CN116581314A - High-entropy oxide catalyst for fuel cell and preparation method thereof - Google Patents
High-entropy oxide catalyst for fuel cell and preparation method thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 76
- 239000000446 fuel Substances 0.000 title claims abstract description 30
- 238000002360 preparation method Methods 0.000 title abstract description 27
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 28
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000001301 oxygen Substances 0.000 claims abstract description 15
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 15
- 239000000126 substance Substances 0.000 claims abstract description 15
- 239000013078 crystal Substances 0.000 claims abstract description 12
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 9
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 31
- 238000010438 heat treatment Methods 0.000 claims description 29
- 239000011259 mixed solution Substances 0.000 claims description 24
- 238000000137 annealing Methods 0.000 claims description 22
- 239000000843 powder Substances 0.000 claims description 21
- 239000000243 solution Substances 0.000 claims description 19
- 239000012298 atmosphere Substances 0.000 claims description 16
- 239000007787 solid Substances 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 14
- 238000005245 sintering Methods 0.000 claims description 14
- 229910052802 copper Inorganic materials 0.000 claims description 13
- 238000001816 cooling Methods 0.000 claims description 12
- 238000000227 grinding Methods 0.000 claims description 11
- 238000003837 high-temperature calcination Methods 0.000 claims description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims description 11
- 239000001257 hydrogen Substances 0.000 claims description 10
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 9
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 8
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 7
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 7
- 230000001105 regulatory effect Effects 0.000 claims description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 5
- 239000008367 deionised water Substances 0.000 claims description 5
- 229910021641 deionized water Inorganic materials 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 4
- 229910001960 metal nitrate Inorganic materials 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 claims description 2
- 238000005303 weighing Methods 0.000 claims description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 abstract description 40
- 229910021529 ammonia Inorganic materials 0.000 abstract description 20
- 230000003197 catalytic effect Effects 0.000 abstract description 16
- 238000012360 testing method Methods 0.000 abstract description 12
- 229910052733 gallium Inorganic materials 0.000 abstract description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 68
- 239000010949 copper Substances 0.000 description 44
- 239000011572 manganese Substances 0.000 description 40
- 230000000052 comparative effect Effects 0.000 description 35
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 34
- 229910052712 strontium Inorganic materials 0.000 description 17
- 238000006243 chemical reaction Methods 0.000 description 15
- 239000011575 calcium Substances 0.000 description 13
- 229910052748 manganese Inorganic materials 0.000 description 13
- 239000010936 titanium Substances 0.000 description 13
- 239000011651 chromium Substances 0.000 description 12
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 10
- 229910052746 lanthanum Inorganic materials 0.000 description 10
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 10
- 229910017052 cobalt Inorganic materials 0.000 description 9
- 239000010941 cobalt Substances 0.000 description 9
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 9
- 239000000463 material Substances 0.000 description 9
- 239000011701 zinc Substances 0.000 description 9
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 8
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 8
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 8
- 229910002651 NO3 Inorganic materials 0.000 description 7
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 7
- 229960004106 citric acid Drugs 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 239000010406 cathode material Substances 0.000 description 4
- 230000005012 migration Effects 0.000 description 4
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- 230000004048 modification Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 239000002243 precursor Substances 0.000 description 4
- 229910052719 titanium Inorganic materials 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000001354 calcination Methods 0.000 description 3
- 239000012018 catalyst precursor Substances 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 238000000840 electrochemical analysis Methods 0.000 description 3
- 239000012299 nitrogen atmosphere Substances 0.000 description 3
- 125000004430 oxygen atom Chemical group O* 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical compound [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 150000001242 acetic acid derivatives Chemical class 0.000 description 2
- 230000004075 alteration Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229960004543 anhydrous citric acid Drugs 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000002484 cyclic voltammetry Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical compound Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- 229920000557 Nafion® Polymers 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 159000000021 acetate salts Chemical class 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000007809 chemical reaction catalyst Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- -1 citrate ions Chemical class 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010668 complexation reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 239000011224 oxide ceramic Substances 0.000 description 1
- 229910052574 oxide ceramic Inorganic materials 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/88—Processes of manufacture
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Abstract
The invention discloses a high entropy oxide catalyst for fuel cells and a preparation method thereof, wherein the chemical formula of the high entropy oxide catalyst is as follows:wherein A is at least one of Ca, sr and Ba, B is at least five of Ni, cu, fe, co, mn, zn, cr, ti, al and Ga, the molar ratio of the elements in B is 0.6-1.7, x is 0.075-0.925, n is 2 or 3, the crystal structure of the high-entropy oxide catalyst is Ruddlesden-pop type, delta is oxygen vacancy content, and the delta satisfies the following relation:，. The invention providesThe high-entropy oxide catalyst has good catalytic performance in low temperature, room temperature and other environments, has simple preparation process, low cost, good repeated test and wide application prospect, and can be applied to ammonia fuel cells.
Description
Technical Field
The invention belongs to the technical field of fuel cells, and particularly relates to a high-entropy oxide catalyst for a fuel cell and a preparation method thereof.
Background
Ammonia energy (NH) 3 ) As a hydrogen-rich carbon-free clean energy source, the method is a hydrogen storage medium with great potential, a mature industrial system lays a deep foundation for long-period and large-scale storage and transportation of hydrogen energy, and the popularization of ammonia energy has great significance for modeling a new global energy development pattern. Based on a zero-carbon energy system, the source of ammonia is very wide, and the ammonia can be directly used for generating electricity by an ammonia fuel cell without generating greenhouse gases no matter whether green ammonia synthesized by the electrolysis of renewable energy sources or ammonia-containing wastewater discharged in daily production and life, so that a powerful support is provided for realizing the aim of double carbon.
As in patent CN114709433a, a nitrogen-doped carbon-supported Pt metal catalyst for electrocatalytic oxidation of ammonia, and a preparation method and application thereof are provided, the catalyst comprising an active component and a carrier, the active component being Pt, the carrier being nitrogen-doped carbon; the preparation method comprises the steps of taking silicon dioxide as a template, taking formaldehyde and melamine as carbon and nitrogen sources respectively, carrying out high-temperature pyrolysis, etching by hydrogen fluoride to obtain nitrogen-doped hollow porous carbon spheres, adopting a dipping reduction method, taking sodium borohydride as a reducing agent, and reducing a precursor of Pt under intense stirring at room temperature to synthesize the Pt/N-C catalyst. The scheme provides a preparation method of the nitrogen-doped carbon-supported Pt catalyst, and has a good application prospect in an alkaline membrane direct ammonia fuel cell.
However, the ammonia oxidation reaction catalyst related to the power generation of the ammonia fuel cell has the problems of complex preparation process, high cost, slow reaction kinetics and the like.
Since the introduction of the concept of higher building entropy into the field of oxide ceramics, there has been a study on the application of Ruddlesden-Popper type layered perovskite structure materials to the cathode of solid oxide fuel cells. For example, patent CN114824303A discloses a cathode material with R-P layered medium entropy perovskite structure and a preparation method thereof, and the molecular formula is La 1.4 Sr 0.6 (Co，Fe，Ni，Mn) 1/4 O 4+δ Wherein δ represents an oxygen vacancy content. The preparation method comprises the following steps: to respectively contain La 3+ 、Sr 2+ 、Co 2+ 、Fe 3+ 、Ni 2+ 、Mn 2+ The compounds of (2) are taken as raw materials, and each is weighed according to the stoichiometric ratio of the corresponding elements in the molecular formulaThe preparation method comprises the steps of (1) raw materials, respectively adding the raw materials into deionized water, stirring, dissolving and uniformly mixing to obtain a solution A; respectively adding citric acid and ethylene glycol into the solution A, heating, stirring, dissolving, transferring into an electric furnace, heating to spontaneous combustion, and continuously heating to form ash to obtain a precursor; and grinding the precursor, and transferring the ground precursor into a horse boiling furnace for heating to obtain cathode powder, namely the R-P type layered medium entropy perovskite structure cathode material. The medium-entropy perovskite structure material disclosed by the patent can only improve the stability and the conductivity of the cathode and reduce the thermal expansion coefficient of the cathode material.
Therefore, how to develop a catalyst for an ammonia fuel cell that is efficient, economical and has industrial conditions in combination with the Ruddlesden-Popper layered perovskite structure is a problem to be solved by those skilled in the art.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a high-entropy oxide catalyst for a fuel cell and a preparation method thereof, wherein the chemical formula of the high-entropy oxide catalyst is as follows:wherein A is at least one of Ca, sr and Ba, B is at least five of Ni, cu, fe, co, mn, zn, cr, ti, al, ga, the molar ratio of the elements in B is 0.6-1.7, x is 0.075-0.925, n is 2 or 3, the crystal structure of the high-entropy oxide catalyst is Ruddlesden-pop type, delta is oxygen vacancy content, and the delta satisfies the following relation:，/>. The high-entropy oxide catalyst provided by the invention has good catalytic performance in low temperature, room temperature and other environments, is simple in preparation process, low in cost, good in repeated test and wide in application prospect, and can be applied to the fields of ammonia fuel cells and electrolytic hydrogen production.
In a first aspect, the present invention provides a high entropy oxide catalyst for a fuel cell, comprising:
the chemical formula of the high entropy oxide catalyst is:wherein A is at least one of Ca, sr and Ba, B is at least five of Ni, cu, fe, co, mn, zn, cr, ti, al, ga, the molar ratio of the elements in B is 0.6-1.7, the value of x is 0.075-0.925, and the value of n is 2 or 3;
the crystal structure of the high-entropy oxide catalyst is Ruddlesden-Popper type, delta is oxygen vacancy content, and the value of delta satisfies the following relationship:，/>。
further, the value of x is 0.25-0.75.
Further, B contains Ni and Cu elements.
In a second aspect, the present invention also provides a method for preparing the high entropy oxide catalyst for fuel cells, comprising the steps of:
weighing metal nitrate or acetate containing elements A and B according to stoichiometric ratio, dissolving in deionized water, and magnetically stirring at room temperature to obtain mixed solution;
adding citric acid and ethylenediamine tetraacetic acid into the mixed solution until the pH value of the mixed solution is 0.5-2, and then regulating the pH value of the mixed solution to 6-8 by using ammonia water to obtain a clear solution;
heating the clarified solution to form gel with a skeleton structure or a grid structure, and sintering the gel at high temperature to prepare solid powder;
and (3) carrying out at least two times of alternate grinding and high-temperature calcination on the solid powder, and then carrying out annealing treatment in an inert atmosphere or a reducing atmosphere, wherein the annealing temperature is 100-600 ℃, the annealing time is 0.5-2 h, and the heating and/or cooling rate of annealing is 1-10 ℃/min.
Further, the ratio of the total molar amount of the metal elements of a and B to the molar amount of citric acid is 1: 1-1: the ratio of the total molar amount of the metal elements of 4, A and B to the molar amount of ethylenediamine tetraacetic acid is 1: 1-1: 5.
further, the clarified solution is heated to form a gel of a skeletal structure or a network structure, specifically:
and heating the clear solution at the heating temperature of 80-160 ℃ for 2-24 hours.
Further, the clarified solution is heated to form a gel of a skeletal structure or a network structure, specifically:
and heating the clear solution at a heating temperature of 90-110 ℃ for 12-20 hours.
Further, the gel is sintered at high temperature, specifically:
and (3) performing high-temperature sintering on the gel at a high-temperature sintering temperature of 320-450 ℃ for 3-6 hours.
Further, the solid powder is subjected to at least two alternating grinding and high-temperature calcination, specifically:
the high-temperature calcination temperature of the solid powder is 500-1200 ℃, the high-temperature calcination time is 2-6 h, and the heating and/or cooling rate of the high-temperature calcination is 1-10 ℃/min.
Further, the annealing treatment is performed in an inert atmosphere or a reducing atmosphere, specifically: the inert atmosphere or the reducing atmosphere is at least one of nitrogen, argon and hydrogen, the annealing temperature is 300-500 ℃, the annealing time is 0.5-1 h, and the heating and/or cooling rate of annealing is 5-10 ℃/min.
The invention provides a high entropy oxide catalyst for a fuel cell and a preparation method thereof, which at least comprise the following beneficial effects:
(1) The high-entropy oxide catalyst provided by the invention combines the high-entropy material with the perovskite layered structure, so that rich and flexible component design can be performed, and the dependence on single element is reduced. Meanwhile, the electronic structure can be regulated and controlled by changing the stoichiometric ratio, so that the catalytic activity is further improved.
(2) The high entropy effect of thermodynamics and the kinetic hysteresis diffusion effect enable the high entropy oxide to maintain stable structure under extreme conditions, and the stability is further enhanced by combining with Ruddlesden-Popper type layered structure.
(3) The multi-metal synergy and the highly disordered and distorted crystal lattice of the high-entropy material are beneficial to migration of electrons and ions, and in the Ruddlesden-Popper type structure, the addition of the perovskite layer (i.e. n) can further expand the three-dimensional attribute, and is beneficial to improving the catalytic activity.
(4) The pH value of the mixed solution is regulated by ammonia water, so that the original acidic system of the mixed solution can be changed, and the phenomena that the ionization of citric acid is inhibited, the complex of citrate ions and metal ions is poor, so that metal nitrate is separated out again, crystals are precipitated at the bottom of a container, high-temperature sintering can not be initiated almost, and meanwhile, the reaction is incomplete and the like are avoided. The pH value range is accurately controlled, the reaction can be ensured to be carried out according to the route of component design, and the full complexation and the complete high-temperature sintering are realized.
(5) The high-entropy oxide catalyst provided by the invention has good catalytic activity at low temperature or even room temperature, and has the advantages of simple preparation process, low cost, good repeated test and wide application prospect, and can be applied to ammonia fuel cells and the field of electrolytic hydrogen production.
Drawings
FIG. 1 is an XRD data pattern for a high entropy oxide catalyst prepared in example 1 provided herein;
FIG. 2 is a SEM image at the 100 μm scale of the high entropy oxide catalyst prepared in example 1 provided by the invention;
FIG. 3 shows the 0.5M KOH+55 mM NH of the catalysts prepared in example 1 and comparative example 7, respectively, provided by the present invention 4 Test graph of ammoxidation reaction in Cl solution.
Detailed Description
In order to better understand the above technical solutions, the following detailed description will be given with reference to the accompanying drawings and specific embodiments. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, the "plurality" generally includes at least two.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a product or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such product or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a commodity or device comprising such element.
Dielectric materials of Ruddlesden-pop type layered perovskite structure are attracting attention due to their advantages of excellent stability, abundant crystal structure, various components, controllable physicochemical properties, and the like. The Ruddlesden-poper type layered perovskite structure compound with different sizes is designed and synthesized by utilizing the structure evolution rule so as to obtain materials with different functions.
The current intermediate entropy oxide cooperates with Ruddlesden-pop er type layered perovskite structure, is easy to synthesize, can improve the stability and conductivity of the cathode, reduces the thermal expansion coefficient of the cathode material, and has limited improvement on catalytic activity.
The high-entropy oxide is a material mainly composed of five or more metal elements in an equimolar ratio or a near molar ratio, is widely applied to the fields of energy conversion, energy storage and the like, and has wide application prospect in the catalysis field due to the characteristics of rich active sites, adjustable specific surface area, stable crystal structure, ingredient customizable and the like.
In order to improve the comprehensive performance of the anode catalyst of the ammonia fuel cell and realize stable application and reduce the requirement on the use environment, a high-entropy material is combined with a Ruddlesden-Popper layered perovskite structure, and a catalyst with excellent catalytic activity and stability is developed and designed. Accordingly, the present invention provides a high entropy oxide catalyst for a fuel cell, comprising: the chemical formula of the high entropy oxide catalyst is:wherein A is at least one of Ca, sr and Ba, B is at least five of Ni, cu, fe, co, mn, zn, cr, ti, al, ga, the molar ratio of the elements in B is 0.6-1.7, the value of x is 0.075-0.925, and the value of n is 2 or 3;
the crystal structure of the high-entropy oxide catalyst is Ruddlesden-Popper type, delta is oxygen vacancy content, and the value of delta satisfies the following relationship:，/>. Delta represents that the crystal structure has oxygen defects, namely oxygen defects caused by oxygen overflow, for example, when n=2, 7 oxygen atoms are required according to the chemical formula, but after doping of an element A, calcining, annealing and other steps in the preparation process, oxygen overflow can be caused, so that the number of oxygen atoms is smaller than 7, and when the value of delta is in the range of 0.35-1.4, the catalytic performance of the prepared high-entropy oxide catalyst is optimal. If the value of-delta exceeds 20% of the number of oxygen atoms, the Ruddlesden-poper crystal structure is unstable, and the structure may collapse.
Preferably, the value of x is 0.25-0.75.
Preferably, B contains Ni and Cu.
The Ruddlesden-Popper type high-entropy oxide catalyst prepared by the method can be coupled or independently applied to ammoxidation (Ammonia Oxidation Reaction, AOR), hydrogen evolution (Hydrogen Evolution Reaction, HER) or oxygen evolution (Oxygen Evolution Reaction, OER), and has good catalytic activity and stability.
The high-entropy oxide catalyst provided by the invention combines the high-entropy concept with the perovskite layered structure, and can be subjected to rich and flexible component design, so that the dependence on single element is reduced, and the electronic structure is regulated and controlled by changing the stoichiometric ratio, so that the catalytic activity is further improved; the high entropy effect of thermodynamics and the kinetic hysteresis diffusion effect enable the high entropy oxide to maintain stable structure under extreme conditions, and the stability of the high entropy oxide is further enhanced by combining with Ruddlesden-Popper layered structure; the highly disordered and distorted lattice of the high entropy material favors the migration of electrons and ions, while in the Ruddlesden-Popper structure, the addition of the perovskite layer (i.e., n) further increases the conductivity of the material.
The high-entropy oxide catalyst provided by the invention has good catalytic activity at low temperature or even room temperature, and has the advantages of simple preparation process, low cost, good repeated test and wide application prospect, and can be applied to ammonia fuel cells and the field of electrolytic hydrogen production.
The following describes the high entropy oxide catalyst of the present invention and the specific preparation process by combining examples and comparative examples:
example 1:
the Ruddlesden-Popper type high entropy oxide catalyst given in this example has the formula: (La) 0.75 Sr 0.25 ) 3 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 ) 2 O 7-δ At this time, A is Sr, B is Ni, cu, fe, co and Mn, the molar amounts of the elements of B are the same, x is 0.25, n is 2, and delta is 0.35-1.4.
The preparation method of the Ruddlesden-pop type high-entropy oxide catalyst specifically comprises the following steps:
according to the chemical formula (La) 0.75 Sr 0.25 ) 3 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 ) 2 O 7-δ Stoichiometric ratio of La, A and B inThe method comprises the steps of determining nitrate containing lanthanum (La), strontium (Sr), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co) and manganese (Mn) respectively, and specifically comprises the following steps:
0.0197 mol of La (NO) 3 ) 3 ·6H 2 O, 0.0066 mol Sr (NO) 3 ) 2 ·4H 2 O, 0.0035 mol of Ni (NO) 3 ) 2 ·6H 2 O, 0.0035 mol of Cu (NO) 3 ) 2 ·3H 2 O, 0.0035 mol of Fe (NO) 3 ) 3 ·9H 2 O, 0.0035 mol of Co (NO) 3 ) 2 ·6H 2 O and 0.0035 mol of Mn (NO 3 ) 2 ·4H 2 O。
The nitrate is dissolved in deionized water, and the uniform mixed solution is obtained by magnetic stirring at room temperature.
Then, anhydrous citric acid and ethylenediamine tetraacetic acid were added to the mixed solution, wherein the ratio of the total molar amount of the metal elements (La, a, B) to the molar amount of citric acid was 1:1.5, the ratio of the total molar amount of the metal elements (La, A, B) to the molar amount of ethylenediamine tetraacetic acid is 1:2, namely adding 0.0525 mol of anhydrous citric acid and 0.0875 mol of ethylenediamine tetraacetic acid in sequence, stirring for 1h to obtain a mixed solution with a pH value of 1.15, then regulating the pH value of the mixed solution to 6 by using ammonia water to obtain a clear solution, and then heating the clear solution at 90 ℃ for 12h to form gel with a framework structure.
And (3) performing high-temperature sintering on the formed framework structure gel, wherein the high-temperature sintering temperature is 400 ℃, and the gel can obtain dry solid powder after high-temperature sintering.
And (3) after the obtained solid powder is cooled to room temperature, fully grinding the solid powder by using a mortar, pouring the powder into a crucible, placing the crucible in a tubular furnace, calcining in an air atmosphere, heating to 350 ℃ at a heating rate of 5 ℃/min, preserving heat for 2 hours, taking out the solid powder after the temperature is reduced to room temperature, and fully grinding the solid powder by using the mortar to obtain the high-entropy oxide catalyst precursor.
And pouring a proper amount of high-entropy oxide catalyst precursor into a crucible, placing the crucible in a tube furnace, calcining in an air atmosphere, heating to 1000 ℃ at a heating rate of 5 ℃/min, preserving heat for 3 hours, and then cooling to room temperature at a cooling rate of 5 ℃/min and taking out.
And pouring a proper amount of the powder fully ground in the steps into a crucible, placing the crucible in a tube furnace, annealing in a nitrogen atmosphere, heating to 500 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, cooling to room temperature at a cooling rate of 5 ℃/min, and taking out to obtain the Ruddlesden-Popper type high-entropy oxide catalyst.
XRD testing was performed on the prepared Ruddlesden-Popper type high entropy oxide catalyst, and SEM images at 100 μm scale were observed.
As shown in fig. 1-2, the high-entropy oxide catalyst has a Ruddlesden-Popper type rhombic phase structure, and the granularity of the high-entropy oxide catalyst is in the micron order through microscopic observation.
Example 2:
on the basis of example 1, example 2 adjusted the following parameters.
The Ruddlesden-Popper type high entropy oxide catalyst given in this example has the formula: (La) 0.75 Ca 0.25 ) 3 (Ni 0.25 Cu 0.15 Fe 0.15 Co 0.15 Mn 0.15 Ti 0.15 ) 2 O 7-δ At this time, a is Ca, B is Ni, cu, fe, co, mn and Ti, and the molar ratio between the elements of B is 5:3:3:3:3:3, wherein the value of x is 0.25, the value of n is 2, and the value of delta is 0.35-1.4.
According to the chemical formula (La) 0.75 Ca 0.25 ) 3 (Ni 0.25 Cu 0.15 Fe 0.15 Co 0.15 Mn 0.15 Ti 0.15 ) 2 O 7-δ The stoichiometric ratios of La, A and B accurately weigh acetates of lanthanum (La), calcium (Ca), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn) and titanium (Ti) respectively.
Example 3:
on the basis of example 1, example 3 adjusts the following parameters.
The Ruddlesden-Popper type high entropy oxide catalyst given in this example has the formula: (La) 0.75 Sr 0.2 Ba 0.05 ) 3 (Ni 0.2 Cu 0.2 Fe 0.2 Cr 0.2 Zn 0.2 ) 2 O 7-δ At this time, a is Sr and Ba, and the molar ratio of Sr to Ba is 4: the molar quantity of the elements of the B is the same as that of the Zn, wherein the B is Ni, cu, fe, cr, the x is 0.25, the n is 2, and the delta is 0.35-1.4.
According to the chemical formula (La) 0.75 Sr 0.2 Ba 0.05 ) 3 (Ni 0.2 Cu 0.2 Fe 0.2 Cr 0.2 Zn 0.2 ) 2 O 7-δ The stoichiometric ratios of La, A and B accurately weigh the nitrate containing lanthanum (La), strontium (Sr), barium (Ba), nickel (Ni), copper (Cu), iron (Fe), chromium (Cr) and zinc (Zn) respectively.
Example 4:
on the basis of example 1, example 4 adjusted the following parameters.
The Ruddlesden-Popper type high entropy oxide catalyst given in this example has the formula: (La) 0.25 Sr 0.75 ) 3 (Ni 0.1 Cu 0.1 Fe 0.1 Co 0.1 Mn 0.1 Ti 0.1 Ga 0.1 Al 0.1 Cr 0.1 Zn 0.1 ) 2 O 7-δ At this time, A is Sr, B is Ni, cu, fe, co, mn, ti, ca, al, cr and Zn, the molar amounts of the elements of B are the same, x is 0.75, n is 2, and delta is 0.35-1.4.
(La 0.25 Sr 0.75 ) 3 (Ni 0.1 Cu 0.1 Fe 0.1 Co 0.1 Mn 0.1 Ti 0.1 Ga 0.1 Al 0.1 Cr 0.1 Zn 0.1 ) 2 O 7-δ The stoichiometric ratio of La, A and B is accurately measured and respectively contains lanthanum (La), strontium (Sr), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), titanium (Ti), gallium (Ga), aluminum (Al), chromium (Cr) and zinc (Zn)Is an acetate salt of (a).
Example 5:
on the basis of example 1, example 5 adjusts the following parameters.
The Ruddlesden-Popper type high entropy oxide catalyst given in this example has the formula: (La) 0.25 Sr 0.75 ) 3 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 ) 2 O 7-δ At this time, A is Sr, B is Ni, cu, fe, co, mn, the molar amounts of the elements of B are the same, x is 0.75, n is 2, and delta is 0.35-1.4.
Press (La) 0.25 Sr 0.75 ) 3 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 ) 2 O 7-δ The stoichiometric ratio of La, A and B accurately weigh the nitrate containing lanthanum (La), strontium (Sr), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co) and manganese (Mn) respectively.
Example 6:
example 6 the following parameters were adjusted on the basis of example 1.
This example shows the chemical formula of a Ruddlesden-Popper type high entropy oxide catalyst: (La) 0.5 Sr 0.25 Ca 0.25 ) 4 (Ni 0.1 Cu 0.1 Fe 0.1 Co 0.1 Mn 0.1 Ti 0.1 Ga 0.1 Al 0.1 Cr 0.1 Zn 0.1 ) 3 O 10-δ At this time, a is Sr and Ca, and the molar ratio of Sr and Ca is 1: the molar quantity of the elements of the B is the same as that of the Zn, wherein the B is Ni, cu, fe, co, mn, ti, ca, al, cr, the value of x is 0.5, the value of n is 3, and the value of delta is 0.5-2.
(La 0.5 Sr 0.25 Ca 0.25 ) 4 (Ni 0.1 Cu 0.1 Fe 0.1 Co 0.1 Mn 0.1 Ti 0.1 Ga 0.1 Al 0.1 Cr 0.1 Zn 0.1 ) 3 O 10-δ In La, A, BThe stoichiometric ratio accurately weighs acetates respectively containing lanthanum (La), strontium (Sr), calcium (Ca), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), titanium (Ti), gallium (Ga), aluminum (Al), chromium (Cr), and zinc (Zn).
Example 7:
example 7 adjusts the following parameters on the basis of example 1.
For the preparation process of example 1, in example 7, after citric acid and ethylenediamine tetraacetic acid are added to the mixed solution until the pH of the mixed solution is 0.5 to 2, the pH of the mixed solution is then adjusted to 8 with ammonia water, and the remaining operation steps and conditions are unchanged.
Example 8:
on the basis of example 1, example 8 adjusts the following parameters.
In example 8, a proper amount of the high-entropy oxide catalyst precursor was poured into a crucible, placed in a tube furnace, calcined in an air atmosphere, heated to 1200 ℃ at a temperature rising rate of 5 ℃/min, kept for 5 hours, cooled to room temperature at a temperature lowering rate of 5 ℃/min, and taken out, as compared with the preparation process of example 1. The rest of the operation steps and conditions are unchanged.
Example 9:
example 9 on the basis of example 1, the following parameters were adjusted.
In example 9, the powder obtained by sufficiently grinding in the above steps was poured into a crucible, placed in a tube furnace, and annealed in a hydrogen-argon mixed atmosphere of 5%H, relative to the production process of example 1 2 And/95% Ar, heating to 500 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, cooling to room temperature at a cooling rate of 5 ℃/min, and taking out. The rest of the operation steps and conditions are unchanged.
Example 10:
on the basis of example 1, example 10 adjusted the following parameters.
In contrast to the preparation process of example 1, the powder obtained in example 10 after sufficiently grinding in the above steps was poured into a crucible, placed in a tube furnace, annealed in a nitrogen atmosphere, raised to 300℃at a temperature-raising rate of 5℃per minute, and kept at the temperature for 0.5 hours, and then cooled to room temperature at a temperature-lowering rate of 5℃per minute, and then taken out. The rest of the operation steps and conditions are unchanged.
Comparative example 1:
on the basis of example 1, comparative example 1 was adjusted for the following parameters.
The Ruddlesden-Popper type high entropy oxide catalyst given in this comparative example has the formula: sr (Sr) 3 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 ) 2 O 7-δ In this case, a is Sr, B is Ni, cu, fe, co and Mn, the molar amounts of the elements of B are the same, x is 1, and n is 2.
According to chemical formula Sr 3 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 ) 2 O 7-δ The stoichiometric ratio of (c) accurately weighs the nitrates of strontium (Sr), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co) and manganese (Mn).
In comparative example 1, which does not contain elemental lanthanum (La), comparative example 1 failed to produce a target sample for performance testing.
Comparative example 2:
on the basis of example 1, comparative example 2 was adjusted for the following parameters.
The Ruddlesden-Popper type high entropy oxide catalyst given in this comparative example has the formula: la (La) 3 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 ) 2 O 7-δ At this time, no element A, B Ni, cu, fe, co and Mn are present, the molar amounts of the elements B are the same, x is 0, n is 2, and δ is less than 0.2.
According to the chemical formula La 3 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 ) 2 O 7-δ Is accurately weighed by the stoichiometric ratio of (2)Nitrate of lanthanum (La), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co) and manganese (Mn).
Comparative example 3:
on the basis of example 1, comparative example 3 was adjusted for the following parameters.
The Ruddlesden-Popper type high entropy oxide catalyst given in this comparative example has the formula: (La) 0.75 Sr 0.25 ) 2 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 )O 4-δ In this case, a is Sr, B is Ni, cu, fe, co and Mn, the molar amounts of the elements of B are the same, x is 0.25, and n is 1.
According to the chemical formula (La) 0.75 Sr 0.25 ) 2 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 )O 4-δ The stoichiometric ratio of lanthanum (La), strontium (Sr), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co) and manganese (Mn) nitrate is accurately weighed.
Comparative example 4:
on the basis of example 1, comparative example 4 was adjusted for the following parameters.
Compared with the preparation process of the embodiment 1, in the comparative example, after citric acid and ethylenediamine tetraacetic acid are added into the mixed solution until the pH value of the mixed solution is 0.5-2, the pH value of the mixed solution is not regulated by ammonia water, the clear solution is heated to form a gel process of a framework structure or a grid structure, the mixed solution with the pH value of 0.5-2 is directly sintered at high temperature, and the rest operation steps and conditions are unchanged.
In comparative example 4, the mixed solution hardly caused high temperature sintering, and the reaction in the mixed solution was also detected to be incomplete, failing to prepare a target sample for performance test.
Comparative example 5:
on the basis of example 1, comparative example 5 was adjusted for the following parameters.
With respect to the preparation process of example 1, this comparative example did not include the subsequent annealing treatment after at least two alternating grinding and high temperature sintering of the solid powder, i.e., the step of "taking an appropriate amount of the powder sufficiently ground in the above step" in example 1, pouring it into a crucible, placing it in a tube furnace, annealing treatment in a nitrogen atmosphere, raising the temperature to 500 ℃ at a rate of 5 ℃/min, and holding the temperature at 1h, and then lowering the temperature to room temperature at a rate of 5 ℃/min, and then taking it out ".
In comparative example 5, the high entropy oxide catalyst prepared was the same as that of example 1, namely (La 0.75 Sr 0.25 ) 3 (Ni 0.2 Cu 0.2 Fe 0.2 Co 0.2 Mn 0.2 ) 2 O 7-δ But delta has a value of less than 0.2.
Comparative example 6:
on the basis of example 1, comparative example 6 was adjusted for the following parameters.
With respect to the preparation process of example 1, this comparative example did not undergo grinding treatment in the subsequent high temperature calcination and annealing steps after high temperature sintering of the gel to obtain dry solid powder.
Comparative example 7:
on the basis of example 1, comparative example 7 was adjusted for the following parameters.
The formula of the Ruddlesden-Popper type mid-entropy oxide catalyst given in this comparative example is: (La) 0.75 Sr 0.25 ) 3 (Ni 0.25 Cu 0.25 Fe 0.25 Co 0.25 ) 2 O 7-δ In this case, A is Sr, B is Ni, cu, fe and Co, the molar amounts of the elements of B are the same, x is 0.25, and n is 2.
According to the chemical formula (La) 0.75 Sr 0.25 ) 3 (Ni 0.25 Cu 0.25 Fe 0.25 Co 0.25 ) 2 O 7-δ The stoichiometric ratio of La, A and B accurately weigh the nitrate containing lanthanum (La), strontium (Sr), nickel (Ni), copper (Cu), iron (Fe) and cobalt (Co) respectively.
Performance test:
the samples obtained in the above examples and comparative examples were used as a performance test for catalytic ammoxidation reactions, and specific test conditions and procedures are as follows:
preparation of 0.5M KOH and 55 mM NH 4 A mixed electrolyte of Cl to simulate an ammonia-containing environment;
under the same conditions, the three-electrode system is adopted for electrochemical test, and the related technological parameters in the electrochemical test method are as follows:
the samples obtained in each example and comparative example are respectively used as catalysts, the catalysts are uniformly mixed with carbon black, nafion, absolute ethyl alcohol and deionized water to obtain slurry, the slurry is coated on clean carbon cloth of 2' 2cm and naturally dried to prepare an electrode slice, the electrode slice is used as a working electrode, ag/AgCl is used as a reference electrode, and a platinum mesh electrode is used as a counter electrode.
In the cyclic voltammogram obtained through the electrochemical test, the adopted scanning speed is 50 mV/s, the scanning potential interval is 0-0.6V, and the number of cycles is 100.
Table 1 table of test results for examples and comparative examples
The data in Table 1, including the results of the tests for the electrocatalytic reaction for ammonia oxidation of the catalysts prepared according to various examples of the present invention, are all higher than 9.5 mA/cm in current density at a relative potential of 0.5V 2 And when the catalyst prepared in example 1 was used in the electrocatalytic reaction for ammoxidation, the current density was the highest at a relative potential of 0.5V and was 12.6 mA/cm 2 。
The test results of the catalyst prepared by each comparative example in the invention for the ammoxidation electrocatalytic reaction are that the current density is lower than 7 mA/cm when the relative potential is 0.5V 2 Wherein the sample of the intermediate entropy oxide obtained in comparative example 7 was used for the ammoxidation electrocatalytic reaction, and the current density was the lowest at a relative potential of 0.5V, and was 3.9 mA/cm 2 . In addition, the target sample could not be prepared in the case of comparative example 1 without La element and in the case of comparative example 4 without pH adjustment of the mixed solution with ammonia water.
As shown in fig. 3, cyclic voltammograms of the catalysts prepared in example 1 and comparative example 7 for the electrocatalytic reaction of ammoxidation are given, and the catalyst obtained in example 1 shows higher current density over the whole scan potential interval when used for the electrocatalytic reaction of ammoxidation.
The test results show that the Ruddlesden-Popper type high-entropy oxide catalyst prepared in each example has remarkable ammoxidation activity.
The high entropy oxide catalyst provided by the invention has excellent ammoxidation activity, which is derived from:
(1) The high entropy oxide catalyst presents micron-sized granularity, so that the active sites are increased, and the catalytic activity is improved;
(2) The Ruddlesden-pop-up high-entropy oxide has highly disordered and distorted crystal lattice, which is favorable for migration of electrons and ions, and the perovskite layer further expands three-dimensional properties, can accommodate high-concentration aliovalent ions, and improves conductivity and catalytic activity;
the combination of elements in A, B in the chemical formula, the high entropy effect and the annealing process introduced in the process of preparing the catalyst lead the obtained high entropy oxide catalyst to have the phenomenon of oxygen defect caused by oxygen overflow, the increase of the content of the oxygen defect further enhances the migration of electrons and ions and improves the catalytic activity;
(3) The synergistic effect between the B elements promotes charge transfer, improves the interface between the electrode and the electrolyte, and thus enhances catalytic activity.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (10)
1. A high entropy oxide catalyst for a fuel cell, comprising:
the chemical formula of the high entropy oxide catalyst is:wherein A is at least one of Ca, sr and Ba, B is at least five of Ni, cu, fe, co, mn, zn, cr, ti, al, ga, the molar ratio of the elements in B is 0.6-1.7, the value of x is 0.075-0.925, and the value of n is 2 or 3;
the crystal structure of the high-entropy oxide catalyst is Ruddlesden-Popper type, delta is oxygen vacancy content, and the value of delta satisfies the following relationship:，/>。
2. the high entropy oxide catalyst for fuel cells according to claim 1, wherein x has a value of 0.25 to 0.75.
3. The high entropy oxide catalyst for fuel cells according to claim 1, wherein B contains Ni and Cu elements.
4. A method for producing the high entropy oxide catalyst for fuel cells according to any one of claims 1 to 3, comprising the steps of:
weighing metal nitrate or acetate containing elements A and B according to stoichiometric ratio, dissolving in deionized water, and magnetically stirring at room temperature to obtain mixed solution;
adding citric acid and ethylenediamine tetraacetic acid into the mixed solution until the pH value of the mixed solution is 0.5-2, and then regulating the pH value of the mixed solution to 6-8 by using ammonia water to obtain a clear solution;
heating the clarified solution to form gel with a skeleton structure or a grid structure, and sintering the gel at high temperature to prepare solid powder;
and (3) carrying out at least two times of alternate grinding and high-temperature calcination on the solid powder, and then carrying out annealing treatment in an inert atmosphere or a reducing atmosphere, wherein the annealing temperature is 100-600 ℃, the annealing time is 0.5-2 h, and the heating and/or cooling rate of annealing is 1-10 ℃/min.
5. The method for producing a high entropy oxide catalyst for fuel cells according to claim 4, wherein the ratio of the total molar amount of the metal elements of A and B to the molar amount of citric acid is 1: 1-1: the ratio of the total molar amount of the metal elements of 4, A and B to the molar amount of ethylenediamine tetraacetic acid is 1: 1-1: 5.
6. the method for preparing a high entropy oxide catalyst for a fuel cell according to claim 4, wherein the clarified solution is heated to form a gel of a skeletal structure or a network structure, specifically:
and heating the clear solution at the heating temperature of 80-160 ℃ for 2-24 hours.
7. The method for preparing a high entropy oxide catalyst for a fuel cell according to claim 6, wherein the clarified solution is heated to form a gel of a skeletal structure or a network structure, specifically:
and heating the clear solution at a heating temperature of 90-110 ℃ for 12-20 hours.
8. The method for preparing a high entropy oxide catalyst for a fuel cell according to claim 4, wherein the gel is sintered at a high temperature, specifically:
and (3) performing high-temperature sintering on the gel at a high-temperature sintering temperature of 320-450 ℃ for 3-6 hours.
9. The method for preparing a high entropy oxide catalyst for a fuel cell according to claim 4, wherein the solid powder is subjected to at least two alternating grinding and high temperature calcination, specifically:
the high-temperature calcination temperature of the solid powder is 500-1200 ℃, the high-temperature calcination time is 2-6 h, and the heating and/or cooling rate of the high-temperature calcination is 1-10 ℃/min.
10. The method for producing a high entropy oxide catalyst for fuel cells according to claim 4, wherein the annealing treatment is performed in an inert atmosphere or a reducing atmosphere, specifically:
the inert atmosphere or the reducing atmosphere is at least one of nitrogen, argon and hydrogen, the annealing temperature is 300-500 ℃, the annealing time is 0.5-1 h, and the heating and/or cooling rate of annealing is 5-10 ℃/min.
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