Preparation of high-activity in-situ precipitated iron-nickel alloy anode catalyst and its application in direct ammonia solid oxide fuel cell

Abstract

The application belongs to the technical field of solid oxide fuel cell anode catalyst, and particularly relates to preparation of a high-activity in-situ precipitated iron-nickel alloy anode catalyst and application thereof in a direct ammonia solid oxide fuel cell. 2‑x Ni x O4, which is in-situ precipitated Fe 2‑x Ni x under a reducing atmosphere, is anchored on the surface of a ZnO catalyst with rich oxygen vacancy concentration in the form of an alloy to form an Fe 2‑x Ni x / ZnO (0 < x < 0.1) anode catalyst. The obtained Fe 2‑x Ni x / ZnO anode phase is made into a slurry and then assembled into a solid oxide fuel cell single cell sheet. The solid oxide fuel cell prepared by the application has good power output, electrical conductivity and stability at medium-high temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid oxide fuel cell anode catalysts, and particularly relates to a method for preparing an anode catalyst using a spinel oxide as a precursor and its application in solid oxide fuel cells. Background Art

[0002] A fuel cell is an energy conversion device that directly and continuously converts the chemical energy of reactants, such as fuel, into electricity through an electrochemical pathway, efficiently and environmentally friendly. During the electrochemical reaction, electrons and ions migrate through the electrolyte and the external current, respectively, generating current that outputs energy. As an energy conversion device, fuel cells do not rely on fuel combustion. Unlike traditional energy conversion processes such as heat engines, fuel cells are limited by the ideal efficiency of the Carnot cycle, but their actual energy efficiency can reach 50–80%. Fuel cells generally consist of three components: a cathode, an anode, and an electrolyte. The output performance of a fuel cell is closely related to the properties of the anode material. Currently, research in anode materials focuses on the development of new materials and diverse structural compositions. On the anode side, the reaction is primarily concentrated in the hydrogen oxidation reaction (HOR). Current research on enhancing activity focuses on perovskite materials. However, perovskite materials contain alkaline earth metals (Ca, Sr, and Ba), which react chemically with the electrolyte material (YSZ), reducing the three-phase interface, increasing the cell's resistance, and thus reducing its output performance.

[0003] Spinel belongs to the cubic crystal system, so its thermal expansion and thermal conductivity are the same in all directions, and the coefficient is small, resulting in excellent thermal stability of spinel. It is precisely because of these advantages of spinel materials that it has attracted widespread attention from researchers, making it shine in the field of new batteries, especially solid oxide fuel cells. At present, magnesium, manganese, iron, nickel, copper, and cobalt spinels have all been studied (Nanoscale, 2015, 7 (19): 8920-8930; Chemical Communications, 2016, 52, 8615-8618; Powder Technology, 2012, 217: 330-339.). The thermal expansion coefficient of cobalt-based spinel is poorly matched with solid electrolyte materials and is not suitable for long-term use (Solid State Ionics, 2015, 276: p.62-71.). For traditional NiO anode materials, there are often problems with complex processes and poor stability (CN 113991135 A). Some selectively doped single perovskite anode materials contain alkaline earth metal elements such as Sr, which easily react with the electrolyte YSZ to form a non-conductive phase, which limits their performance output and long-term operation (ZL 200810056546.3, CN 101964422A). Summary of the Invention

[0004] The present invention mainly addresses the deficiencies of current materials and proposes the preparation of a highly active in-situ precipitated iron-nickel alloy anode catalyst and its application in direct ammonia solid oxide fuel cells. The anode catalyst in the present invention has good chemical and thermal compatibility with commonly used solid electrolytes and has good output performance at the operating temperature of the fuel cell, providing a material option for solid oxide fuel cell anode catalysts.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A high-activity in-situ precipitation iron-nickel alloy anode catalyst, the anode catalyst composition is Fe 2-x Ni x / ZnO, wherein 0≤x≤0.1, preferably 0<x<0.1, and more preferably x = 0.05.

[0007] A method for preparing a high-activity in-situ precipitation iron-nickel alloy anode catalyst, in which spinel ZnFe 2-x Ni x O4 oxide in situ precipitation alloy Fe 2-x Ni x , where 0≤x≤0.1, and anchored on the surface of ZnO catalyst with rich oxygen vacancy concentration, a spinel anode catalyst Fe 2-x Nix / ZnO.

[0008] The spinel ZnFe 2-x Ni x O4 oxide and Fe 2-x Ni x The method for preparing ZnO anode phase powder comprises the following steps:

[0009] 1) According to the stoichiometric ratio, weigh 2.20 g (CH3COO)2Zn•2H2O, 7.68-8.08 g Fe(NO3)3•9H2O, and 0-0.29 g Ni(NO3)2•6H2O, respectively. Dissolve the above crystals in 100-200 mL of deionized water to obtain the corresponding metal salt aqueous solution. Stir thoroughly with a magnetic stirrer for 60-120 min to obtain a mixed solution A.

[0010] 2) adding a complexing agent to the solution A obtained in step 1) to obtain a mixed solution B;

[0011] 3) Adjust the pH of solution B with a buffer solution, then perform a water bath reaction until the water in solution B evaporates completely to obtain a wet gel;

[0012] 4) The obtained wet gel was placed in an oven and dried at 120-180 °C for 12-24 h, then ground into powder and calcined by programmed temperature to obtain spinel ZnFe 2-x Ni x O4 oxide.

[0013] 5) After the spinel oxide is reduced by programmed temperature in a reducing atmosphere, the anode phase Fe 2-x Ni x / ZnO.

[0014] The complexing agent in step 2) is a mixed solution of citric acid, EDTA and ethylene glycol, and the ratio of the amount of total metal ion substance, citric acid, EDTA and ethylene glycol in the mixed solution B is (1.0-1.5): (1.0-2.0): (1.0-2.0): (1-2.0).

[0015] The buffer solution in step 3) is one of ammonia-ammonium chloride buffer solution, triethylamine buffer solution, and ethylenediamine buffer solution; the pH value after adjustment in step 3) is in the range of 6-10.

[0016] Step 3) The water bath reaction is specifically carried out by placing the mixture in a water bath at 60-90° C. and stirring the mixture for 4-8 hours.

[0017] The programmed calcination temperature in step 4) is 900-1100°C, and the calcination time is 1-8 h.

[0018] The reducing atmosphere in step 5) is a H2 / Ar mixed gas with a volume fraction of 10%, the programmed temperature reduction temperature is 600-800°C, and the calcination time is 6-12 h.

[0019] Application of a high-activity in-situ precipitated iron-nickel alloy anode catalyst in a direct ammonia solid oxide fuel cell comprises the following steps:

[0020] (1) Add terpineol solution containing ethyl cellulose to the anode catalyst Fe 2-x Ni x / ZnO, and after thorough mixing, obtain anode slurry;

[0021] (2) The obtained anode slurry is brushed onto the anode side of an electrolyte-supported half-cell sheet with a cathode of LaSrMnO3 (LSM)-YSZ and an electrolyte of YSZ by screen printing to obtain a fuel cell sheet. The single cell is then placed in a muffle furnace and sintered at 900-1100 °C for 1-8 h, cooled to room temperature, and the heating and cooling rates are 0.5-10 °C / min to obtain a solid oxide fuel cell single cell sheet.

[0022] In step (1), the binder is a mixture of ethyl cellulose and terpineol, wherein the content of ethyl cellulose is between 1-4wt%.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. This invention provides the preparation of a highly active in-situ precipitated iron-nickel alloy anode catalyst and its application in direct ammonia solid oxide fuel cells. By doping nickel at the B site and then in-situ precipitating the iron-nickel alloy in a hydrogen-reducing atmosphere and anchoring it on the ZnO surface, the catalyst enhances electronic conductivity and increases reactive sites, significantly improving single-cell output performance.

[0025] 2. Unreduced ZnO acts as an oxide support, which improves the dispersion of alloy particles and contains a certain concentration of oxygen vacancies, providing a new pathway for oxygen ion conduction.

[0026] 3. Fe 2-x Ni x The ZnO anode phase does not contain alkaline earth elements and will not react with the solid electrolyte and carbon dioxide in the air under high temperature conditions, thereby improving the long-term stability of the battery.

[0027] 4. When the Ni doping amount is appropriate, the utilization rate of ammonia can be effectively improved, which also indicates the possibility of ammonia replacing hydrogen as one of the clean energy carriers. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 XRD spectra of ZnFe2O4 in Example 1 of the present invention after calcination at 1100°C for 2 hours (a) and reduction at 800°C under 10% H2 / Ar for 6 hours (b).

[0029] Figure 2 Fe 2-x Ni x / ZnO|YSZ|LSM-60YSZ battery at 600-800 ℃ and 50 mL / min NH3 IVP Figure (a) and impedance spectrum (b); DETAILED DESCRIPTION

[0030] In order to make the contents of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0031] Example 1

[0032] Preparation of Fe / ZnO anode slurry and its single cell:

[0033] (1) According to the stoichiometric ratio, 2.20 g (CH3COO)2Zn•2H2O and 8.08 g Fe(NO3)3•9H2O were weighed and dissolved in 200 mL of deionized water to obtain the corresponding nitrate aqueous solution. The solution was stirred with a magnetic stirrer for 60 min to obtain a mixed solution A.

[0034] (2) adding a mixed solution of citric acid, EDTA and ethylene glycol to the solution A obtained in (1) to obtain a mixed solution B, wherein the ratio of the amount of the total metal ion substance added, the amount of citric acid, EDTA and ethylene glycol is 1.0:2.0:1.0:1.0;

[0035] (3) Use ammonia-ammonium chloride buffer solution to adjust the pH value of solution B to 9, then place it in an 80°C water bath and stir for 6 h to obtain a wet gel after the water in solution B evaporates completely;

[0036] (4) The obtained wet gel was placed in an oven, dried at 120 °C for 12 h, ground into powder, and heated to 400 °C at a heating rate of 2 °C / min and kept at this temperature for 4 h to obtain pretreated powder; then the temperature was further heated to 1100 °C at a heating rate of 2 °C / min and calcined for 2 h to obtain spinel oxide ZnFe2O4;

[0037] (5) The obtained spinel oxide ZnFe2O4 was heated to 800°C at a heating rate of 2°C / min and reduced in a 10% by volume H2 / Ar mixed gas for 6 h to obtain the anodic phase Fe / ZnO.

[0038] (6) adding a terpineol solution containing 4 wt% ethyl cellulose and terpineol to the anode powder obtained in (5), and mixing them evenly to obtain an anode slurry;

[0039] (7) The anode slurry was applied by screen printing on the anode side of the electrolyte-supported half-cell sheet with LaSrMnO3 (LSM)-YSZ as cathode and YSZ as electrolyte to obtain a fuel cell sheet. The single cell was then placed in a muffle furnace and sintered at 1100 °C for 2 h, cooled to room temperature, and the heating and cooling rate was 10 °C / min to obtain a solid oxide fuel cell single cell sheet.

[0040] Example 2

[0041] The specific preparation method of this embodiment is basically the same as that of Example 1, except that 0.058 g Ni(NO3)2•6H2O is added to the raw materials in step (1), and the corresponding anode phase obtained is Fe 1.98 Ni 0.02 / ZnO (i.e. n Fe :n Ni = 1.98:0.02, that is, x = 0.02).

[0042] Example 3

[0043] The specific preparation method of this embodiment is basically the same as that of Example 1, except that 0.15 g Ni(NO3)2•6H2O is added to the raw materials in step (1), and the corresponding anode phase obtained is Fe 1.95 Ni 0.05 / ZnO (i.e. n Fe :n Ni = 1.95:0.05, that is, x = 0.05).

[0044] Example 4

[0045] The specific preparation method of this embodiment is basically the same as that of Example 1, except that 0.23 g Ni(NO3)2•6H2O is added to the raw materials in step (1), and the corresponding anode phase obtained is Fe 1.92 Ni 0.08 / ZnO (i.e. n Fe :n Ni = 1.92:0.08, that is, x =0.08).

[0046] Example 5

[0047] The specific preparation method of this embodiment is basically the same as that of Example 1, except that 0.29 g Ni(NO3)2•6H2O is added to the raw materials in step (1), and the corresponding anode phase obtained is Fe 1.9 Ni 0.10 / ZnO (i.e. n Fe :n Ni = 1.9:0.10, that is, x =0.10).

[0048] Example 6

[0049] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the mass ratio of the binder ethyl cellulose and terpineol in step (6) is 2:1.

[0050] Example 7

[0051] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the mass ratio of the binder ethyl cellulose and terpineol in step (6) is 3:1.

[0052] Example 8

[0053] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the ratio of the amount of the total metal ion substance, citric acid, EDTA and ethylene glycol added in step (2) is 1.0:1.5:2:1.0.

[0054] Example 9

[0055] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the ratio of the amount of the total metal ion substance, citric acid, EDTA and ethylene glycol added in step (2) is 1:2:5:2.0.

[0056] Example 10

[0057] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the ammonia buffer solution in step (3) is changed to a triethylamine buffer solution, and the pH value is changed to 6.

[0058] Example 11

[0059] The specific preparation method of this embodiment is basically the same as that of Example 1, except that in step (3), the ammonia-ammonium chloride buffer solution is changed to an ethylenediamine buffer solution, and the pH value is changed to 8.

[0060] Example 12

[0061] The specific preparation method of this embodiment is basically the same as that of Example 1, except that in step (3), the ammonia-ammonium chloride buffer solution is changed to an ethylenediamine buffer solution, and the pH value is changed to 10.

[0062] Example 13

[0063] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the water bath temperature in step (3) is changed from 80°C to 60°C.

[0064] Example 14

[0065] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the water bath temperature in step (3) is changed from 80°C to 90°C.

[0066] Example 15

[0067] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the water bath time in step (3) is changed from 6 h to 8 h.

[0068] Example 16

[0069] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the water bath time in step (3) is changed from 6 h to 4 h.

[0070] Example 17

[0071] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the drying temperature in step (4) is changed from 120°C to 150°C.

[0072] Example 18

[0073] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the drying temperature in step (4) is changed from 120°C to 180°C.

[0074] Example 19

[0075] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the drying time in step (4) is changed from 12 h to 24 h.

[0076] Example 20

[0077] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the drying time in step (4) is changed from 12 h to 18 h.

[0078] Example 21

[0079] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the calcination temperature in step (4) is changed from 1100°C to 1000°C.

[0080] Example 22

[0081] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the calcination temperature in step (4) is changed from 1100°C to 900°C.

[0082] Example 23

[0083] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the calcination time in step (4) is changed from 2 h to 4 h.

[0084] Example 24

[0085] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the calcination time in step (4) is changed from 2 h to 3 h.

[0086] Example 25

[0087] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the reduction temperature in step (5) is changed from 800°C to 700°C.

[0088] Example 26

[0089] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the reduction temperature in step (5) is changed from 800°C to 600°C.

[0090] Example 27

[0091] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the reduction time in step (5) is changed from 6 h to 8 h.

[0092] Example 28

[0093] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the reduction time in step (5) is changed from 6 h to 10 h.

[0094] Example 29

[0095] The specific preparation method of this embodiment is basically the same as that of Example 1, except that the reduction time in step (5) is changed from 6 h to 12 h.

[0096] Product performance test:

[0097] The single cell is made of electrolyte-supported YSZ (Ningbo Suofuman Energy Technology Co., Ltd., diameter 15 mm). The cathode layer is LaSrMnO3 (LSM)-60YSZ (the mass ratio of LSM powder to YSZ is 2:3) with a diameter of 5 mm. The anode layer is Fe 2- x Ni x / ZnO, with a diameter of 10 mm. The electrodes were coated using screen printing. The cathode slurry was printed on the air side of the YSZ electrolyte support sheet and dried at 80°C for 30 minutes. The anode slurry was then applied to the fuel gas side using the same method.

[0098] The single cell assembly process is as follows: First, apply silver paste (5 × 5 mm square) to the cathode side as a current collector. Second, place a platinum wire and nickel mesh on the nozzle of the reactor, with the anode side of the single cell facing the fuel gas. Third, place a silver mesh (same size as the silver paste) on the cathode side, and then place the platinum wire on top, ensuring a tight connection. Finally, seal the joints of the reactor with ceramic adhesive to ensure a tight seal. Apply platinum paste between the platinum wire and the current collector to ensure a tight connection. The fuel cell performance was measured using the two-electrode method, with silver wires connecting the positive and negative electrodes of an electrochemical workstation (Zahner IM6). Under laboratory conditions, 50 mL / min of NH3 was passed through the IM6 electrochemical analyzer. The output power density, current density, and polarization impedance of the resulting fuel cell were measured at 800°C. The results are shown in Table 1.

[0099] Table 1 Output power density, current density, and polarization impedance of direct ammonia solid oxide fuel cell at 800 ℃

[0100]

[0101] It can be seen from Table 1 that when the calcination temperature is 1100 ℃ for 2 h and the reduction temperature is 800 ℃ for 6 h, the Fe 2-x Ni x The best performance was achieved when Mg / ZnO was used as the anode phase. Furthermore, different nickel doping levels, different buffers, and adjusted pH values ​​all affected the performance of the single cell. The best performance was achieved when x = 0.05 and the pH was adjusted to 9 using an ammonia-ammonium chloride buffer solution.

[0102] from Figure 1 As can be seen in Figure a, obvious characteristic peaks are shown at the (111), (220), (311), (400), (422), (511) and (440) crystal planes, corresponding to JCPDS standard card NO.01-082-1042, indicating that ZnFe2O4 has a cubic spinel structure and a space group of Fd m. Figure 1 The results in b show that ZnFe2O4 forms Fe / ZnO phase after reduction.

[0103] from Figure 2 Single battery in a IVP The results show that the peak power density of the series of samples is higher than that of the traditional anode catalyst NiO, and when the Ni doping amount is 0.05, that is, the anode catalyst component is Fe 1.95 Ni 0.05 / ZnO, the peak power density of the single cell is the highest. Figure 2 The impedance spectrum of the single cell in Figure b shows that the anode catalyst is Fe 1.95 Ni 0.05 / ZnO has the smallest polarization impedance, which corresponds to the single cell output performance.

[0104] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a high-activity in-situ precipitation iron-nickel alloy anode catalyst, characterized by: In reducing atmosphere, spinel ZnFe 2-x Ni x O4 oxide in situ precipitation alloy Fe 2-x Ni x , where 0<x≤0.1, and anchored on the surface of ZnO catalyst with rich oxygen vacancy concentration, a spinel anode catalyst Fe 2-x Ni x / ZnO; Fe 2-x Ni x The preparation method of ZnO anode catalyst comprises the following steps: 1) According to the stoichiometric ratio, weigh 2.20 g (CH3COO)2Zn•2H2O, 7.68-8.08 g Fe(NO3)3•9H2O, and 0-0.29 g Ni(NO3)2•6H2O, respectively, and fully dissolve them in 100-200 mL deionized water to obtain the corresponding metal salt aqueous solution. Stir thoroughly with a magnetic stirrer for 60-120 min to obtain a mixed solution A. 2) adding a complexing agent to the solution A obtained in step 1) to obtain a mixed solution B; 3) Adjust the pH of solution B with a buffer solution, then perform a water bath reaction until the water in solution B evaporates completely to obtain a wet gel; 4) The obtained wet gel was placed in an oven and dried at 120-180 °C for 12-24 h, then ground into powder and calcined by programmed temperature to obtain spinel ZnFe 2-x Ni x O4 oxide; 5) After the spinel oxide is reduced by programmed temperature in a reducing atmosphere, the anode phase Fe 2-x Ni x / ZnO.

2. The preparation method according to claim 1, wherein: The complexing agent in step 2) is a mixed solution of citric acid, EDTA and ethylene glycol, and the ratio of the amount of total metal ion substance, citric acid, EDTA and ethylene glycol in the mixed solution B is (1.0-1.5): (1.0-2.0): (1.0-2.0): (1.0-2.0).

3. The preparation method according to claim 1, wherein: The buffer solution in step 3) is one of ammonia-ammonium chloride buffer solution, triethylamine buffer solution, and ethylenediamine buffer solution; and the pH value in step 3) is adjusted to a range of 6-10.

4. The preparation method according to claim 1, wherein: Step 3) The water bath reaction is specifically carried out by placing the mixture in a water bath at 60-90° C. and stirring the mixture for 4-8 hours.

5. The preparation method according to claim 1, wherein: The programmed calcination temperature in step 4) is 900-1100°C, and the calcination time is 1-8 h.

6. The preparation method according to claim 1, wherein: The reducing atmosphere in step 5) is a H2 / Ar mixed gas with a volume fraction of 10%, the programmed temperature reduction temperature is 600-800°C, and the calcination time is 6-12 h.

7. The iron-nickel alloy anode catalyst Fe prepared by the preparation method according to any one of claims 1 to 6 2-x Ni x / ZnO.

8. Use of the iron-nickel alloy anode catalyst in a direct ammonia solid oxide fuel cell according to claim 7, characterized in that: The following steps are involved: (1) Add the mixture of ethyl cellulose and terpineol to the iron-nickel alloy anode catalyst Fe 2-x Ni x / ZnO, and after thorough mixing, obtain anode slurry; (2) The obtained anode slurry is brushed onto the anode side of the electrolyte-supported half-cell sheet with LSM-YSZ as the cathode and YSZ as the electrolyte by screen printing to obtain a fuel cell sheet. The single cell is then placed in a muffle furnace and sintered at 900-1100 °C for 1-8 h with a heating and cooling rate of 0.5-10 °C / min to obtain a direct ammonia solid oxide fuel cell single cell sheet.

9. The use according to claim 8, characterized in that: In the mixed solution of ethyl cellulose and terpineol in step (1), the content of ethyl cellulose is between 1-4 wt%.

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