Ammonia electrode of solid oxide direct ammonia fuel cell and preparation method

Abstract

The invention discloses an ammonia electrode of a solid oxide direct ammonia fuel cell and a preparation method. The ammonia electrode contains Cr or a Cr compound catalyst, the chromium (Cr) or a Cr compound is adopted as an efficient catalyst material, the catalyst is combined with the interior of an electrode structure through technologies such as impregnation and in-situ dissolution, or a stable catalyst layer is formed on the surface of the electrode through methods such as spin coating, spray coating and screen printing. The prepared Cr-based catalyst / layer shows excellent performance and long-term operation stability in an ammonia gas environment, and is suitable for an ammonia electrode of a solid oxide direct ammonia fuel cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell electrode materials, and in particular relates to a high-performance, high-stability solid oxide direct ammonia fuel cell ammonia electrode and a preparation method thereof. Background Art

[0002] Hydrogen is regarded as a preferred fuel for solid oxide fuel cells (SOFCs). However, its low volumetric energy density and high storage and transportation costs have become bottlenecks that hinder the widespread application of hydrogen fuel. In contrast, ammonia, as a carbon-free, high volumetric energy density hydrogen carrier, contains three hydrogen atoms in each molecule, showing many advantages. Ammonia has lower storage and transportation costs, is easy to liquefy, and is safer. These characteristics make ammonia a great development potential as a fuel for SOFCs. In direct ammonia solid oxide fuel cells (DA-SOFCs), the ammonia electrode is the place where ammonia decomposition reactions occur, which requires the ammonia electrode to not only have excellent electrochemical performance and long-term operating stability, but also to have efficient ammonia decomposition catalytic activity.

[0003] At present, the ammonia electrode material commonly used in DA-SOFC is Ni-based cermet. However, the metal-nitrogen binding energy of Ni is relatively low. When ammonia is used as fuel, the ammonia decomposition catalytic activity of the Ni-based ammonia electrode is relatively low, which not only causes the hydrogen partial pressure on the ammonia electrode side to drop, but also causes the undecomposed ammonia to react with Ni to form nickel nitride, further weakening the catalytic activity of the ammonia electrode, thereby affecting the overall performance and stability of the battery. Therefore, it is very important to optimize the ammonia electrode of DA-SOFC, which has a far-reaching impact on improving battery performance and ensuring long-term stable operation.

[0004] Doping Ni-based ammonia electrodes with metals with high catalytic activity can effectively improve the ammonia decomposition rate of the ammonia electrode. Chinese patent CN118538940A discloses a method for preparing a high-performance ammonia catalytic material and a loading scheme for its application in proton ceramic fuel cells. The catalyst composition formula is Ru-CeO2, which is loaded on the ammonia electrode Ni-BaZr of the proton ceramic fuel cell by spraying. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ(BZCYYb). Ru-CeO2 exhibits excellent ammonia catalytic activity. The supported catalytic layer not only helps expand the reaction area on the hydrogen electrode side to enhance the electrochemical performance, but also protects the anode from direct contact with ammonia, inhibits the formation of anodic nitridation reaction at high temperatures, and has better stability. The ammonia decomposition rate of Ru-CeO2 is higher than 99% at 450 °C, and the peak power density reaches 700 mW cm when loaded on the cell at 650 °C. -2 It can operate stably for 150 hours at 600 °C in the cell mode.

[0005] Doping or adding a catalyst (layer) is a simple and convenient way to optimize the ammonia electrode. Currently, the research on non-precious metal catalysts (layers) for Ni-based ammonia electrodes in DA-SOFC mainly focuses on Fe-based catalysts. However, due to the easy sintering property of Fe at high temperatures, its stability is poor. While Cr has higher catalytic activity for ammonia decomposition and metal-nitrogen binding energy than Fe, and it is not prone to coarsening at high temperatures. Summary of the Invention

[0006] In order to solve the problems of insufficient catalytic activity and easy nitridation of traditional ammonia electrode materials in direct ammonia solid oxide fuel cells, the present invention proposes a high-performance and highly stable ammonia electrode for direct ammonia solid oxide fuel cells and a preparation method thereof.

[0007] The technical solution adopted by the present invention is: an ammonia electrode for a direct ammonia solid oxide fuel cell, wherein the ammonia electrode contains a Cr or a compound catalyst of Cr.

[0008] Further, the compound of Cr is an oxide of Cr.

[0009] Further, the oxides of Cr include Cr2O3, CrO3, and CrO.

[0010] A preparation method of an ammonia electrode for a direct ammonia solid oxide fuel cell according to the above, wherein the raw materials of the ammonia electrode for a direct ammonia solid oxide fuel cell are mixed with Cr or a compound catalyst of Cr as a catalyst to prepare the ammonia fuel cell ammonia electrode.

[0011] Further, the raw materials of the ammonia electrode include a barium cerate and barium zirconate solid solution material.

[0012] Further, the barium cerate and barium zirconate solid solution material is BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BCZYYb1711) or BaZr 0.4 Ce 0.4 Y 0.1 Yb 0.1 O3-δ (BCZYYb4411).

[0013] Further, the method specifically includes the following steps:

[0014] Step 1: Mix Cr or a compound of Cr with ammonia electrode raw materials in a predetermined ratio with deionized water, pore former, dispersant, diluted ammonia water, binder, plasticizer, defoamer, and surfactant, and ball mill to obtain ammonia electrode slurry.

[0015] Step 2: After the ammonia electrode slurry is subjected to vacuum degassing treatment, adjust the required knife height on a casting machine for casting to obtain a green body of the ammonia electrode, and perform drying treatment.

[0016] Step 3: After the drying of the green body of the ammonia electrode is completed, perform high-temperature sintering to obtain an ammonia electrode containing a catalyst of Cr or a compound of Cr.

[0017] Step 4: Place the ammonia electrode containing a catalyst of Cr or a compound of Cr in a reducing atmosphere for reduction to obtain an ammonia electrode containing elemental Cr or a low-valence compound.

[0018] A method for preparing an ammonia electrode of an ammonia fuel cell according to the above, impregnate a salt solution of Cr into the pores of the ammonia electrode, or add Cr or a compound of Cr to the surface of the ammonia electrode by spraying, drop coating, spin coating, or coating, and then obtain the ammonia electrode of the ammonia fuel cell through high-temperature calcination and reduction reaction.

[0019] Further, the salt solution of Cr includes CrCl3 solution or Cr(NO3)3·9H2O solution.

[0020] Further, the method specifically includes the following steps:

[0021] Step 1: Mix a salt solution of Cr with deionized water in a predetermined ratio and completely dissolve it to obtain a catalyst solution; or mix Cr2O3 with a binder made of anhydrous ethanol, ethyl cellulose, terpineol, and triethanolamine in a predetermined ratio, mix evenly, and fully grind to obtain a catalytic layer slurry of Cr or a compound of Cr.

[0022] Step 2: Use a pipette or dropper to drop the catalyst solution onto the surface of the internal pores of the battery ammonia electrode; or add the catalytic layer slurry to the surface of the battery ammonia electrode by screen printing, drop coating, spraying, spin coating, or brush coating, and place the battery in an oven for drying.

[0023] Step 3: Place the battery after drying the catalyst or catalytic layer in a muffle furnace for calcination to make the catalyst solution or catalytic layer slurry disperse well and bond stably on the ammonia electrode.

[0024] Step 4: placing the ammonia electrode containing Cr or a Cr compound catalyst in a reducing atmosphere for reduction to obtain an ammonia electrode containing a single substance of Cr or a low-valent compound.

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] (1) The Cr and its compound catalyst (layer) prepared by impregnation, screen printing and other processes is tightly combined with the ammonia electrode, the electrode structure is stable, and the catalyst (layer) particles are uniform in size and have good dispersion.

[0027] (2) Cr and its compounds have excellent catalytic activity for ammonia decomposition and thus can exhibit high electrochemical performance and high stability when applied to the ammonia electrode of direct ammonia solid oxide fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : Wherein a, b are respectively the present invention, BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ Electrochemical impedance diagram of a symmetrical cell Cr|Ni-BZCYYb|BZCYYb|Ni-BZCYYb|Cr and BZCYYb as electrolytes and Ni-BZCYYb as ammonia electrodes prepared with Cr2O3 as ammonia electrode catalyst layer in the range of 700-550℃ under ammonia gas.

[0029] Figure 2 : Wherein a, b, c, d, e and f are the single cell Ni-BZCYYb(support layer)|Ni-BZCYYb(active layer)|LSCF prepared in NH3 atmosphere with LSCF as cathode, BZCYYb as electrolyte, Ni-BZCYYb as ammonia electrode support layer and Ni-BZCYYb as ammonia electrode active layer, and the single cell Cr|Ni-BZCYYb(support layer)|Ni-BZCYYb(active layer)|LSCF prepared in NH3 atmosphere with LSCF as cathode, BZCYYb as electrolyte, Ni-BZCYYb as ammonia electrode support layer, Ni-BZCYYb as ammonia electrode active layer and Cr2O3 as ammonia electrode catalyst layer, respectively obtained by testing in different temperature ranges.

[0030] Figure 3: The figures show the results of fitting the electrochemical impedance spectra (EIS) of the single cells Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF prepared with LSCF as the cathode, BZCYYb as the electrolyte, Ni-BZCYYb as the ammonia electrode support layer, and Ni-BZCYYb as the ammonia electrode active layer, and the single cells Cr|Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF prepared with LSCF as the cathode, BZCYYb as the electrolyte, Ni-BZCYYb as the ammonia electrode support layer, Ni-BZCYYb as the ammonia electrode active layer, and Cr2O3 as the ammonia electrode catalytic layer in an NH3 atmosphere at 650 °C through distribution of relaxation times (DRT).

[0031] Figure 4 : The figures show the stability test results of the single cells Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF prepared with LSCF as the cathode, BZCYYb as the electrolyte, Ni-BZCYYb as the ammonia electrode support layer, and Ni-BZCYYb as the ammonia electrode active layer, and the single cells Cr|Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF prepared with LSCF as the cathode, BZCYYb as the electrolyte, Ni-BZCYYb as the ammonia electrode support layer, Ni-BZCYYb as the ammonia electrode active layer, and Cr2O3 as the ammonia electrode catalytic layer in an NH3 atmosphere at 650 °C.

[0032] Figure 5 : The figure shows the curve of the change in ammonia decomposition rate over time during the discharge stability test of the single cells Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF prepared with LSCF as the cathode, BZCYYb as the electrolyte, Ni-BZCYYb as the ammonia electrode support layer, and Ni-BZCYYb as the ammonia electrode active layer, and the single cells Cr|Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF prepared with LSCF as the cathode, BZCYYb as the electrolyte, Ni-BZCYYb as the ammonia electrode support layer, Ni-BZCYYb as the ammonia electrode active layer, and Cr2O3 as the ammonia electrode catalytic layer in an NH3 atmosphere at 650 °C.

[0033] Figure 6: The present invention relates to the field emission electron microscopy (SEM) and energy dispersive spectrometer (EDS) scanning images of the cross-section after testing of single cells Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF prepared with LSCF as the cathode, BZCYYb as the electrolyte, Ni-BZCYYb as the ammonia electrode support layer, and Ni-BZCYYb as the ammonia electrode active layer under an NH3 atmosphere, and single cells Cr|Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF prepared with LSCF as the cathode, BZCYYb as the electrolyte, Ni-BZCYYb as the ammonia electrode support layer, Ni-BZCYYb as the ammonia electrode active layer, and Cr2O3 as the ammonia electrode catalytic layer. Detailed implementation mode

[0034] The present invention relates to a high-performance and high-stability ammonia electrode for a direct ammonia fuel cell and a preparation method thereof. For the ammonia electrode of the ammonia fuel cell, it contains a catalyst of Cr or a compound of Cr.

[0035] Preferably, the compound of Cr is an oxide of Cr.

[0036] Preferably, the oxides of Cr include Cr2O3, CrO3, and CrO.

[0037] For a preparation method of one of the ammonia electrodes of the ammonia fuel cell, the ammonia electrode raw materials are mixed with Cr or a compound of Cr to prepare the ammonia electrode of the ammonia fuel cell.

[0038] Preferably, the ammonia electrode raw materials include a solid solution material of barium cerate and barium zirconate.

[0039] Preferably, the solid solution material of barium cerate and barium zirconate is BZCYYb, such as BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BCZYYb1711), BaZr 0.4 Ce 0.4 Y 0.1 Yb 0.1 O 3-δ (BCZYYb4411).

[0040] For the above preparation method of the ammonia electrode of the ammonia fuel cell, it specifically includes the following steps:

[0041] Step 1: Mix Cr or a compound of Cr with ammonia electrode raw materials in a predetermined ratio with deionized water, pore-forming agents (such as graphite, carbon black, or starch), dispersants (such as polyacrylic acid), diluted ammonia water, binders (such as polyvinyl alcohol), plasticizers (such as polyethylene glycol), defoamers (such as octane), and surfactants (such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol) and ball-mill to obtain ammonia electrode slurry.

[0042] Step 2: After the ammonia electrode slurry is subjected to vacuum degassing treatment, adjust the required blade height on a casting machine for casting to obtain a green ammonia electrode body, and perform drying treatment.

[0043] Step 3: After the drying of the green ammonia electrode body is completed, perform high-temperature sintering to obtain an ammonia electrode containing a catalyst of Cr or a compound of Cr.

[0044] Step 4: Place the ammonia electrode containing a catalyst of Cr or a compound of Cr in a reducing atmosphere for reduction to obtain an ammonia electrode containing elemental Cr or a low-valence compound.

[0045] Preferably, in Step 1, the mass concentration of Cr or a compound of Cr added to the prepared ammonia electrode slurry is 1-10 wt%. Adding too high a proportion of Cr or a compound of Cr will lead to problems such as uneven dispersion of the ammonia electrode slurry and incomplete dissolution of the solute, affecting the sintering process of the ammonia electrode or resulting in a decrease in the porosity of the electrode.

[0046] Preferably, in Step 3, the calcination temperature is 800-1600 °C, and the heating and cooling rates are 0.2-2 °C / min. -1 Too high a sintering temperature will cause agglomeration of ammonia electrode particles and a decrease in porosity, thereby reducing the ammonia decomposition catalytic activity and the electrochemical performance of the ammonia electrode, while too low a sintering temperature will result in poor bonding between substances and incomplete removal of organic matter in the slurry.

[0047] Preferably, in Step 4, the reducing atmosphere is hydrogen, and the reduction time is 1-10 h. Too short a reduction time will lead to insufficient reduction and low electrochemical performance of the ammonia electrode.

[0048] The following gives another preparation method of an ammonia electrode for an ammonia fuel cell. Immerse a Cr salt solution into the pores of the ammonia electrode, or add Cr or a compound of Cr to the surface of the ammonia electrode by coating, and then obtain the ammonia fuel cell ammonia electrode through calcination and reduction reactions.

[0049] Preferably, the Cr salt solution includes a Cr(NO3)3·9H2O solution or a CrCl3 solution.

[0050] According to the above preparation method of the ammonia fuel cell ammonia electrode, the method specifically includes the following steps:

[0051] Step 1, mix Cr(NO3)3·9H2O or CrCl3 with deionized water in a predetermined ratio and dissolve completely to obtain a catalyst solution; or mix Cr2O3 with a binder made of absolute ethanol, ethyl cellulose, terpineol, and triethanolamine in a predetermined ratio, grind thoroughly, and then calcine and reduce in a high-temperature furnace to obtain a catalytic layer slurry of Cr or a compound of Cr.

[0052] Step 2, use a pipette or dropper to drop the catalyst solution onto the surface of the internal voids of the battery ammonia electrode; or add the catalytic layer slurry to the surface of the battery ammonia electrode by means of screen printing, drop coating, spraying, spin coating, or brush coating, and then place the battery in an oven for drying.

[0053] Step 3, place the battery after drying the catalyst or catalytic layer in a muffle furnace for calcination to ensure that the catalyst solution or catalytic layer slurry is well dispersed and stably bonded in the ammonia electrode.

[0054] Step 4, place the ammonia electrode containing the Cr or compound catalyst of Cr in a reducing atmosphere for reduction to obtain an ammonia electrode containing elemental Cr or a low-valence compound.

[0055] Preferably, in Step 1, the concentration of the solution prepared by Cr(NO3)3·9H2O or CrCl3 and deionized water is 0.1 - 1 mol / L. Too high a concentration of the added Cr(NO3)3·9H2O or CrCl3 solution will cause problems such as uneven dispersion of the ammonia electrode slurry and incomplete dissolution of the solute, affecting the sintering process of the ammonia electrode.

[0056] Preferably, in Step 1, the ratio of Cr2O3 to the binder is 1:1, and the grinding time is 1 - 2 h.

[0057] Preferably, in Step 3, the calcination temperature is 400 - 600 °C, and the heating and cooling rates are 1 °C / min. -1 Too high a sintering temperature will cause agglomeration of ammonia electrode particles and a decrease in porosity, thus reducing the ammonia decomposition catalytic activity and the electrochemical performance of the ammonia electrode. Too low a sintering temperature will result in poor bonding between substances and incomplete removal of organic substances in the slurry.

[0058] Preferably, in Step 4, the reducing atmosphere is hydrogen, and the reduction time is 1 - 10 h. Too short a reduction time will lead to insufficient reduction and low electrochemical performance of the ammonia electrode.

[0059] Example 1:

[0060] This example provides a preparation method for an electrolyte-supported symmetric battery with Cr2O3 as the catalytic layer material, Ni-BZCYYb as the ammonia electrode material, and BZCYYb as the electrolyte material. The specific steps are as follows:

[0061] After thoroughly mixing and grinding BZCYYb powder with a certain proportion of PVB and absolute ethanol, it is pressed into sheets by dry pressing, and then placed in a muffle furnace for calcination. The calcination temperature is 1300 - 1600 °C, and the heating and cooling rates are 1 - 2 °C / min -1 , with a holding time of 4 - 6 h, to obtain BZCYYb electrolyte sheets. Weigh 0.6 g of NiO powder, 0.4 g of BZCYYb powder, 0.1 g of graphite powder, and 1 g of binder made from absolute ethanol, ethyl cellulose, terpineol, and triethanolamine. Mix the powder and the binder evenly and grind thoroughly for 1 - 2 h to obtain a green Ni - BZCYYb ammonia electrode paste. Then, print the Ni - BZCYYb ammonia electrode paste onto the surface of the BZCYYb electrolyte sheet by screen printing, and place it in an 80 °C constant - temperature oven for 20 min to dry. The effective area of screen printing is 0.5 cm 2 , and the screen specification is 150 mesh. Then place it in a muffle furnace for calcination. The calcination temperature is 900 - 1200 °C, and the heating and cooling rates are 1 °C / min -1 , with a holding time of 2 h. After cooling, the prepared symmetric cell without a catalytic layer Ni - BZCYYb|BZCYYb|Ni - BZCYYb is obtained. Weigh 1 g of Cr2O3 powder and 1 g of binder made from absolute ethanol, ethyl cellulose, terpineol, and triethanolamine. Mix the powder and the binder evenly and grind thoroughly for 1 - 2 h to obtain a green Cr2O3 catalytic layer paste. Then, print the Cr2O3 catalytic layer paste onto the surface of the Ni - BZCYYb ammonia electrode by screen printing, and place it in an 80 °C constant - temperature oven for 20 min to dry. The effective area of screen printing is 0.5 cm 2 , and the screen specification is 150 mesh. Then place it in a muffle furnace for calcination. The calcination temperature is 600 - 700 °C, and the heating and cooling rates are 1 °C / min -1 , with a holding time of 2 h. After cooling, the prepared Cr - catalytic - layer symmetric cell Cr|Ni - BZCYYbBZCYYb|Ni - BZCYYb|Cr is obtained.

[0062] In Example 1, the molecular formula of the catalytic - layer material of the symmetric cell is Cr2O3, the molecular formula of the electrode material is NiO - BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb), and the molecular formula of the electrolyte material is BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb)

[0063] Characterization results:

[0064] Fix the prepared symmetric cell on the corundum tube with silver wire, and then place it in the experimental furnace. First, introduce 30 ml / min of -1 hydrogen for reduction, and then introduce ammonia with a flow rate of 20 ml / min -1 to measure the electrochemical impedance spectra of the cell at 700 - 550 °C.

[0065] Figure 1 Figures (a) and (b) in it are the electrochemical impedance spectra of the Cr - catalyzed layer symmetric cell and the non - catalyzed layer symmetric cell at different temperatures under ammonia. The polarization impedance of the Cr - catalyzed layer symmetric cell under ammonia at 700 °C is 0.71 Ω·cm 2 , compared with 3.23 Ω·cm 2 of the non - catalyzed layer symmetric cell, a decrease of 78.02%. This shows that the Cr - catalyzed layer effectively improves the ammonia decomposition catalytic activity and electrochemical performance of the Ni - BZCYYb ammonia electrode.

[0066] Example 2:

[0067] This example provides a preparation method of an ammonia - electrode - supported single cell with Cr2O3 as the catalytic layer material, Ni - BZCYYb as the ammonia - electrode active layer material, Ni - BZCYYb as the ammonia - electrode support layer material, BZCYYb as the electrolyte layer material, and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) as the cathode material, and the specific steps are as follows:

[0068] (1) Add ceramic powder mixture, deionized water, pore - forming agent, dispersant, diluted ammonia water, binder, plasticizer, defoaming agent, and surfactant into the ball - milling tank according to the proportion, and carry out ball - milling to mix evenly to obtain the hydrogen - electrode slurry; add proton - conductor ceramic powder, deionized water, dispersant, diluted ammonia water, binder, plasticizer, defoaming agent, and surfactant into the ball - milling tank according to the proportion, and carry out ball - milling to mix evenly to obtain the electrolyte slurry;

[0069] (2) Mix the hydrogen - electrode slurry and the electrolyte slurry separately until uniform. After vacuum degassing treatment, adjust the required blade height on the tape - casting machine for composite tape - casting to obtain an electrolyte / hydrogen - electrode composite membrane green body, and dry it;

[0070] (3) After the electrolyte / hydrogen - electrode composite membrane green body is dried, take it down, cut it into green body slices of the required size, place them isostatically, and after drying and debinding, co - fire the green body slices to obtain a Ni - BZCYYb (support layer)|Ni - BZCYYb (active layer)|BZCYYb half - cell.

[0071] (4) The LSCF slurry was printed onto the surface of the half-cell electrolyte as the battery cathode by screen printing, and then placed in an oven at 80 °C for 20 min to dry. The effective area of screen printing was 0.5 cm 2 , and the screen specification was 150 mesh. Then it was placed in a muffle furnace for calcination. The calcination temperature was 1000 - 1100 °C, and the heating and cooling rates were 1 °C / min -1 , and the holding time was 2 h.

[0072] (5) The Cr2O3 catalytic layer slurry was printed onto the surface of the battery ammonia electrode by screen printing, and then placed in an oven at 80 °C for 20 min to dry. The effective area of screen printing was 0.5 cm 2 , and the screen specification was 150 mesh. Then it was placed in a muffle furnace for calcination. The calcination temperature was 600 - 700 °C, and the heating and cooling rates were 1 °C / min -1 , and the holding time was 2 h. After cooling, the prepared single cell Cr|Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF was taken out.

[0073] In Example 2, the molecular formula of the battery cathode material composition was La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF), the molecular formula of the electrolyte material composition was BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb), the molecular formula of the ammonia electrode active layer material composition was Ni-BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb), the molecular formula of the ammonia electrode support layer material composition was, and the molecular formula of the ammonia electrode catalytic layer material composition was Cr2O3. By attaching a catalytic layer to the surface of the ammonia electrode of the direct ammonia solid oxide fuel cell, the electrochemical performance and long-term operation stability of the battery were significantly improved. At 700 °C, the maximum power density of the single cell Cr|Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF was 1030 mW / cm -2 ; the maximum output power of the corresponding single cell Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF without a catalytic layer was only 463 mW / cm -2 , an increase of 122.46%.

[0074] Characterization results:

[0075] 1. Single cell performance test

[0076] Seal the prepared single cell onto the corundum tube with ceramic glue, then place it in the experimental furnace. Pass air with a flow rate of 80 ml / min into the cathode side of the cell, and pass ammonia with a flow rate of 20 ml / min -1 into the ammonia electrode side, and test the electrochemical performance of the cell at 700 - 395 °C respectively. -1 Figure 2 Figures for the I-V-P curves of the single cells Cr|Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF and Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF at different temperatures are shown as follows. As shown in the figure, at 700 °C, the open circuit voltages of both cells are greater than 1 V, indicating that the electrolyte is dense and the cell is well sealed.

[0077] As Figure 2 shown, the maximum power densities of the single cell Cr|Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF at 700, 650, 600, 550, 500, 450, 400, 3395 °C are 1030.21, 782.2, 578.37, 399.39, 259.92, 174.17, 146.52, 130.32 mW / cm -2 ² respectively, and the polarization resistances are 0.07, 0.15, 0.30, 0.68, 1.72, 3.74, 5.26, 6.26 Ω·cm 2 ²; while the maximum power densities of the single cell Ni-BZCYYb (support layer)|Ni-BZCYYb (active layer)|LSCF at 700, 650, 600, 550 °C are 463.67, 323.07, 202.11, 117.94 mW / cm -2 ² respectively, and the polarization resistances are 0.19, 0.32, 0.68,

[0078] 1.42 Ω·cm 2 ². It can be seen that when ammonia is used as fuel, the addition of the Cr catalytic layer can effectively improve the maximum power density of the single cell and reduce the polarization resistance of the single cell.

[0079] Figure 3 ​It is a comparative diagram of the results of the distribution of relaxation time (DRT) method of the impedance of a single cell with a Cr catalytic layer and a single cell without a catalytic layer at 650 °C. Among them, the P1 and P2 peaks in the high-frequency band correspond to the processes of proton and charge transport and hydrogen adsorption and dissociation respectively. The P3 and P4 peaks in the middle-frequency band correspond to the transport of oxygen ions and the reactions at the three-phase interface respectively. And the P5 peak in the low-frequency band corresponds to the gas diffusion process. Compared with the cell without a catalytic layer, in the DRT results of the cell with a Cr catalytic layer, the heights and peak areas of the polarization peaks P1, P2, and P5 decrease, and the peak positions shift to the high frequency, indicating that the addition of the Cr catalytic layer can increase the ammonia decomposition rate, thus promoting the proton transport and hydrogen adsorption and dissociation processes of the cell, and being beneficial to the gas diffusion and transport processes at the electrode.

[0080] 2. Characterization of the stability of the single cell

[0081] The long-term stability of the cell is also an important criterion for measuring the performance of the cell. Therefore, long-term stability tests were carried out on the cells with a Cr catalytic layer and without a catalytic layer. As Figure 4 shown, at 650 °C, the cell without a catalytic layer was tested with an externally applied current density of 0.32 A cm -2 , and the cell with a Cr catalytic layer was tested with an externally applied current density of 0.45 A cm -2 . After 300 h of discharge, the voltage of the cell with a Cr catalytic layer remained stable. The stable time of the cell without a catalytic layer was less than that of the cell with a Cr catalytic layer, and the voltage fluctuated after 372 h of constant current discharge. Therefore, the addition of the Cr catalytic layer can also improve the long-term stability of the cell.

[0082] Figure 5 Figures a and b are the field emission electron microscope (SEM) and energy dispersive spectrometer (EDS) scanning images of the cross-section of the cell without a catalytic layer and the cell with a Cr catalytic layer after the stability test. It can be seen from the figures that the Cr catalytic layer is well combined with the Ni-BZCYYb electrode layer, and the cell still has a certain porosity after the test.

[0083] 3. Characterization of the microscopic morphology of the cell after the test

[0084] Figure 6 Figures a and b are the field emission electron microscope (SEM) and energy dispersive spectrometer (EDS) scanning images of the cross-section of the cell without a catalytic layer and the cell with a Cr catalytic layer after the test. It can be seen from the figures that the Cr catalytic layer is well combined with the Ni-BZCYYb electrode layer, and the cell still has a certain porosity after the test.

[0085] The present invention discloses a catalyst (layer) material for a direct ammonia fuel cell with high performance and high stability and a preparation method thereof, and a Cr-based catalyst (layer) can be obtained for an ammonia electrode of a direct ammonia solid oxide fuel cell, which has a large specific surface area, is uniformly distributed, and has relatively light particle agglomeration.

[0086] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A solid oxide direct ammonia fuel cell ammonia electrode, characterized in that: The ammonia electrode contains Cr or a Cr compound catalyst.

2. The solid oxide direct ammonia fuel cell ammonia electrode according to claim 1, characterized in that: The Cr compound is Cr oxide.

3. The solid oxide direct ammonia fuel cell ammonia electrode according to claim 2, characterized in that: The Cr oxides include Cr2O3, CrO3, and CrO.

4. The method for preparing ammonia electrode of solid oxide direct ammonia fuel cell according to any one of claims 1 to 3, characterized in that: The ammonia electrode of ammonia fuel cell is prepared by mixing ammonia electrode raw materials of a solid oxide direct ammonia fuel cell with Cr or a Cr compound as a catalyst.

5. The method for preparing ammonia electrode of solid oxide direct ammonia fuel cell according to claim 4, characterized in that: The ammonia electrode raw material includes barium ceria and barium zirconate solid solution materials.

6. The method for preparing ammonia electrode of solid oxide direct ammonia fuel cell according to claim 5, characterized in that: The solid solution material of barium ceria and barium zirconate is BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BCZYYb1711) or BaZr 0.4 Ce 0.4 Y 0.1 Yb 0.1 O 3-δ (BCZYYb4411).

7. The method for preparing ammonia electrode of solid oxide direct ammonia fuel cell according to claim 4, characterized in that: The method specifically comprises the following steps: Step 1, mixing Cr or a Cr compound and an ammonia electrode raw material with deionized water, a pore-forming agent, a dispersant, diluted ammonia water, a binder, a plasticizer, a defoamer, and a surfactant in a predetermined ratio and ball-milling to obtain an ammonia electrode slurry; Step 2, after the ammonia electrode slurry is subjected to vacuum degassing treatment, the required blade height is adjusted on a casting machine for casting to obtain an ammonia electrode blank, and then drying is performed; Step 3, after the ammonia electrode green sheet is dried, high-temperature sintering is performed to obtain an ammonia electrode containing Cr or a Cr compound catalyst; Step 4: placing the ammonia electrode containing Cr or a Cr compound catalyst in a reducing atmosphere for reduction to obtain an ammonia electrode containing a single substance of Cr or a low-valent compound.

8. The method for preparing a solid oxide direct ammonia fuel cell ammonia electrode according to any one of claims 1 to 3, characterized in that: The Cr salt solution is impregnated into the gaps of the ammonia electrode, or Cr or a Cr compound is added to the surface of the ammonia electrode by spraying, dripping, spin coating or coating, and then the ammonia electrode of the ammonia fuel cell is obtained through high-temperature calcination and reduction reaction.

9. The method for preparing ammonia electrode of solid oxide direct ammonia fuel cell according to claim 8, characterized in that: The salt solution of Cr includes CrCl3 solution or Cr(NO3)3·9H2O solution.

10. The method for preparing ammonia electrode for solid oxide direct ammonia fuel cell according to claim 8, characterized in that: The method specifically comprises the following steps: Step 1, mixing a Cr salt solution with deionized water in a predetermined ratio and completely dissolving them to obtain a catalyst solution; or mixing Cr2O3 with a binder made of anhydrous ethanol, ethyl cellulose, pinene alcohol, and triethanolamine in a predetermined ratio, and fully grinding them to obtain a catalyst layer slurry of Cr or a Cr compound; Step 2, using a pipette or dropper, drip the catalyst solution onto the surface of the internal gap of the battery ammonia electrode; or using screen printing, drip coating, spray coating, spin coating or brush coating to add the catalyst layer slurry to the surface of the battery ammonia electrode, and placing the battery in an oven for drying; Step 3, placing the catalyst or the catalyst layer after drying into a muffle furnace for calcination, so that the catalyst solution or the catalyst layer slurry is well dispersed in the ammonia electrode and stably combined; Step 4: placing the ammonia electrode containing Cr or a Cr compound catalyst in a reducing atmosphere for reduction to obtain an ammonia electrode containing a single substance of Cr or a low-valent compound.

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