ni.

[0064] It follows that in addition to having advantageous electrocatalytic properties, particularly for OER, the material may provide similar advantageous electrocatalytic properties at high oxygen partial pressures and / or positive potential for other applications, e.g. oxygenation and / or deoxygenation reactions, preferably in an alkaline environment. Further, the material may in addition advantageously be used as a conductive coating, specifically under alkaline conditions.

[0065] STFN composition In a preferred embodiment, the co-dopants comprise iron (Fe) and nickel (Ni) with the general composition Sr(Ti,Fe,Ni)C>3, which is abbreviated STFN.

[0066] The STFN composition may be varied by substituting variable amounts of iron or nickel atoms into the B-sites of the perovskite lattice. Thus, the composition may be described by the atomic fraction or percent of Ti atoms, Fe atoms, and Ni atoms present in the lattice relative to the amount of B-sites available, such as in the lattice of a unit cell with a single B-site. The atomic percent of Fe may be indicated by y, and the atomic percent of Ni by z, and consequently the atomic percent of Ti is 1-y-z, such that the general chemical formula becomes: Srx(Tii-y-zFeyNiz)O3-s. It is seen that the charge of the perovskite lattice is balanced by a stochiometric deficiency in oxygen indicated by 8, by a change in Ti valency and / or concentration of extended electronic defects (delocalized electrons and electron holes), and a stoichiometric deficiency in strontium indicated by x.

[0067] It is found that the co-doped STFN with specific amounts and / or ratios of Ti and / or Fe, and optionally Ni, may be surprisingly efficient and stable for the OER, when carried out in an electrolysis cell in charging mode under the highly oxidizing conditions due to the OER producing oxygen, and the highly alkaline conditions due to aqueous alkaline solution as anolyte. For example, STFN compositions with a surprisingly high stability under alkaline electrolysis conditions were seen to include a higher atomic percent of Ti compared to Fe, such as below 0.50 atomic percent of Fe, in combination with above 0 atomic percent of Ni. More specifically, the material may advantageously comprise below 0.30 atom percent of Fe, such as 0.25, and 0.05 atomic percent of Ni. For example, the material may comprise or consist of Sro.gsTio.yFeo^sNio.osO^-s).

[0068] In an embodiment of the disclosure, the co-dopants comprise iron (Fe) and nickel (Ni) with the general composition Sr(Tii-y-zFeyNiz)O3-5 (STFN), wherein the atomic fraction of Ti is above the atomic fraction of Fe, such that (1-y-z) > y. In a further embodiment, 0.05 < y < 0.50, and / or wherein 0 < z < 0.10. In a further embodiment, the atomic fraction of iron (y) is between 0.01 - 0.70, more preferably between 0.10 - 0.40, and most preferably between 0.20 - 0.30, such as 0.25. In a further embodiment, the atomic percent of nickel (z) is between 0.01 - 0.10, more preferably between 0.02 - 0.08, and most preferably between 0.03 - 0.0.7, such as 0.04, 0.05, or 0.06. In a further embodiment, the material comprises or consists of Sro.gsTio.yFeo^sNio.osO^-s). Example 1 describes embodiments of the electrocatalytic material, where the stability of the material under alkaline electrolysis conditions is seen to increase, when the Fe content is decreased and below 0.50 atomic percent. Further, Example 2 describes that the material may have improved electrocatalytic activity for OER, specifically at higher current densities.

[0069] STFN microstructure

[0070] The STFN material advantageously has a microstructure comprising a packing of multiple first particles 2 having the STFN composition and with interparticle pores 3, as shown in Figure 2. Optionally, the first particle is an agglomerate particle formed by multiple primary particles.

[0071] Particles and pores of a structure are generally not spherically shaped, but will have an irregular shape, and may form an irregular, interconnected network with neighbouring particles and pores. Thus, the size cannot be unambiguously defined by a diameter or radius. Further, the particle sizes and pore sizes of a structure are generally non- uniform and will form a distribution.

[0072] When applying the common techniques as known to the skilled person for evaluating particle sizes, the size is often quantified in terms of a representative particle diameter, such as the average particle diameter. For example, the size of non-spherical particle may be quantified as the diameter of an equivalent sphere or cylinder, such as the sphere / cylinder having the same volume or surface area as the non-spherical particle. Alternatively, the particle size may be measured indirectly as the absolute surface area (in m2) or the specific surface area (in m2 / g material). Despite this is not a proper quantification from a geometrical point of view, it is applied to provide a quantitative description of the characteristic size.

[0073] The term “particle size distribution” refers to the range of sizes that particles in a material or structure have. Particle size distribution is typically expressed in terms of the range of particle diameters present within the material. It can be described using various metrics, such as the mean particle size, median particle size, and the distribution's width. A narrow particle size distribution indicates that the majority of particles are close in size, while a broader distribution indicates a wider range of particle sizes.

[0074] Particle size and particle size distribution can be determined in multiple ways as it will be known to someone of skill in the art. For example: laser diffraction, sieve analysis, electron microscopy in combination with imaging techniques. For example, the particle sizes may be evaluated by TEM microscopy as described in Example 1.

[0075] Similarly, when applying the common techniques as known to the skilled person for evaluating pore sizes, the pore size is often quantified in terms of a representative pore diameter or pore cylinder diameter, such as the average pore / cylinder diameter. For example, the size of non-spherical pore may be quantified as the diameter of an equivalent sphere or cylinder, such as the sphere / cylinder having the same volume or surface area as the non-spherical pore. Alternatively, the pore size may be measured indirectly by the gas pressure required to displace a liquid within a pore, as measured by capillary flow porosimetry and Young-Laplace formula. Despite this is not a proper quantification from a geometrical point of view, it is applied to provide a quantitative description of the characteristic sizes.

[0076] The term “pore size distribution” refers to the range of sizes that pores or openings within a material have. The pore size distribution is typically expressed in terms of the range of pore diameters present within the material. It can be described using various metrics, such as the mean pore size, median pore size, and the distribution's width. A narrow pore size distribution indicates that the majority of pores are close in size, while a broader distribution indicates a wider range of pore sizes. A unimodal pore size distribution indicates a material having one peak in the distribution, whereas a multimodal distribution has two or more peaks, e.g. a bimodal pore size distribution has two peaks, and a trimodal pore size distribution has three peaks.

[0077] Pore size and pore size distribution can be determined in multiple ways as it will be known to someone of skill in the art. For example by: capillary flow porometry, liquid intrusion porosimetry, gas adsorption, such as BET among others.

[0078] It is found that STFN may provide sufficiently high and stable electrocatalytic activity for an electrolysis cell, even when operated under harsh alkaline conditions, such as AEL. Further, the co-doped STFN material may provide improved and controllable catalytic activity due to exsolved particles, as described in Example 1. The co-doped STFN material facilitates that particles may be exsolved when the co-doped material is exposed to a reducing atmosphere at a predefined temperature. The exsolved particles form second particles 4 on the surface of the pristine or first particles 2, as illustrated in Figure 4. It is further seen that STFN with sufficiently high and stable electrocatalytic activity may be obtained based on pristine or first particles (i.e. particles before exsolution). It is further seen that STFN with sufficiently high and stable electrocatalytic activity may be obtained based on pristine or first particles (i.e. particles before exsolution) with an average particle diameter of between 0.1-8 pm, as measured by SEM and / or image analysis, as further described in Example 1.

[0079] In an embodiment of the disclosure, the material comprises multiple pristine or first particles, optionally wherein the pristine or first particles have an average particle diameter of between 0.1-8 pm, more preferably between 0.25-6 pm, and most preferably between 0.5-5 pm, such as 1, 2, or 3 pm. In a further embodiment, the material comprises multiple second particles obtained by exsolution from the pristine or first particles.

[0080] The composition and microstructure of the second particles are seen to depend on the exsolution conditions. For example, when the particles are exsolved at higher temperatures, such as 800°C, a higher ratio of Fe / Ni may be obtained, and the particles may obtain a non-uniform core shell structure, as described further in Example 1.

[0081] In an embodiment of the disclosure, the second particles comprise FeNi. In a further embodiment, the second particles comprise between 5-70 at.% Fe, more preferably between 10-60 at.% Fe, and most preferably between 15-50 at.% Fe, such as 27, 29, 31, or 33 at.% Fe. In a further embodiment, the second particles comprise a uniform structure, and / or a core shell structure, and preferably has a uniform structure.

[0082] Advantageously, the particles are exsolved at lower temperatures, such as 600°C, where a higher Ni content, corresponding to a lower Fe / Ni ratio, and a uniform structure may be obtained, as further described in Example 1. In an embodiment of the disclosure, the exsolved or second particles comprise between 30-95 at.% Ni, more preferably between 40-90 at.% Ni, and most preferably between 50-85 at.% Ni, such as 60, 65, 69, 73, 77, 80 or 83 at.% Ni.

[0083] Upon exposure to exsolution conditions for a duration of time, the exsolved particles may grow over time. Following the exsolution, the exsolved particles may be oxidized upon exposure to air. The resulting oxidized exsolved particles may have an average particle diameter of the exsolved second particles of between 3-15 nm, as described in Example 1 (Table 3). For example, the average particle diameter may be between 6-8 nm for exsolution at 600°C, and between 8-15 nm for exsolution at 800°C, During electrolysis, the material and particles may be further oxidized due to the OER and the increasing amount of oxygen present, optionally resulting in further growth of the exsolved particles.

[0084] In an embodiment of the disclosure, the exsolved or second particles in an oxidized state have an average particle diameter of between 3-15 nm, more preferably between 4-13 nm, and most preferably between 6-10 nm, such as 8.1 ± 2.4 nm.

[0085] The STFN material may advantageously be integrated into an electrolysis cell, such as AEL. The stability of the material during the operation conditions may facilitate improved activity and efficiency, particularly at higher current densities, as described in Example 2. In addition, the material may be applied at high oxygen partial pressures and / or positive potential for other applications, e.g. oxygenation and / or deoxygenation reactions, preferably in an alkaline environment, and / or as a conductive coating, preferably under alkaline conditions.

[0086] In an embodiment of the disclosure, the material is configured for oxygen evolution reaction in an electrolysis cell, such as an alkaline water electrolysis cell (AEL or AEMEL), water and / or steam electrolysis (SEL or LT-SEL) cell, optionally in alkaline environment, or configured for oxygenation and / or deoxygenation reactions, preferably in alkaline environment.

[0087] STFN synthesis

[0088] The STFN composition and microstructure will depend on the synthesis route. For cost efficiency, the material may advantageously be synthesized by solid state reacting the corresponding oxide or nitrite precursors. The oxides and / or nitrites are mixed and shaped as a slurry, and subsequently heat treated or sintered to induce the solid state reaction. For example, the mixture may be sintered at 1050°C for 10 h, whereby the desired microstructure of the material may be obtained. Other ways to synthesize STFN is commonly known within the field to include e.g. sol-gel, combustion based methods and similar.

[0089] In an embodiment of the disclosure, the precursors are oxides and / or nitrates, optionally SrCOa, TiO2, Fe2Oa and Ni(NOa)2 - 6H2O. In a further embodiment, the solid state reaction is carried out at a temperature between 800-1200°C, more preferably between 900-1150°C, and most preferably between 1000-1100°C, such as 1050°C. In a further embodiment, the duration of the temperature treatment is between 5-20 h, more preferably between 7-15 h, and most preferably between 9-11 h, such as 10 h.

[0090] The STFN before exsolution may also be referred to as pristine STFN. Depending on the exsolution conditions, the exsolved STFN may comprise second exsolved particles of different composition and microstructure, as described above. For example, the particles may advantageously be exsolved in a reducing atmosphere comprising a low concentration of hydrogen, such as 4 vol% hydrogen, which is non-explosive, and e.g. be carried out at 600°C for 5 hours.

[0091] In an embodiment of the disclosure, the reducing atmosphere comprises hydrogen, preferably hydrogen in lower concentrations, such as 4% H2 196% N2 atmosphere. In a further embodiment, the predefined temperature is between 450-900°C, more preferably between 500-850°C, and most preferably between 550-800°C, such as 600°C. In a further embodiment, the duration of the temperature treatment is up to 40 h, more preferably between 1-30 h, and most preferably between 2-20 h, such as 5, 10, or 15 h.

[0092] Electrolysis operational conditions

[0093] Due to the high stability, the co-doped strontium titanite, such as the STFN material may be integrated into an electrolysis cell, such as AEL, and operated under harsh conditions that may provide higher efficiency due to thermodynamics. For example, the electrolysis cell may be based on a highly caustic electrolyte solution, such as 10 M KOH, and the electrolysis performed at elevated pressure and temperatures. In an embodiment of the disclosure, the electrolysis is carried out with a caustic electrolyte, such as 0.1-15 M KOH, more preferably 1-12 M, such as 10 M KOH. In a further embodiment, the electrolysis is carried out at elevated pressures, such as 10- 100 bar, more preferably 20-80 bar, and most preferably 30-60 bar, such as 40 or 50 bar.

[0094] The co-doped strontium titanite, such as the STFN material with a high atomic fraction of titanium, may show surprisingly high stability under electrolysis conditions, such as alkaline AEL and / or SEL. For example pristine SrogsTio.yFeo^sNio.osO^-s) may be surprisingly stable, as described in Example 1. Furthermore, exsolved Sro.98Tio.7Feo.25Nio.o50(3-5) may be surprisingly stable, particularly for AEL electrolysis carried out at temperatures below 100°C.

[0095] In an embodiment of the disclosure, the electrolysis is carried out at temperatures of between of between 25-900°C or 30-800°C, more preferably between 35-750°C, 40- 600°C or 45-500°C, and most preferably below 150°C or below 100°C, such as at 70, 85, 100, or 120°C.

[0096] Reference numbers

[0097] 1 - Cell

[0098] 1.1 - Anode

[0099] 1.2 - Cathode

[0100] 1.3 - Membrane or electrolyte

[0101] 2 - First particles or agglomerates

[0102] 3 - Porosity

[0103] 4 - Second particles

[0104] Examples

[0105] The invention is further described by the examples provided below.

[0106] STFN compositions (pristine) may be synthesized using conventional solid-state reaction as further described below for the example of Sro.gsTio.yFeo^sNio.osO^-s). Other ways to synthesize STFN is commonly known within the field to include e.g. sol-gel, combustion based methods and similar.

[0107] Sro.98Tio.7Feo.25Nio.o50(3-5) has been synthesized using conventional solid-state reaction. Stoichiometric ratios of SrCCh, TiC>2, Fe2Oa and Ni(NOa)2 • 6H2O were dissolved in ethanol and ball milled for 24 h. Afterwards, the powder (first particles or agglomerates) was dried and sintered at 1050°C for 10 h.

[0108] Thereafter, the material was pressed into pellets with a diameter of 12 mm and a thickness of approximately 2-3 mm. The pellets were sintered at 1300°C for 10 h for densification. Subsequently, the samples were polished to achieve a low surface roughness.

[0109] For the synthesis described above, the pristine or first particles (i.e. the particles before exsolution) may have an average particle diameter between 0.5-5 pm as measured by scanning electron microscopy (SEM). By changing the synthesis method, e.g. by decreasing the sintering temperature or duration, a lower average particle diameter may be obtained.

[0110] Some of the samples were exposed to an exsolution process, where FeNi particles (second particles) are exsolved to the sample surface. The exsolution was performed in a 4% H21 96% N2 atmosphere at different temperatures from 600°C - 800°C for 1 h, 5 h, or 30 h.

[0111] The samples were subsequently exposed to air at room temperature for oxidizing the particles, which also occurs during the OER.

[0112] Results - XRD and EDX

[0113] Samples of different STFN compositions were investigated by X-ray diffraction (XRD) using Panalytical Aeris equipped with a Cu-Ka x-ray source. The examined samples were pristine, i.e. examined before exposure to exsolution. Figure 3A shows the resulting diffractogram for two samples with different A-site deficiencies, respectively Sro.95Tio.3Feo.65Nio.o50(3-5) (upper curve) and Sro.98Tio.7Feo.25Nio.o50(3-5) (lower curve). It was generally seen that a higher A-site deficiency (including a higher Fe content) results in more secondary phases, due to decomposition being thermodynamically more favorable, and making the material more unstable. For example, secondary phases of NiO and Sr2FeO4 are seen for Sro.gsTio.aFeo.esNio.osO^-s). Hence, it was surprisingly seen that the Fe-Ni co-doped strontium titanite, where the atomic percent of iron (Fe) is below the atomic percent of titanium (Ti), is surprisingly stable.

[0114] The bulk composition of a Sro.gsTio.yFeo^sNio.osO^-s) sample was analyzed by energy- dispersive X-ray spectroscopy (EDX) of type Oxford instrument EDX detector in a Zeiss Merlin operated at 5-1 OkV and a probe current of 100pA. Figure 3B shows a table of the elements. A larger error is associated with trace amounts in the range of 1 %, such as Ni, and may account for the seemingly low amount of Ni in the overall perovskite (3% instead of the expected 5% at the B-site of the perovskite).

[0115] The surface composition of a Sro.gsTio.yFeo^sNio.osO^-s) sample was analyzed by X-ray photoelectron spectroscopy (XPS) using a Thermo Scientific Excalab 250Xi XPS instrument with an Al-Kalpha source (1486.6 eV) run at 15 kV and 10 mA. Figure 3C shows a table of the elements, where a slightly lower Fe concentration is seen at the surface and a surface layer of SrO.

[0116] Results - TEM

[0117] The samples were examined by transmission electron microscopy (TEM) of the type Talos F200X. Figure 4 shows micrographs of the exsolved FeNi particles, where (A-B) shows a FeNi particle before exposure to air, and (C-D) shows the particle after exposure to air at room temperature after exsolution at 600-800 °C. It is seen that oxidation makes the particles grow and that the oxidation is homogeneous. The increase in particle diameter was measured by image analysis and summarized in Table 2 below.

[0118] Table 2. Measured particle diameter before and after exposure to air. The average particle diameter after oxidation was seen to depend on the exsolution temperature for the FeNi particles, as summarized in Table 3 below. It was seen that higher exsolution temperatures resulted in larger particles.

[0119] Table 3. Measured average particle diameters (after oxidation) for particles exsolved at different temperatures.

[0120] The composition and microstructure of the particles were also seen to depend on the exsolution temperature, as summarized in Table 4 below. When the particles were exsolved at higher temperatures, a higher ratio of Fe / Ni was observed, and the particles had a core shell structure (shown in Figure 4E) instead of being uniform.

[0121] Table 4. Composition and microstructure (after oxidation) for particles exsolved at different temperatures. For core shell microstructures, the composition marked with refers to the shell composition.

[0122] Results - Stability

[0123] The stability of STFN with varying Ti / Fe ratios was tested in an accelerated stress test under alkaline conditions in 10 M KOH and at 200 °C. The degradation of the samples, and the associated presence of decomposition products, were evaluated by XRD. Diffractograms of the tested samples after exposure to the alkaline conditions are shown in Figure 5. The stability is seen to increase, when the Fe content is decreased. It further appears that sufficient stability may be obtained for an atomic Fe content of 0.25, such as for Sro.98Tio.7Feo.25Nio.o50(3-5). Example 2 - Electrochemical test of STFN

[0124] The electrochemical performance was evaluated using the test setup described by Chatzichristodoulou et al. (High temperature and pressure electrochemical test station, Review of Scientific Instruments 84 (2013)). The test station and a new holder that was employed to enable testing of pellets is shown in Figure 11. The holder shown in Figure 11 B was used in all tests for pellets. The test setup may be configured for AEL operation conditions.

[0125] Dense polished pellets were tested. This was done to ensure that the geometrical surface area matches closely with the electrochemically active surface area (ECSA) and only the intrinsic activities of the samples are compared.

[0126] The measurements were performed in concentrated potassium hydroxide (KOH) with a concentration of 10 M. As the measurements were performed at elevated temperatures and pressures no commercial reference electrode could be used for the test. However, a homemade RHE was used similar to Leuaa et. (Reversible Hydrogen and Pd Hydride Reference Electrodes with Electrochemically Supplied H 2 for High Temperature and Pressure Electrochemistry , J Electrochem Soc 169 (2022) 054534).

[0127] The samples were tested according to the test procedure shown in Figure 6, including measurements before pressurization, during pressurization, and after pressurization. Pressurized tests were performed at elevated pressures of ca. 50 bar and the same pressure was sustained throughout the measurements using a pressure release valve. The same sample was tested at 25°C, 50°C, 75°C, 100°C, 125°C, 150°C and 200°C, i.e. the steps of the pressurized test procedure in Figure 6, was repeated for each temperature.

[0128] As indicated in Figure 6, the measurements included cyclic voltammograms (CVs), linear sweep voltammograms (LSVs), and chronopotentiometry (CP) at a current density of 1-50 mA / cm2. All potentials values are iR-corrected to compensate for the solution resistance, wires and low conductivity of samples, i.e. the electronic transport through the dense polished pellets. The performance was evaluated using linear sweep voltammograms (LSVs) and the overpotential at 10 mA / cm2during a 5 minutes chronopotentiometry averaging over the last 60 s. Results

[0129] The electrochemical performance in terms of the overpotential for different STFN samples are shown in Figures 7-8. Figure 7 compares the performance obtained by CPs for STFN with a higher and lower Fe contents, respectively Sro.gsTio.yFeo^sNio.osO^- 5) (upper and lower curves) and Sro.gsTio.sFeo.esNio.osO^-s) (middle curves). The CPs were carried out at a benchmark current density of 10 mA / cm2. Figure 8 compares the performance as iV-curves obtained by LSV.

[0130] The performance or activity for the STFN with higher and lower Fe contents appear to be comparable for the pristine (i.e. not exsolved) samples, as seen in Figure 7. However, Figure 7 shows that the STFN with the lower Fe content may provide an enhanced catalytic activity upon an exsolution treatment, resulting in the formation of a host-nanoparticle structure, as described in Example 1. Accordingly, a much lower overpotential, e.g. 199 mV at 75°C and 10mA / cm2is seen, corresponding to 85 mV lower than the pristine sample at 75°C.The measured overpotentials are further summarized in Table 5.

[0131] Table 5. Measured overpotentials for pristine and exsolved Sro.gsTio.yFeo^sNio.osO^-s) at different temperatures, and where the exsolution was done at 600 °C.

[0132] Figure 8 further shows that the performance of the lower Fe content sample (curves with steeper slopes) is surprisingly better at higher current densities.

[0133] For further comparison, Figure 9 compares the performance of the STFN with the lower Fe content with alternative materials than titanites, such as perovskite ferrites (LaFeO<3- 5)) and doped ferrites ((La,Sr)FeO<3-5)), doped manganites perovskite ((La,Sr)MnO<3-5)), and Ni / Fe layered double hydroxide (LDH). It is seen that the performance of STFN is generally comparable or better than the alternative materials. The comparison is carried out at a benchmark current density of 10 mA / cm2. The best performance is seen for the lower black curve denoted Ex. 600°C.

[0134] For further comparison, Figure 13 shows LSV curves measured with RDE for the STFN as pristine or exsolved, and a corresponding STF (SrTio.8Feo.2O3-d) without co-dopant. An improved performance of STFN is seen.

[0135] Figures 10 and 12 show long-term tests for approx. 200 hours, where pristine STFN with lower Fe content is operated at a fixed current density of 10 mA / cm2in 40.3 wt% KOH, at 50 bar, and 100°C or 150°C, respectively. The periodic oscillations are due to bubble entrapment and the related lowering of the active surface area (cf. Figure 11). It is seen that (apart from a transient response when transitioning from open circuit conditions to the steady state polarization at 10 mA / cm2) the pristine sample provides excellent stability under relevant electrolyzer conditions.

[0136] Testing indicates that the exsolved STFN with lower Fe content provides excellent stability up to 75°C and under relevant electrolyzer conditions.

[0137] Figure 14 shows XRD before and after accelerated stability testing the pristine STFN compositions with a higher and lower Fe contents, respectively Sro.gsTio.yFeo^sNio.osO^- 5) and Sro.95Tio.3Feo.65Nio.o50(3-5). Improved stability of STFN with lower Fe contents are also seen in this case.

[0138] Conclusions

[0139] STFN with lower Fe content, i.e. with an atomic percent of Fe that is below the atomic percent of Ti, is seen to be surprisingly stable composition, particularly under the harsh conditions relevant for an AEL electrolyzer, such as under alkaline conditions in 10 M KOH and at temperatures up to at least 200 °C (cf. Example 1).

[0140] STFN with lower Fe content is further seen to provide improved electrocatalytic activity for OER. Specifically, this type of STFN facilitates controllable enhancement of the catalytic activity by exsolution treatment, and that the enhancement may be further controlled by the exsolution temperature. This STFN, particularly in pristine form, further provides surprisingly better performance than Fe rich compositions at higher current densities and electrolyzer conditions. Items

[0141] The presently disclosed may be described in further detail with reference to the following items.

[0142] 1 . A material for electrocatalytic oxygen evolution reaction (OER) comprising codoped strontium titanite, wherein the co-dopants comprise at least a first transition metal (M1) and a second transition metal (M2) with the general composition Sr(Tii-y-zM1yM2z)O3-5, wherein the atomic fraction of titanium (1-y-z) is > 0.35.

[0143] 2. The material according to item 1 , wherein M1 and M2 are selected from the group of: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ta, and / or W, more preferably from: V, Cr, Mn, Fe, Co, Ni, Cu, and / or Zn, and most preferably from: Fe and Ni, optionally wherein M1 is Fe and M2 is Ni.

[0144] 3. The material according to item 2 with the general composition Sr(Tii.y. zFeyNiz)O3-5 (STFN), wherein the atomic fraction of Ti is above the atomic fraction of Fe, such that (1-y-z) > y.

[0145] 4. The material according to any one of items 2-3, wherein the atomic fraction of iron (y) is between 0.01 - 0.70, more preferably between 0.10 - 0.40, and most preferably between 0.20 - 0.30, such as 0.25.

[0146] 5. The material according to any one of items 2-4, wherein 0.05 < y < 0.50, and / or wherein 0 < z < 0.10.

[0147] 6. The material according to any one of items 2-5, wherein the atomic percent of nickel (z) is between 0.01 - 0.10, more preferably between 0.02 - 0.08, and most preferably between 0.03 - 0.0.7, such as 0.04, 0.05, or 0.06.

[0148] 7. The material according to any one of the preceding items, comprising or consisting of Sro.98Tio.7Feo.25Nio.o50(3-5).

[0149] 8. The material according to any one of the preceding items configured as an electrocatalytic material. 9. The material according to any one of the preceding items, comprising multiple pristine or first particles, optionally wherein the pristine or first particles have an average particle diameter of between 0.1-8 pm, more preferably between 0.25- 6 pm, and most preferably between 0.5-5 pm, such as 1 , 2, or 3 pm.

[0150] 10. The material according to any one of the preceding items, comprising multiple second particles obtained by exsolution from the pristine or first particles.

[0151] 11. The material according to item 10, wherein the exsolved or second particles comprise FeNi.

[0152] 12. The material according to item 11 , wherein the exsolved or second particles comprise between 5-70 at.% Fe, more preferably between 10-60 at.% Fe, and most preferably between 15-50 at.% Fe, such as 27, 29, 31 , or 33 at.% Fe, and / or wherein the exsolved or second particles comprise between 30-95 at.% Ni, more preferably between 40-90 at.% Ni, and most preferably between 50-85 at.% Ni, such as 60, 65, 69, 73, 77, 80 or 83 at.% Ni.

[0153] 13. The material according to any one of items 10-12, wherein the exsolved or second particles comprise a uniform structure, and / or a core shell structure, and preferably has a uniform structure.

[0154] 14. The material according to any one of items 10-13, wherein the exsolved or second particles in an oxidized state have an average particle diameter of between 3-15 nm, more preferably between 4-13 nm, and most preferably between 6-10 nm, such as 8.1 ± 2.4 nm.

[0155] 15. The material according to any one of the preceding items, configured for oxygen evolution reaction in an electrolysis cell, such as an alkaline water electrolysis cell (AEL or AEMEL), water and / or steam electrolysis (SEL or LT- SEL) cell, optionally in alkaline environment, or configured for oxygenation and / or deoxygenation reactions, preferably in alkaline environment. 16. The material according to any one of the preceding items, obtained by the method according to any one of items 20-27.

[0156] 17. An electrolysis cell, comprising a material for electrocatalytic oxygen evolution reaction (OER), comprising the material according to any one of items 1-16.

[0157] 18. The electrolysis cell according to item 17, configured as an alkaline water electrolysis (AEL or AEMEL) cell.

[0158] 19. The electrolysis cell according to item 17, configured as a water and / or steam electrolysis (SEL or LT-SEL) cell.

[0159] 20. A method of synthesizing an electrocatalytic material, comprising the steps of: providing precursors for co-doped strontium titanite, wherein the co-dopants comprise iron (Fe) and nickel (Ni), solid state reacting the precursors into co-doped strontium titanite with the general composition Sr(Ti,Fe,Ni)C>3 (STFN), optionally subjecting the co-doped strontium titanite to a reducing atmosphere at a predefined temperature, whereby FeNi particles are exsolved to a surface of the material.

[0160] 21. The method according to item 20, wherein the precursors are oxides and / or nitrates, optionally SrCCh, TiC>2, Fe2Oa and Ni(NOa)2 - 6H2O.

[0161] 22. The method according to any one of items 20-21 , wherein the solid state reaction is carried out at a temperature between 800-1200°C, more preferably between 900-1150°C, and most preferably between 1000-1100°C, such as 1050°C.

[0162] 23. The method according to item 22, wherein the duration of the temperature treatment is between 5-20 h, more preferably between 7-15 h, and most preferably between 9-11 h, such as 10 h. 24. The method according to any one of items 20-23, wherein the reducing atmosphere comprises hydrogen, preferably hydrogen in lower concentrations, such as 4% H2196% N2 atmosphere.

[0163] 25. The method according to any one of items 20-24, wherein the predefined temperature is between 450-900°C, more preferably between 500-850°C, and most preferably between 550-800°C, such as 600°C.

[0164] 26. The method according to item 25, wherein the duration of the temperature treatment is up to 40 h, more preferably between 1-30 h, and most preferably between 2-20 h, such as 5, 10, or 15 h.

[0165] 27. The method according to any one of items 20-26, configured to synthesize the material according to any one of claims 1-16.

[0166] 28. A method of electrocatalysis, comprising the steps of: providing a material for electrocatalytic oxygen evolution reaction (OER), comprising co-doped strontium titanite, wherein the co-dopants comprise at least a first transition metal (M1) and a second transition metal (M2) with the general composition Sr(Tii-y-zM1yM2z)O3-5, wherein the atomic fraction of titanium (1-y-z) is > 0.35, subjecting the material to electrolysis, where the material is configured for OER.

[0167] 29. The method according to item 28, wherein the electrolysis is carried out with a caustic electrolyte, such as 0.1-15 M KOH, more preferably 1-12 M, such as 10 M KOH.

[0168] 30. The method according to any one of items 28-29, wherein the electrolysis is carried out at elevated pressures, such as 10-100 bar, more preferably 20-80 bar, and most preferably 30-60 bar, such as 40 or 50 bar.

[0169] 31. The method according to any one of items 28-30, wherein the electrolysis is carried out at temperatures of between 25-900°C or 30-800°C, more preferably between 35-750°C, 40-600°C or 45-500°C, and most preferably below 150°C or below 100°C, such as at 70, 85, 100, or 120°C. The method according to any one of items 28-31 , configured to be carried out in the electrolysis cell of any one of items 17-19, and / or configured for the material according to any one of items 1-16.

Claims

Claims1 . A material for electrocatalytic oxygen evolution reaction (OER) comprising codoped strontium titanite, wherein the co-dopants comprise at least a first transition metal (M1) and a second transition metal (M2) with the general composition Sr(Tii-y-zM1yM2z)O3-5, wherein the atomic fraction of titanium (1-y-z) is > 0.35.

2. The material according to claim 1 , wherein M1 and M2 are selected from the group of: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ta, and / or W, more preferably from: V, Cr, Mn, Fe, Co, Ni, Cu, and / or Zn, and most preferably from: Fe and Ni, optionally wherein M1 is Fe and M2 is Ni.

3. The material according to claim 2 with the general composition Sr(Tii.y. zFeyNiz)O3-5 (STFN), wherein the atomic fraction of Ti is above the atomic fraction of Fe, such that (1-y-z) > y.

4. The material according to any one of claims 2-3, wherein the atomic fraction of iron (y) is between 0.01 - 0.70, more preferably between 0.10 - 0.40, and most preferably between 0.20 - 0.30, such as 0.25.

5. The material according to any one of claims 2-4, wherein 0.05 < y < 0.50, and / or wherein 0 < z < 0.10.

6. The material according to any one of claims 2-5, wherein the atomic percent of nickel (z) is between 0.01 - 0.10, more preferably between 0.02 - 0.08, and most preferably between 0.03 - 0.0.7, such as 0.04, 0.05, or 0.06.

7. The material according to any one of the preceding claims, comprising or consisting of Sro.98Tio.7Feo.25Nio.o50(3-5).

8. The material according to any one of the preceding claims configured as an electrocatalytic material.

9. The material according to any one of the preceding claims, comprising multiple pristine or first particles, optionally wherein the pristine or first particles have anaverage particle diameter of between 0.1-8 pm, more preferably between 0.25-6 pm, and most preferably between 0.5-5 pm, such as 1 , 2, or 3 pm.

10. The material according to any one of the preceding claims, comprising multiple second particles obtained by exsolution from the pristine or first particles.

11. The material according to claim 10, wherein the exsolved or second particles comprise FeNi.

12. The material according to claim 11 , wherein the exsolved or second particles comprise between 5-70 at.% Fe, more preferably between 10-60 at.% Fe, and most preferably between 15-50 at.% Fe, such as 27, 29, 31, or 33 at.% Fe, and / or wherein the exsolved or second particles comprise between 30-95 at.% Ni, more preferably between 40-90 at.% Ni, and most preferably between 50-85 at.% Ni, such as 60, 65, 69, 73, 77, 80 or 83 at.% Ni.

13. The material according to any one of claims 10-12, wherein the exsolved or second particles comprise a uniform structure, and / or a core shell structure, and preferably has a uniform structure.

14. The material according to any one of claims 10-13, wherein the exsolved or second particles in an oxidized state have an average particle diameter of between 3-15 nm, more preferably between 4-13 nm, and most preferably between 6-10 nm, such as 8.1 ± 2.4 nm.

15. The material according to any one of the preceding claims, configured for oxygen evolution reaction in an electrolysis cell, such as an alkaline water electrolysis cell (AEL or AEMEL), water and / or steam electrolysis (SEL or LT- SEL) cell, optionally in alkaline environment, or configured for oxygenation and / or deoxygenation reactions, preferably in alkaline environment.

16. The material according to any one of the preceding claims, obtained by the method according to any one of claims 20-27.

17. An electrolysis cell, comprising a material for electrocatalytic oxygen evolution reaction (OER), comprising the material according to any one of claims 1-16.

18. The electrolysis cell according to claim 17, configured as an alkaline water electrolysis (AEL or AEMEL) cell.

19. The electrolysis cell according to claim 17, configured as a water and / or steam electrolysis (SEL or LT-SEL) cell.

20. A method of synthesizing an electrocatalytic material, comprising the steps of: providing precursors for co-doped strontium titanite, wherein the co-dopants comprise iron (Fe) and nickel (Ni), solid state reacting the precursors into co-doped strontium titanite with the general composition Sr(Ti,Fe,Ni)C>3 (STFN), optionally subjecting the co-doped strontium titanite to a reducing atmosphere at a predefined temperature, whereby FeNi particles are exsolved to a surface of the material.

21. The method according to claim 20, wherein the precursors are oxides and / or nitrates, optionally SrCCh, TiC>2, Fe2Oa and Ni(NOa)2 - 6H2O.

22. The method according to any one of claims 20-21 , wherein the solid state reaction is carried out at a temperature between 800-1200°C, more preferably between 900-1150°C, and most preferably between 1000-1100°C, such as 1050°C.

23. The method according to claim 22, wherein the duration of the temperature treatment is between 5-20 h, more preferably between 7-15 h, and most preferably between 9-11 h, such as 10 h.

24. The method according to any one of claims 20-23, wherein the reducing atmosphere comprises hydrogen, preferably hydrogen in lower concentrations, such as 4% H2 / 96% N2 atmosphere.

25. The method according to any one of claims 20-24, wherein the predefined temperature is between 450-900°C, more preferably between 500-850°C, and most preferably between 550-800°C, such as 600°C.

26. The method according to claim 25, wherein the duration of the temperature treatment is up to 40 h, more preferably between 1-30 h, and most preferably between 2-20 h, such as 5, 10, or 15 h.

27. The method according to any one of claims 20-26, configured to synthesize the material according to any one of claims 1-16.

28. A method of electrocatalysis, comprising the steps of: providing a material for electrocatalytic oxygen evolution reaction (OER), comprising co-doped strontium titanite, wherein the co-dopants comprise at least a first transition metal (M1) and a second transition metal (M2) with the general composition Sr(Tii-y-zM1yM2z)O3-5, wherein the atomic fraction of titanium (1-y-z) is > 0.35, subjecting the material to electrolysis, where the material is configured for OER.

29. The method according to claim 28, wherein the electrolysis is carried out with a caustic electrolyte, such as 0.1-15 M KOH, more preferably 1-12 M, such as 10 M KOH.

30. The method according to any one of claims 28-29, wherein the electrolysis is carried out at elevated pressures, such as 10-100 bar, more preferably 20-80 bar, and most preferably 30-60 bar, such as 40 or 50 bar.

31. The method according to any one of claims 28-30, wherein the electrolysis is carried out at temperatures of between 25-900°C or 30-800°C, more preferably between 35-750°C, 40-600°C or 45-500°C, and most preferably below 150°C or below 100°C, such as at 70, 85, 100, or 120°C.

32. The method according to any one of claims 28-31 , configured to be carried out in the electrolysis cell of any one of claims 17-19.

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