Perovskite-based composite catalyst loaded with cobalt-iron-nickel alloy in situ, preparation of perovskite-based composite catalyst and application of perovskite-based composite catalyst in OER catalysis

Abstract

The invention belongs to the field of OER catalysis, and particularly discloses a preparation method of a perovskite-based composite catalyst for surface in-situ desolvation of cobalt-iron-nickel ternary alloy nanoparticles, a perovskite precursor material with the expression formula of A-site defects being A1-xBO3-delta is obtained, and then the perovskite precursor material is roasted in a hydrogen-containing atmosphere at the temperature of 340-410 DEG C to obtain the perovskite-based composite catalyst for surface in-situ desolvation of cobalt-iron-nickel ternary alloy nanoparticles, in the A1-xBO3-delta, A is alkaline earth or a rare earth metal element, B comprises Co, Fe and Ni, and x is more than or equal to 0.85 and less than 1. The invention also comprises the catalyst prepared by the preparation method and the OER catalytic application of the catalyst. The preparation method provided by the invention can be used for preparing materials with special physicochemical and structure and excellent OER catalytic activity.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic water decomposition, and in particular to the field of water electrolysis OER catalytic materials. Background Art

[0002] The growth of global energy demand is often a manifestation of the booming social economy. Fossil fuels have brought convenience to our lives, but their excessive consumption has caused huge adverse effects on the environment. The rational use and effective conversion of energy have become two important issues in the development of today's energy industry. The exploration of renewable energy has important strategic significance for the sustainable development of today's society. As an ideal, green and efficient renewable energy, hydrogen energy has the characteristics of high calorific value, abundant sources, environmental friendliness and wide application range. It has received more attention in many national and international strategies. Hydrogen is produced by electrolysis of water, and pure oxygen is the only by-product. From the perspective of environmental protection and sustainable development, electrolysis of water is currently the best way to produce hydrogen. The oxygen evolution reaction (OER) at the anode of the electrolytic water involves multiple steps of protons (H + ) transfer process, which has slow kinetics, is the most energy-consuming step in water electrolysis. Therefore, the development of green, cheap, efficient and highly stable oxygen evolution reaction catalysts has become an important topic in the current energy field.

[0003] Perovskite oxides have become a research hotspot in OER catalysts in recent years due to their flexible and stable crystal structure and unique physical and chemical properties. The general structural formula of perovskite oxides is ABO3, where the A position is usually an alkaline earth or rare earth metal element, and the B position is generally a transition metal element with multiple valence states. The metal ions at the A position play a role in stabilizing the crystal structure, while the B position is a transition metal ion with variable valence states, which gives the material special physical and chemical properties. However, the electronic conductivity and intrinsic catalytic activity of perovskite oxides are relatively low, which has become a difficulty in catalyst research.

[0004] At present, one of the important ways to improve the oxygen evolution activity of perovskite catalysts is to combine them with alloy particles with high electrical conductivity for oxygen evolution reaction in water electrolysis. The interaction between the two phases at the contact interface changes the electronic structure of the perovskite oxide. The unique synergistic effect improves the conductivity of the catalyst, making the catalytic activity of the composite material better than that of the single-component counterpart. However, the current methods for preparing composite catalysts of perovskite oxides and active substances are generally traditional vapor deposition methods, ball milling mixing methods, and wet chemical impregnation methods. These methods make it difficult to precisely control the size and density of surface metal nanoparticles, and the interaction between the perovskite matrix and the metal nanoparticles in the prepared catalyst material is weak. In practical applications, metal nanoparticles will inevitably agglomerate at high temperatures, which often shortens the service life of the catalyst.

[0005] In response to the above-mentioned technical deficiencies, the industry has recently proposed a few improved solutions for dissolution preparation. Although these solutions can improve the effect to a certain extent, the existing dissolution methods are still immature and most of them need to be implemented at relatively high temperatures. It is difficult to effectively control the physical and chemical characteristics, dispersion conditions and bonding ability of the alloy particles with the substrate, and it is difficult to effectively exert the advantages of the dissolution method. The OER performance of the prepared materials still needs to be further improved. Summary of the invention

[0006] In view of the problem that the OER activity and stability of existing perovskite-based composite catalyst materials are not ideal, the first purpose of the present invention is to provide a method for preparing a perovskite-based composite catalyst with in-situ precipitation loaded cobalt-iron-nickel ternary alloy nanoparticles (the present invention is also referred to as an in-situ loaded cobalt-iron-nickel alloy perovskite-based composite catalyst or a perovskite-based composite catalyst), aiming to prepare a material with special composition and structural characteristics and excellent OER activity and cycle stability.

[0007] The second purpose of the present invention is to provide a perovskite-based composite catalyst prepared by the preparation method.

[0008] The third purpose of the present invention is to use the perovskite-based composite catalyst as an OER catalyst, as well as a water electrolysis device comprising the perovskite-based composite catalyst and an anode catalyst thereof.

[0009] A method for preparing a perovskite-based composite catalyst with in-situ surface desolvation of cobalt, iron, and nickel ternary alloy nanoparticles, wherein the expression formula for obtaining the A-site defect is A 1-x BO 3-δ The perovskite precursor material is then calcined in a hydrogen atmosphere at a temperature of 340 to 410° C. to obtain;

[0010] The A 1-x BO 3-δ In which, A is an alkaline earth or rare earth metal element, B includes Co, Fe and Ni, 0.85≤x<1, and δ is the number of oxygen lattice defects.

[0011] The present invention innovatively uses the expression of A-site defect as A 1-x BO 3-δ The perovskite is used as a precursor substrate, and the temperature of the subsequent hydrogen-containing calcination is further jointly controlled. In this way, synergy can be achieved. Co-Fe-Ni ternary alloy particles can be unexpectedly in situ desolvated and precipitated at the temperature, and their dispersion uniformity and physical and chemical bonding ability with the substrate can be improved, thereby synergistically improving the OER activity and catalytic stability of the prepared material.

[0012] In the present invention, the joint control of the defective substrate A and the temperature under the hydrogen-containing atmosphere is the key to synergistically inducing the in-situ dissolution and precipitation of the ternary alloy particles, improving their dispersion and in-situ bonding stability, and improving their OER activity and stability.

[0013] In the present invention, the expression formula of the A-site defect is A 1-x BO 3-δ The perovskite can be prepared based on existing means, preferably by a sol-gel method, the steps of which are, for example: mixing stoichiometric amounts of source A, source B and a complexing aid to perform a sol-gel reaction, followed by foaming and aging to obtain a dry gel, and then performing an oxidative calcination treatment to obtain the perovskite precursor material.

[0014] In the present invention, the A source is a water-soluble salt of metal A, such as at least one of nitrate, metal alkoxide, chloride, and acetate of metal A;

[0015] In the present invention, the A metal can be any alkaline earth metal or rare earth metal element, for example, it can be Sr.

[0016] In the present invention, A is a defect, which helps to coordinate with the subsequent calcination temperature in a hydrogen-containing atmosphere. In the present invention, the x is preferably 0.9 to 0.95, and more preferably 0.9 to 0.92.

[0017] The B source is a water-soluble salt of metal B, preferably at least one of nitrate, metal alkoxide, chloride and acetate of metal B;

[0018] Preferably, in the B metal element, the molar ratio of Co, Fe and Ni is x:y:(1-xy), wherein x is 0.45-0.55: y is 0.3-0.4 (preferably 0.35-0.4);

[0019] Preferably, the perovskite substrate has a chemical formula of Sr 0.9 Co x Fe y Ni 1-x-y O 3-δ Perovskite material, wherein x=0.5, y=0.3-0.4;

[0020] In the present invention, the ingredients are prepared according to the chemically measured ratio, and the ingredients are subjected to complexation reaction with the complexing auxiliary agent to obtain the gel.

[0021] In the present invention, the complexing aid includes at least one of citric acid, oxalic acid and stearic acid;

[0022] In the present invention, the complexing aid further comprises at least one auxiliary agent selected from ethylenediaminetetraacetic acid, glucose and tartaric acid. In the present invention, the amount of the auxiliary agent can be adjusted as required, for example, the molar content of the auxiliary agent in the complexing aid is less than or equal to 50 mol%, and further can be 20 to 50 mol%.

[0023] In the present invention, the ratio of the complexing aid to the total metal molar amount of AB can be adjusted as needed, and considering the processing cost, it can be further 1 to 5:1, and further 2 to 3:1.

[0024] In the present invention, the temperature in the sol-gel reaction stage is 60-95° C., and the pH is 8-9.5.

[0025] Preferably, the temperature in the foaming and aging stage is 150-250°C, more preferably 180-200°C.

[0026] There is no particular requirement for the foaming and aging time as long as a dry gel is formed. For example, the time may be more than 1 hour, and may further be 5 to 20 hours in consideration of the processing efficiency.

[0027] In the present invention, the oxidation calcination stage is carried out in an oxygen-containing atmosphere. The oxygen volume content of the oxygen-containing atmosphere is, for example, not less than 5%; in consideration of the processing cost, it may further be air.

[0028] Preferably, the temperature of the oxidation calcination is 900 to 1100° C., and further can be 950 to 1050° C.;

[0029] In the present invention, the duration of the oxidation calcination stage can be determined according to the formation of perovskite, and the duration can be more than 1 hour. Considering the processing efficiency, the duration can be further 4 to 8 hours. Considering the processing efficiency, the duration can be further 4 to 6 hours.

[0030] In the present invention, the hydrogen-containing atmosphere is a composite gas of hydrogen and protective gas;

[0031] Preferably, the protective gas is at least one of nitrogen and an inert gas, such as Ar.

[0032] Preferably, the volume content of hydrogen in the hydrogen-containing atmosphere is 5 to 25 v%, preferably 10 to 15 v%;

[0033] The present invention has found that innovatively calcining the A-defect perovskite in a hydrogen-containing atmosphere and further coordinating the temperature control can unexpectedly achieve synergy, allowing it to precipitate cobalt-iron-nickel ternary alloy nanoparticles at this temperature, and improve its in-situ distribution state and chemical bonding ability with the substrate, thereby improving the OER activity and catalytic stability of the material.

[0034] In the present invention, the flow rate of the hydrogen-containing atmosphere is 15 to 25 mL / min, and can be further 18 to 22 mL / min in consideration of treatment effect and cost.

[0035] In the present invention, the combined control of the calcination temperature is the key to unexpectedly forming in-situ precipitated ternary alloy particles at low temperature and improving the OER performance.

[0036] Preferably, the calcination temperature is 350-400° C., more preferably 350-360° C. Studies have found that under the preferred conditions, the OER performance of the prepared material can be further synergistically improved.

[0037] Preferably, the calcination time is 0.5 to 5 hours, more preferably 1 to 2 hours.

[0038] The present invention also provides a perovskite-based composite catalyst prepared by the preparation method and loaded with cobalt-iron-nickel ternary alloy nanoparticles by in-situ precipitation.

[0039] The special preparation method described in the present invention can give the prepared material special physical, chemical and structural characteristics, and the material with special characteristics prepared by the preparation method has unexpected effects in OER catalysis.

[0040] In the present invention, the perovskite-based composite catalyst comprises a perovskite substrate and in-situ desolvated Co-Fe-Ni ternary alloy nanoparticles (also referred to as alloy nanoparticles in the present invention);

[0041] The perovskite substrate is a perovskite material after the A-site defect and the B-site desolvation and precipitation of the alloy nanoparticles, and its expression is A 1-x B y O 3-δ , wherein A is an alkaline earth or rare earth metal element, B includes Co, Fe and Ni, 0.85≤x<1, 0<y<1, δ represents the number of oxygen lattice defects;

[0042] The alloy nanoparticles are Co-Fe-Ni ternary alloy particles.

[0043] The present invention provides a new perovskite-based composite catalyst, which takes a single perovskite structure material with an A-site defect as a substrate, and innovatively combines it with Co-Fe-Ni ternary synergistic alloy particles precipitated by in-situ precipitation on the surface. Based on the combined control of the substrate, the ternary alloy and the in-situ structure, synergy can be achieved to improve the OER activity and catalytic stability of the material.

[0044] In the present invention, the synergy of the A-site defect characteristics of the substrate, the Co-Fe-Ni ternary alloy and its in-situ precipitation loading structure is the key to improving its OER activity and catalytic stability.

[0045] In the present invention, the Co-Fe-Ni ternary alloy nanoparticles are dispersed on the surface of the perovskite substrate. In addition, the present invention also found that the catalyst prepared by the preparation method, the Co-Fe-Ni ternary alloy nanoparticles and the perovskite matrix form a unique "nested" structure, the interaction between the nanoparticles and the perovskite is strong, and it is not easy to agglomerate, which is conducive to improving the stability of the catalyst system. In addition, the preparation method can simultaneously realize the construction of solid defects and composite interfaces, and the heterogeneous structure interface composed of nanoparticles and perovskites can effectively improve the surface electronic environment, accelerate charge transfer and material transfer in the catalytic process, and effectively improve the oxygen evolution performance.

[0046] Preferably, the perovskite substrate has a block structure with an average size of about 0.5-0.7 μm, and the alloy nanoparticles have an average particle size of about 50-100 nm.

[0047] The present invention also provides an application of the perovskite-based composite catalyst as an OER catalyst; preferably, the perovskite-based composite catalyst is used as an OER catalyst for electrolyzing water to produce oxygen.

[0048] The present invention has found that the innovative use of the new perovskite-based composite catalyst as an OER catalytic material can exhibit excellent OER catalytic activity and catalytic stability, and further using it in water electrolysis for oxygen evolution can obtain good preparation effects.

[0049] The present invention also provides an anode catalyst for oxygen evolution by electrolysis of water, which comprises a current collector and an anode material composited on the current collector, wherein the anode material comprises an active material, a conductive agent and a binder, wherein the active material comprises the perovskite-based composite catalyst.

[0050] The anode catalyst of the present invention, in addition to comprising the perovskite-based composite catalyst of the present invention, may have other ingredients and component structures that are well known in the industry.

[0051] The present invention also provides a water electrolysis device, which comprises an anode catalyst of the perovskite-based composite catalyst described in the present invention.

[0052] The water electrolysis device of the present invention, in addition to comprising the perovskite-based composite catalyst of the present invention, may have other materials and structural components that are well known in the industry.

[0053] Beneficial effects:

[0054] (1) The present invention also provides a method for preparing a perovskite-based composite catalyst, which is based on the combined control of the single perovskite with A-site defects and the roasting temperature under a hydrogen-containing atmosphere, so that synergy can be achieved. At the temperature, the in-situ precipitation of Co-Fe-Ni ternary alloy particles can be achieved, thereby improving the precipitation distribution and the bonding morphology with the substrate. Not only that, a large number of active sites and oxygen vacancies can also be introduced, thereby effectively improving the OER activity and stability of the prepared material.

[0055] (2): The preparation method described in the present invention can prepare a new catalyst with special physical, chemical and structural characteristics, and the catalyst with a special structure prepared by the preparation method has excellent OER activity and catalytic stability.

[0056] (3): The present invention innovatively uses the perovskite-based composite catalyst as an OER catalyst, and further uses it for electrolysis of water for oxygen evolution, which can show excellent activity and catalytic stability. For example, at 10 mA / cm 2 Under the condition of low overvoltage, the overpotential is 280-290mV. The overpotential of the modified perovskite does not change significantly during the 10-hour chronopotentiometry test, showing good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is the XRD diagram of the catalyst prepared in step 2 of Examples 1 to 4, wherein part (a) is the X-ray diffraction spectrum of the perovskite-based catalysts obtained in Example 1, Example 2, Example 3 and Example 4, respectively; (b) is the enlarged X-ray diffraction spectrum of the perovskite-based catalysts obtained in Example 1, Example 2, Example 3 and Example 4 at 43° to 53°.

[0058] Figure 2 1 to 4, wherein part (a) is the X-ray diffraction pattern of the perovskite-based catalysts obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4; part (b) is the X-ray diffraction magnified pattern of the perovskite-based catalysts obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 at 43° to 53°.

[0059] Figure 3The figures are SEM images of the catalysts obtained in Examples 1 to 4 and Comparative Examples 1 to 4, wherein (a) shows a scanning electron microscope image of the perovskite-based composite catalyst with in-situ desolvation of cobalt-iron-nickel ternary alloy nanoparticles on the surface obtained in Example 1. (b) shows a scanning electron microscope image of the perovskite-based composite catalyst with in-situ desolvation of cobalt-iron-nickel ternary alloy nanoparticles on the surface obtained in Example 2. (c) shows a scanning electron microscope image of the perovskite-based composite catalyst with in-situ desolvation of cobalt-iron-nickel ternary alloy nanoparticles on the surface obtained in Example 3. (d) shows a scanning electron microscope image of the perovskite-based composite catalyst with in-situ desolvation of cobalt-iron-nickel ternary alloy nanoparticles on the surface obtained in Example 4. (e) shows a scanning electron microscope image of the Sr obtained in Comparative Example 1. 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ SEM images of perovskite precursors. (f) The figure shows a SEM image of the cobalt-iron-nickel ternary alloy nanoparticles wet-impregnated composite perovskite catalyst obtained in Comparative Example 2. (g) The figure shows a SEM image of the perovskite-based catalyst obtained in Comparative Example 3. (h) The figure shows a SEM image of the perovskite-based catalyst obtained in Comparative Example 4.

[0060] Figure 4 These are transmission electron microscopy analysis images of the perovskite-based composite catalyst with surface in-situ desolvated cobalt-iron-nickel ternary alloy nanoparticles obtained in Example 1, wherein (a) shows a transmission electron microscopy image of the perovskite-based composite catalyst with surface in-situ desolvated cobalt-iron-nickel ternary alloy nanoparticles; (b) shows a high-resolution transmission electron microscopy image of a specified area; (c) shows a selected area electron diffraction image of the perovskite matrix; and (d) shows a selected area electron diffraction image of the alloy particle area.

[0061] Figure 5 It is a high-angle annular dark field image (HAADF) of the perovskite-based composite catalyst of the surface in-situ desolvated cobalt-iron-nickel ternary alloy nanoparticles obtained in Example 1 and the EDS element distribution map of Sr, Co, Fe, Ni and O.

[0062] Figure 6 This is a performance comparison chart of the perovskite-based catalysts obtained in Example 1, Example 2, Example 3 and Example 4.

[0063] Figure 7 This is a performance comparison chart of the perovskite-based catalysts obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4.

[0064] Figure 8 LSV curves of the perovskite-based catalysts obtained in Example 1 and Comparative Example 1 before and after 1000 cycles of CV. DETAILED DESCRIPTION

[0065] The technical solution of the present invention is further described below in conjunction with specific embodiments and accompanying drawings.

[0066] The perovskite-based composite catalyst of the present invention is prepared by using a single perovskite structure precursor material (A 1- x BO 3-δ ) is prepared by calcining in a hydrogen-containing atmosphere at a temperature of 340 to 410°C.

[0067] In the present invention, the single perovskite structure precursor material is a single perovskite structure material of any A metal with A defects and B containing Co, Fe and Ni. That is, the perovskite material satisfying the A-site defect and containing Co, Fe and Ni at the B-site can be used as a precursor material and combined with the calcination conditions of the hydrogen-containing atmosphere described in the present application to prepare a new OER catalytic material with in-situ precipitation of Co, Fe and Ni ternary alloy particles.

[0068] In the present invention, there is no special requirement for the metal element A, which may be an alkaline earth metal or a rare earth. In the present invention, A is typically Sr.

[0069] For example, in the present invention, the precursor material may further be Sr 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ Perovskite: In the present invention, the perovskite precursor material can be prepared based on a known method, for example, a sol-gel method.

[0070] A typical method for preparing a perovskite-based composite catalyst of the present invention includes the following steps, for example:

[0071] Step 1, Sr 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ Preparation of perovskite catalysts

[0072] Synthesis of perovskite catalyst Sr by sol-gel method 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ Powder, where δ represents Sr 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ The number of oxygen lattice defects in an oxide.

[0073] Step 2,

[0074] Sr 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ The perovskite powder is placed in a tubular furnace and calcined in a reducing atmosphere at a temperature of 340 to 410° C. to obtain the modified perovskite.

[0075] In the step 1, the perovskite catalyst Sr is synthesized by a sol-gel method. 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ The oxide powder is prepared by the following steps: a certain amount of metal nitrates of strontium, cobalt, iron and nickel are dissolved in deionized water according to the stoichiometric ratio in the chemical formula to obtain an aqueous solution of metal salt ions, which is stirred at a constant temperature of 60 to 70°C in a magnetic stirrer. Subsequently, ethylenediaminetetraacetic acid and citric acid are mixed to form a complexing agent and added to the solution. Subsequently, ammonia water is slowly added with a dropper to adjust the pH value of the solution to 8 to 9, and the temperature is increased to 80 to 90°C and heated and stirred at a constant temperature until the mixture becomes a reddish-brown gel. The obtained gel is moved to an oven at 150 to 250°C and dried overnight until the gel becomes a black sponge-like porous loose solid. The obtained solid is placed in a mortar and ground into a uniform and fine powder, which is then moved to a muffle furnace for calcination to obtain Sr 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ Perovskite catalyst powder.

[0076] In step 1, the metal nitrates of strontium, cobalt, iron and nickel are respectively Sr(NO3)2, Co(NO3)2·6H2O, Fe(NO3)3·9H2O and Ni(NO3)2·6H2O, and can be prepared according to the stoichiometric ratio, for example, the molar ratio of Sr, Co, Fe and Ni is 0.9:0.5:0.35:0.15. In the present invention, the total amount of elements can be adjusted according to the preparation scale. For example, the following case can be a laboratory scale, and the total number of metal ions can be 0.01-0.1 mol, and further can be 0.02 mol.

[0077] In step 1, the molar ratio of metal ions in the solution: ethylenediaminetetraacetic acid: citric acid monohydrate is 1:1-2:1-2, and the amount of ethylenediaminetetraacetic acid added is 0.02 mol.

[0078] In step 1, the calcination treatment is performed at a heating rate of 2 to 5°C / min, a calcination temperature of 900 to 1000°C, a calcination time of 4 to 5 hours, and a cooling rate of 2 to 5°C / min.

[0079] In step 2, the reducing atmosphere during the calcination process is 10-15v% H2 / Ar.

[0080] In step 2, the calcination treatment is performed at a heating rate of 1 to 10°C / min, a thermal reduction temperature of 350 to 400°C, a reduction time of 1 to 2 hours, and a cooling rate of 1 to 10°C / min.

[0081] The preparation method of the present invention can precipitate Co-Fe-Ni ternary alloy particles in situ at the temperature. For example, the material prepared by the above typical preparation method includes Sr 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ The substrate formed by in-situ desolvation of the B site in the perovskite and the Co-Fe-Ni ternary alloy nanoparticles dispersed on the surface of the substrate. The composition of the ternary alloy nanoparticles is CoFeNi, and δ represents Sr 0.9 Co 0.5 Fe 0.5-x Ni x O 3-δ The number of oxygen lattice defects in the oxide (non-artificially controlled factor).

[0082] The process described in the present invention prepares a composite catalyst material suitable for OER reaction. According to electrochemical performance tests, the composite catalyst prepared by the in-situ desolvation method in the present invention has spontaneous lattice distortion to expose more active sites, which can significantly reduce the overpotential required for electrochemical decomposition of water to produce hydrogen, thereby reducing the energy consumption of water decomposition, and effectively achieving the advantages of low cost, simple process, high catalytic activity and high stability.

[0083] According to the above steps, a perovskite-based composite catalyst with surface in-situ desolvation of cobalt, iron, and nickel ternary alloy nanoparticles was prepared at 10 mA / cm 2 Under the condition of low overvoltage, the overpotential is 280-290mV. The overpotential of the modified perovskite does not change significantly during the 10-hour chronopotentiometry test, showing good stability.

[0084] In the following cases, the overnight time refers to 6 to 12 hours.

[0085] Example 1

[0086] A method for preparing a perovskite-based composite catalyst with in-situ surface desolvation of cobalt, iron, and nickel ternary alloy nanoparticles, the steps of which are as follows:

[0087] Step 1: Sr 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ Preparation of (precursor):

[0088] (1) According to the stoichiometric ratio in the chemical formula (the molar ratio of Sr: Co: Fe: Ni is 0.9: 0.5: 0.35: 0.15), a total molar amount of 0.02 mol of Sr(NO3)2, Co(NO3)2·6H2O, Fe(NO3)3·9H2O and Ni(NO3)2·6H2O was dissolved in 100 mL of deionized water to obtain an aqueous solution of metal salt ions, which was stirred at a constant temperature of 60 to 70° C. in a magnetic stirrer. Subsequently, 0.02 mol of ethylenediaminetetraacetic acid and 0.03 mol of citric acid were mixed to prepare a complexing agent and added to the solution.

[0089] (2) Slowly add ammonia water to the solution obtained in (1) with a dropper, adjust the pH value of the solution to 8-9, raise the temperature to 80-90°C, heat and stir at a constant temperature until the mixed solution turns into a reddish brown gel. Move the obtained gel to an oven at 180-200°C and dry overnight until the gel turns into a black sponge-like porous loose solid.

[0090] (3) The solid obtained in (2) was ground into a uniform fine powder in a mortar, and then moved to a muffle furnace for calcination, and the temperature was raised to 1000°C at a rate of 2°C / min and kept for 5 hours. After cooling, the solid was taken out and ground to obtain Sr with good crystallinity. 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ Perovskite catalyst powder.

[0091] Step 2:

[0092] The Sr prepared by the method described in 1 was treated by in-situ dissolution method. 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ Perovskite powder is modified by adding Sr 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ The perovskite powder was placed in a tubular furnace and calcined at 350°C (marked as T) for 1 hour in a 10% H2 / Ar atmosphere with a gas flow rate of 20 mL / min to obtain a perovskite-based composite catalyst with in-situ desolvated cobalt-iron-nickel ternary alloy nanoparticles on the surface.

[0093] Example 2

[0094] Compared with Example 1, the only difference is that the temperature T in step 2 is 400° C., and other operations and parameters are the same as Example 1.

[0095] Example 3

[0096] Compared with Example 1, the only difference is that the ratio of element A is changed, and the chemical formula of the designed precursor is Sr 0.95 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ , other operations and parameters are the same as in Example 1.

[0097] Example 4

[0098] Compared with Example 1, the only difference is that the ratio of the elements in B is changed, and the chemical formula of the designed precursor is Sr 0.9 Co 0.5 Fe 0.4 Ni 0.1 O 3-δ , other operations and parameters are the same as in Example 1.

[0099] Comparative Example 1

[0100] Compared with Example 1, the only difference is that the hydrogen roasting treatment in step 2 is not performed, and the other operations and parameters are the same as in Example 1, that is, the Sr prepared in step 1 is 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ Perovskite catalysts as OER catalysts.

[0101] Comparative Example 2

[0102] A method for preparing a catalyst of a cobalt-iron-nickel ternary alloy nanoparticle composite perovskite is prepared by a wet impregnation method, and the steps are as follows:

[0103] 1. Dissolve 1 mmol of Co(NO3)2·6H2O, Fe(NO3)3·9H2O and Ni(NO3)2·6H2O in 10 mL of deionized water, then add 10 mmol of SCFN powder (Sr prepared in step 1 of Example 1) 0.9 Co 0.5 Fe 0.35 Ni 0.15 O 3-δ precursor).

[0104] 2. After stirring on a magnetic stirrer for 24 hours at room temperature, the sample was dried in a vacuum drying oven.

[0105] 3. Finally, calcine at 600°C in air atmosphere for 1 hour to obtain the catalyst.

[0106] Comparative Example 3-Precursor is non-A defect material

[0107] Compared with Example 1, the only difference is that the material without A-site defect is formed, that is, the chemical formula of the designed precursor is SrCo 0.5 Fe 0.35 Ni 0.15 O 3-δ : Other operations and parameters are the same as in Example 1.

[0108] Comparative Example 4

[0109] Compared with Example 1, the only difference is that the temperature T in step 2 is 300° C., and other operations and parameters are the same as in Example 1.

[0110] Figure 1 (ad) in the figure respectively show the X-ray diffraction patterns of the perovskite-based catalysts prepared in Examples 1 to 4. It can be found from the patterns that after calcination, a pure perovskite phase material containing a CoFeNi alloy phase is obtained.

[0111] In order to test the oxygen evolution catalytic technical effect of the catalyst prepared by the above-mentioned method for preparing the perovskite-based composite catalyst with in-situ surface desolvation of cobalt-iron-nickel ternary alloy nanoparticles, the following test example was set up.

[0112] The test steps are as follows:

[0113] 1. Preparation of test ink: 5 mg of catalyst sample and 5 mg of Super P Li were weighed and dispersed in 1 mL of anhydrous ethanol for 8 samples of Examples 1 to 4 and Comparative Examples 1 to 4, and mixed evenly. Another 50 μL of Nafion solution was added dropwise to the mixed solution with ethanol as solvent, and ultrasonically vibrated for 1.5 h to form a uniform catalyst ink.

[0114] 2. Take 10 μL of the catalyst ink and apply it to the polished surface of 0.196 cm 2 The center of the glassy carbon electrode was placed in the air and dried naturally into a black uniform film to obtain a working electrode. The working electrode was moved to the electrolyte for electrochemical measurement. The catalyst loading was 0.243 mg cm -2 .

[0115] 3. The electrochemical performance of the catalyst was measured at room temperature using a conventional three-electrode system. The glassy carbon electrode modified with the catalyst ink was used as the working electrode, the Hg / HgO (1.0 M KOH) electrode was used as the reference electrode, the platinum electrode was used as the counter electrode, and the electrolyte was an O2-saturated 1.0 M KOH solution. The linear sweep voltammetry test was performed in the 0.2-1.0 V potential window with a scan rate of 5 mV s -1 , the current density is 10mA / cm 2 The accelerated durability test is based on 100mV s -1 The scan rate was CV cycled 1000 times in the voltage range of 0.2 to 1.0 V, and finally the linear sweep voltammetry test was performed again to compare the changes in overpotential before and after the cycle.

[0116] Table 1 Overpotential test results of samples obtained from Examples 1-4 and Comparative Examples 1-4 as oxygen evolution catalysts

[0117]

[0118] like Figure 1 and Figure 2 As shown, all catalysts show a cubic perovskite structure containing a Pm-3m space group. After reduction at 340-410°C (preferably 350-400°C) in a 10% H2 / Ar atmosphere for 1 h, the characteristic peaks of the perovskite shift to a low angle, indicating lattice expansion, which may be caused by the regulation of oxygen vacancies or lattice distortion after SCFN desolvation. In addition, it can be found from the XRD spectra of Example 1, Example 2, Example 3, Example 4 and Comparative Example 2 that two new peaks appear at ~45° and ~52°. This can be attributed to the presence of CoFeNi alloy, confirming the desolvation of metal nanoparticles after thermal reduction. No new peaks were found in the XRD spectra of Comparative Example 3 and Comparative Example 4, indicating that the preparation conditions cannot desolvate nano alloy particles in situ.

[0119] like Figure 3 As shown, a large number of spherical nanoparticles are evenly dispersed on the surface of the perovskite-based composite catalysts obtained in Example 1, Example 2, Example 3 and Example 4, while the surface of Comparative Example 1 is smooth. This shows that the preparation method of the present invention can dissolve a large number of nanoparticles from the perovskite matrix. Some irregular blocks of different sizes appeared on the surface of Comparative Example 2, which had a clear boundary with the matrix perovskite, indicating that the interaction between the two phases of the composite material prepared by the wet impregnation method is not as strong as that prepared by the dissolution method. There is no nanoparticle distribution on the surface of Comparative Example 3 and Comparative Example 4, indicating that it is impossible to obtain a perovskite-based composite catalyst with dispersed nano-alloy particles on the surface under the preparation conditions.

[0120] like Figure 4As shown, the transmission electron microscopy analysis picture of the perovskite-based composite catalyst with surface in-situ desolvation of cobalt-iron-nickel ternary alloy nanoparticles obtained in Example 1 shows that the perovskite-based composite catalyst with surface in-situ desolvation of cobalt-iron-nickel ternary alloy nanoparticles was successfully prepared.

[0121] like Figure 5 As shown, the high-angle annular dark field image (HAADF) of the perovskite-based composite catalyst with surface in-situ desolvation of cobalt-iron-nickel ternary alloy nanoparticles obtained in Example 1 and the EDS element distribution map of Sr, Co, Fe, Ni and O. From the figure, it can be clearly observed that the high-concentration Co, Fe and Ni aggregation area, and there is no other element distribution in this area, indicating the precipitation of cobalt-iron-nickel ternary alloy nanoparticles.

[0122] like Figure 6 As shown in Table 1, it can be concluded that at a current density of 10 mA / cm 2 When, the overpotentials of Example 1, Example 2, Example 3 and Example 4 are all less than those of Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4, indicating that the perovskite-based composite catalyst of the surface in-situ precipitation of cobalt-iron-nickel ternary alloy nanoparticles has a more excellent oxygen evolution reaction catalytic performance, and the advantage is more significant. In addition, Example 1, Example 2, Example 3 and Example 4 all have smaller Tafel slope values, indicating that the perovskite-based composite catalyst of the surface in-situ precipitation of cobalt-iron-nickel ternary alloy nanoparticles has good OER reaction kinetics. After 1000 CV cycle scans, the overpotential changes of Example 1, Example 2, Example 3 and Example 4 are all less than those of Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4, indicating that the perovskite-based composite catalyst of the surface in-situ precipitation of cobalt-iron-nickel ternary alloy nanoparticles has good cycle stability. The product obtained by the preparation method of the perovskite-based composite catalyst of the surface in-situ precipitation of cobalt-iron-nickel ternary alloy nanoparticles disclosed by the present invention has good commercial value as an electrocatalyst in the field of electrolytic water oxygen evolution reaction.

[0123] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be achieved by other skilled in the art through creative labor shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a perovskite-based composite catalyst with in-situ surface desolvation of cobalt, iron, and nickel ternary alloy nanoparticles, characterized in that: The expression for obtaining the A-site defect is A 1-x BO 3-δ The perovskite precursor material is then calcined in a hydrogen atmosphere at a temperature of 340 to 410° C. to obtain; The A 1-x BO 3-δ In which, A is an alkaline earth or rare earth metal element, B includes Co, Fe and Ni, and 0.85≤x<1.

2. The preparation method according to claim 1, characterized in that The perovskite precursor material is prepared by a sol-gel method, the steps of which are: mixing stoichiometric source A, source B and a complexing agent to carry out a sol-gel reaction, then foaming and aging to obtain a dry gel, and then performing an oxidative calcination treatment to obtain the perovskite precursor material.

3. The preparation method according to claim 2, characterized in that: The A source is a water-soluble salt of metal A, preferably at least one of nitrate, sulfate, chloride and acetate of metal A; Preferably, the A metal is Sr; Preferably, x is 0.9 to 0.95; Preferably, the B source is a water-soluble salt of B metal, preferably at least one of nitrate, metal alkoxide, chloride and acetate of B metal; Preferably, in the B metal element, the molar ratio of Co, Fe and Ni is x:y:(1-xy), wherein x is 0.45-0.55: y is 0.3-0.4; Preferably, the perovskite substrate has a chemical formula of Sr 0.9 Co x Fe y Ni 1-x-y O 3-δ Perovskite material, wherein x=0.5, y=0.3-0.4; Preferably, the complexing aid includes at least one of citric acid, oxalic acid, and stearic acid; Preferably, the complexing aid further comprises at least one of ethylenediaminetetraacetic acid, glucose and tartaric acid; Preferably, the ratio of the complexing aid to the total metal molar amount of AB is 1 to 5:1, further 2 to 3:

1.

4. The preparation method according to claim 2, characterized in that: The temperature in the sol-gel reaction stage is 60-95°C and the pH is 8-9.5; Preferably, the temperature in the foaming and aging stage is 150-250°C; Preferably, the oxidation calcination stage is carried out in an oxygen-containing atmosphere; Preferably, the oxygen content of the oxygen-containing atmosphere is not less than 5% by volume; Preferably, the temperature of oxidation calcination is 900-1100°C; Preferably, the oxidation calcination stage lasts for 4 to 8 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The hydrogen-containing atmosphere is a composite gas of hydrogen and protective gas; Preferably, the protective gas is at least one of nitrogen and an inert gas; Preferably, the volume content of hydrogen in the hydrogen-containing atmosphere is 5 to 25 v%, preferably 10 to 15 v%; Preferably, the flow rate of the hydrogen-containing atmosphere is 15 to 25 mL / min; Preferably, the calcination time is 0.5 to 5 hours, preferably 1 to 2 hours.

6. A perovskite-based composite catalyst loaded with cobalt-iron-nickel ternary alloy nanoparticles by in-situ precipitation prepared by the preparation method according to any one of claims 1 to 5; characterized in that: The invention comprises a perovskite substrate formed by in-situ desolvation in a perovskite precursor material and Co-Fe-Ni ternary alloy nanoparticles in-situ composited on the surface of the perovskite substrate.

7. The perovskite-based composite catalyst with in-situ surface desolvation of cobalt, iron, and nickel ternary alloy nanoparticles as claimed in claim 6, characterized in that: The Co-Fe-Ni ternary alloy nanoparticles are dispersed on the surface of the perovskite substrate; Preferably, the perovskite substrate has a block structure with an average size of about 0.5-0.7 μm, and the particle size of the Co-Fe-Ni ternary alloy nanoparticles is an average size of about 50-100 nm.

8. Use of a perovskite-based composite catalyst prepared by the preparation method according to any one of claims 1 to 5, characterized in that: Use it as an OER catalyst; Preferably, it is used as an OER catalyst for electrolysis of water to produce oxygen.

9. An anode catalyst for oxygen evolution in water electrolysis, characterized in that: The active material comprises a perovskite-based composite catalyst prepared by the preparation method according to any one of claims 1 to 5.

10. A water electrolysis device, characterized in that: It comprises the anode catalyst according to claim 9.

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