IrSA-Ni3N-t twin-crystal nanosheet electrocatalyst as well as preparation method and application thereof

Abstract

The invention discloses an IrSA-Ni3N-t twin crystal nanosheet electrocatalyst as well as a preparation method and application thereof, and belongs to the technical field of two-dimensional nano material catalysts. According to the preparation method, the Ir-atom-doped Ni3N twin crystal nanosheet is prepared by simply nitriding the Ir-substituted nickel hydroxide nanosheet through a high-temperature annealing method. According to the prepared IrSA-Ni3N-t twin crystal nanosheet electrocatalyst, Ir monatomic is doped in Ni3N crystal lattices to reduce stacking fault energy, twin crystals are induced to be formed through high-temperature nitridation, the capacity of a reaction interface for hydroxyl adsorption and transmission and hydrogen bond network connectivity is effectively adjusted, and therefore the alkaline hydroxide reaction performance is improved. The catalyst shows catalytic activity, CO tolerance and long-term stability which are obviously superior to those of a commercial platinum-carbon catalyst in an anion exchange membrane fuel cell anode hydroxide reaction.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional nanomaterial catalyst preparation technology, specifically relating to an Ir SA -Ni3N-t twinned nanosheet electrocatalysts, their preparation methods, and applications. Background Technology

[0002] Hydrogen energy is widely considered a promising energy carrier due to its high energy density and zero carbon emissions. Anion exchange membrane fuel cells (ACECs) have attracted significant attention due to their ability to achieve low-cost hydrogen conversion systems and their use of non-precious metal catalysts. However, the kinetics of the alkaline hydroxide reaction at the anode are two orders of magnitude slower under alkaline conditions than in acidic media, severely limiting the widespread industrialization and large-scale application of ACECs. Therefore, designing and developing low-cost, high-efficiency catalysts for the anode hydroxide reaction of ACECs based on abundant transition metal elements is of great importance.

[0003] In recent years, nickel-based catalysts, especially nickel-based nitrides (Ni3N) with superior adsorption performance for key reactants compared to pure nickel, have proven to be among the most promising and economically viable candidates. However, their activity in the hydrogenation reaction in alkaline electrolytes remains inferior to that of noble metals. In the alkaline hydrogenation reaction, hydroxyl groups, as the rate-limiting step, can be transferred to the catalyst surface via hydrogen bonding networks and adsorbed at the active sites, which is considered a key factor in hydrogen conversion kinetics. Therefore, designing nickel-based nitride catalysts with synergistic effects on hydroxyl transport and adsorption is crucial and highly anticipated to improve the performance of the alkaline hydrogenation reaction.

[0004] Nanotwinned structures exhibit high strength due to their ability to hinder dislocation slip. During electrocatalytic reactions, their zero-charge potential shifts significantly compared to single-crystal structures, resulting in a unique electric field distribution at the electrode-electrolyte interface. This change in interfacial electric field can alter the orientation of interfacial water molecules, thereby changing the behavior of transporting key intermediates via hydrogen bond networks during electrocatalysis. For example, *Angewandte Chemie International Edition* (63, e202407613, 2024) reported a strong interfacial electric field generated on the surface of a nickel-tungsten alloy catalyst, which resulted in reduced hydrogen bond network connectivity due to the rigidification of interfacial water molecules. Therefore, accurately constructing nanotwinned structures to study the transport and adsorption behavior of key reactants and further developing highly efficient hydrogen oxidation catalysts is of great significance.

[0005] However, in the anodic hydrogenation reaction of anion exchange membrane fuel cells, the preparation of twinned catalysts is exceptionally difficult due to the extremely high stacking fault energies of transition metal nitrides. To date, no research has reported a simple and rapid method for precisely constructing twinned structures of Ni3N nanomaterials, meaning that the current fuel cell anodic reaction cannot effectively utilize twinned catalysts to improve the energy conversion efficiency of anion exchange membrane fuel cells. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide an Ir SA -Ni3N-t twinned nanosheet electrocatalyst, its preparation method and application: Ni3N with twinned structure exhibits excellent catalytic activity, CO tolerance and long-term stability in the anodic hydrogenation process of anion exchange membrane fuel cell.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention improves the performance of alkaline hydroxide reaction by reducing the stacking fault energy and inducing the formation of twin structures at high temperature in the Ni3N lattice with Ir doping, thereby effectively regulating the adsorption and transfer of hydroxyl groups and the connectivity of hydrogen bond networks at the reaction interface.

[0008] To achieve the above-mentioned objectives of the present invention, the first objective of the present invention is to provide an Ir SA -Ni3N-t twinned nanosheet electrocatalyst, which has a significant twinned structure, enables high-activity and high-stability anode reaction applications in anion exchange membrane fuel cells.

[0009] The Ir SA -Ni3N-t nanosheets possess a significant nanotwinned structure, which can reduce the reaction interface potential, thereby weakening the interfacial electric field, reducing the rigidity of the interfacial water, and promoting the connection of the hydrogen bond network to enhance the hydroxyl transfer kinetics from the electrolyte to the catalyst surface, thus promoting the anode reaction activity and stability of anion exchange membrane fuel cells.

[0010] The second objective of this invention is to disclose an Ir SA Preparation method of Ni3N-t twinned nanosheet electrocatalyst: Nickel hydroxide nanosheets are dispersed in an iridium salt solution, and Ir-substituted nickel hydroxide nanosheets are obtained by a simple ion exchange method. The prepared Ir-substituted nickel hydroxide nanosheets are then subjected to high-temperature annealing in an ammonia atmosphere, followed by high-temperature nitriding in an ammonia atmosphere to prepare Ir. SA-Ni3N-t twinned nanosheets. The nickel hydroxide nanosheets were synthesized by a solvothermal method by dispersing nickel salt in an aqueous solution of pyrrolidone; the Ir-substituted nickel hydroxide nanosheets were prepared by dispersing nickel hydroxide in an aqueous solution, adding iridium salt, stirring, centrifuging, washing, and freeze-drying.

[0011] The Ir disclosed in this invention SA The preparation method of Ni3N-t twinned nanosheet electrocatalyst specifically includes the following steps: Step 1: Nickel salt was dispersed in an aqueous solution of pyrrolidone, and nickel hydroxide nanosheets were synthesized by a solvothermal method. Step 2: Disperse nickel hydroxide in an aqueous solution, add iridium salt, continue stirring, centrifuge, wash, and freeze-dry to obtain Ir-substituted nickel hydroxide nanosheets; Step 3: Ir-substituted nickel hydroxide nanosheets are annealed and nitrided under an ammonia atmosphere to prepare Ir. SA -Ni3N-t twinned nanosheets.

[0012] Preferably, the nickel salt is nickel nitrate, nickel sulfate, nickel chloride, or nickel acetylacetonate; the iridium salt is iridium chloride, potassium chloroiridate, or iridium acetate, and the iridium salt is added in the form of an aqueous solution; the pyrrolidone aqueous solution is one or more of 1-methyl-2-pyrrolidone, polyvinylpyrrolidone, and 2-pyrrolidone.

[0013] Preferably, in the pyrrolidone aqueous solution, the volume ratio of pyrrolidone to water is (0.5-11):1; and the molar ratio of nickel hydroxide to iridium salt is 1:(0.002-0.01).

[0014] Preferably, the Ir-substituted nickel hydroxide nanosheets are annealed and nitrided at 300-400 °C under an ammonia atmosphere to obtain Ir. SA -Ni3N-t twinned nanosheets.

[0015] Preferably, the ammonia flow rate is 100-150 sccm, and the mass of the Ir-substituted nickel hydroxide nanosheets is 40 mg-50 mg.

[0016] A third objective of this invention is to provide an Ir SA Application of Ni3N-t twinned nanosheet electrocatalyst in anodic hydrogenation of anion exchange membrane fuel cells.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The Ir disclosed in this invention SAThe Ni3N-t twinned nanosheet catalyst was obtained through a simple and rapid method via Ir single-atom-induced nickel nitride twinning strategy. It not only reduces the interfacial electric field by improving the connectivity of the hydrogen bond network and promotes the transfer of hydroxyl groups from the electrolyte to the catalyst surface, but also enhances the adsorption of hydroxyl groups on the catalyst surface and improves the conductivity to accelerate electron transport, thus playing a unique and significant role in alkaline hydrogenation.

[0018] The method disclosed in this invention, compared with the traditional design of hydrogen hydroxide electrocatalysts, has mild twin formation conditions and low synthesis cost. By using Ir atoms to reduce the stacking fault energy of nickel nitride, it is possible to achieve effective design of catalyst twin structures simply and quickly.

[0019] From an application perspective, the Ir obtained by this invention... SA -Ni3N-t twinned nanosheet catalysts can simultaneously achieve significant optimization of hydroxyl adsorption, transport, and hydrogen bond network connectivity during electrocatalysis, exhibiting excellent catalytic activity, CO tolerance, and long-term stability in the anodic hydrogen oxidation reaction of anion exchange membrane fuel cells. At an overpotential of 50 mV, Ir... SA -Ni3N-t twinned nanosheets exhibited a high efficiency of 2.99 mA / cm². 2 Its current density is higher than that of commercial platinum-carbon catalysts. Meanwhile, Ir... SA The Ni3N-t twinned nanosheet catalyst achieved a mass activity of 3.47 A / mg. Ir It improved by 4.7 times compared to commercial platinum-carbon catalysts, and compared to Ir SA The Ni3N-s single-crystal catalyst showed a 1.9-fold improvement, indicating that nanotwinned nitrides have the potential to replace noble metal catalysts. Furthermore, during a long alkaline hydroxide reaction lasting 10,000 cycles, Ir... SA The Ni3N-t twinned nanosheet catalyst exhibited excellent stability with no significant degradation. Furthermore, in the anodic hydrogenation catalytic reaction of an anion exchange membrane fuel cell using hydrogen mixed with 1000 ppm CO, Ir... SA The current density of the Ni3N-t twinned nanosheet catalyst decreased by only 5.6% compared to the high-purity hydrogen condition, while Ir SA The current density of the Ni3N-s single crystal catalyst and the commercial platinum-carbon catalyst decreased by 23.4% and 60.1%, respectively, reflecting the Ir SA -Ni3N-t twinned nanosheet catalysts exhibit excellent CO tolerance. Therefore, the resulting Ir... SA -Ni3N-t twinned nanosheet catalysts have great industrial application value in the anodic hydrogenation catalytic reaction of anion exchange membrane fuel cells. Attached Figure Description

[0020] Figure 1 Ir prepared in Example 1 SA Transmission electron microscope image of Ni3N-t nanosheets.

[0021] Figure 2 Ir prepared in Examples 1 and 2 SA -Ni3N-t twinned nanosheets and Ir SA Aberration-corrected high-angle annular dark-field scanning transmission electron microscope image of Ni3N-s single-crystal nanosheets; where a is Ir SA -Ni3N-t twinned nanosheets; b is Ir SA -Ni3N-s single crystal nanosheets.

[0022] Figure 3 Ir prepared in Example 1 SA - Scanning transmission electron microscopy (STEM) elemental analysis of Ni3N-t twinned nanosheets; where a is a high-angle annular dark-field image; b, c, and d are elemental distribution analyses.

[0023] Figure 4 Ir prepared in Examples 1 and 2 SA -Ni3N-t twinned nanosheets and Ir SA Comparison of X-ray diffraction patterns of Ni3N-s single-crystal nanosheets.

[0024] Figure 5 Ir prepared in Examples 1 and 2 SA -Ni3N-t twinned nanosheets and Ir SA X-ray absorption spectrum and Ni-Ni coordination number of Ni3N-s single crystal nanosheets; where a is the X-ray absorption spectrum and b is the Ni-Ni coordination number.

[0025] Figure 6 Ir prepared in Examples 1 and 2 SA -Ni3N-t twinned nanosheets and Ir SA In-situ infrared spectrum of Ni3N-s single-crystal nanosheets; where a is Ir SA -Ni3N-t twinned nanosheets; b is Ir SA -Ni3N-s single crystal nanosheets.

[0026] Figure 7 Ir prepared in Examples 1 and 2 SA -Ni3N-t twinned nanosheets and Ir SA Polarization curves of Ni3N-s single-crystal nanosheets and commercial platinum-carbon catalysts.

[0027] Figure 8 Ir prepared in Examples 1 and 2SA -Ni3N-t twinned nanosheets and Ir SA Comparison of the mass activity of Ni3N-s single-crystal nanosheets and commercial platinum-carbon catalysts at an overpotential of 50 mV.

[0028] Figure 9 Ir prepared in Example 1 SA A comparison of the polarization curves of -Ni3N-t twinned nanosheets before and after 10,000 cycles of testing.

[0029] Figure 10 Ir prepared in Example 1 SA -Ni3N-t twinned nanosheets and Ir SA A comparison of polarization curves of Ni3N-s single-crystal nanosheets and commercial platinum-carbon catalysts before and after the presence of CO. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] The present invention will now be described in further detail with reference to the accompanying drawings: Example 1 A type of Ir SA -Ni3N-t twinned nanosheet electrocatalyst and its preparation method, including the following steps: (1) Preparation of nickel hydroxide nanosheets At room temperature, 959.6 mg of nickel nitrate hexahydrate was added to 30.25 mL of 1-methyl-2-pyrrolidone and 2.75 mL of water and mixed solution. After stirring magnetically for 30 minutes, the mixture was homogeneous and reacted at 180 °C for 6 h. The resulting solution was centrifuged, washed and lyophilized with deionized water and ethanol to obtain nickel hydroxide nanosheets.

[0033] (2) Preparation of Ir-substituted nickel hydroxide nanosheets 46.3 mg of nickel hydroxide was dispersed in 15 mL of aqueous solution and mixed evenly after magnetic stirring for 30 minutes. Then, 1.5 mg of iridium trichloride was added and stirring was continued for 2 h. After centrifugation, washing and drying, Ir-substituted nickel hydroxide nanosheets were obtained.

[0034] (3) Ir SA Preparation of Ni3N-t twinned nanosheets The Ir-substituted nickel hydroxide nanosheets prepared above were subjected to annealing and nitriding at 355°C under an ammonia flow rate of 100-150 sccm to obtain Ir. SA -Ni3N-t twinned nanosheets.

[0035] Example 2 The difference between this embodiment and Embodiment 1 lies in the annealing and nitriding temperature under an ammonia atmosphere. Specifically, the annealing and nitriding temperature under an ammonia atmosphere is 335 °C, yielding Ir. SA -Ni3N-s single crystal nanosheets.

[0036] It can be seen that the only difference between the two embodiments is the synthesis temperature. The product obtained under low temperature conditions is a single crystal, while the product obtained under high temperature conditions is a twin crystal, and the twin crystal has better performance.

[0037] The structural tests are as follows: 1. Transmission electron microscopy and elemental analysis See results Figure 1 , Figure 1 Ir prepared in Example 1 SA Transmission electron microscopy image of Ni3N-t twinned nanosheets. The obtained product is a two-dimensional nanosheet structure, which is composed of multiple interconnected nanoparticles. Figure 2 Ir prepared for Examples 1 and 2 SA -Ni3N-t twinned nanosheets and Ir SA Aberration-corrected high-angle annular dark-field scanning transmission electron microscope images of Ni3N-s single-crystal nanosheets show the atomic arrangement of the Ni3N twin structure induced by Ir doping at 355 °C, and the atomic arrangement of the single-crystal structure formed at 335 °C. Figure 3 Ir prepared in Example 1 SA- Scanning transmission electron microscopy-elemental analysis diagram of Ni3N-t twinned nanosheets, in which Figure 3 In the image, 'a' represents a high-angle annular dark field image, 'b' represents the Ni elemental distribution analysis, 'c' represents the N elemental distribution analysis, and 'd' represents the Ir elemental distribution analysis. Figure 3 It can be seen that Ir, Ni and N elements are uniformly distributed throughout the region, confirming that Ir is uniformly distributed in the nanosheet.

[0038] 2. X-ray diffraction pattern.

[0039] Figure 4 Ir prepared in Examples 1 and 2 SA -Ni3N-t twinned nanosheets and Ir SA X-ray diffraction pattern of Ni3N-s single-crystal nanosheets. Figure 4 It can be seen that the obtained Ir SA -Ni3N-t twinned nanosheets and Ir SA -Ni3N-s single-crystal nanosheets are all hexagonal nickel nitride, with Ir existing in the form of single atoms and no diffraction peaks.

[0040] 3. X-ray absorption spectroscopy analysis Figure 5 Ir prepared in Examples 1 and 2 SA -Ni3N-t twinned nanosheets and Ir SA Extended X-ray absorption fine structure spectrum and corresponding coordination number diagram of Ni3N-s single-crystal nanosheets. Figure 5 It can be seen that, with Ir SA Compared to Ni3N-s single-crystal nanosheets, Ir SA The Ni-Ni coordination number of the -Ni3N-t twinned nanosheets decreased from 7.2 to 6.6, confirming that the formation of twin boundaries led to a reduction in the coordination environment of Ni atoms.

[0041] 4. In-situ infrared spectroscopy analysis Figure 6 Ir prepared in Examples 1 and 2 SA -Ni3N-t twinned nanosheets and Ir SA In-situ infrared spectrum of Ni3N-s single-crystal nanosheets. Figure 6 It can be seen that, with Ir SA Compared to Ni3N-s single-crystal nanosheets, Ir SA H2O from Ni3N-t twinned nanosheets gap The increase in the proportion of K·H₂O and the decrease in the proportion of Ir clearly indicate the evolution of interfacial water from the catalyst surface to the hydrogen bond interstitial region, thus confirming the presence of Ir. SA -Ni3N-t twinning enhances the connectivity of the hydrogen bond network, which is beneficial for the transfer of hydroxyl groups.

[0042] Performance testing and comparison for Ir SA -Ni3N-t twinned nanosheets and Ir SA Performance testing and comparison of Ni3N-s single-crystal nanosheets and commercial platinum-carbon catalysts in alkaline hydroxide reactions.

[0043] The Ir prepared in Examples 1 and 2 above SA -Ni3N-t twinned nanosheets and Ir SA The working electrode was fabricated using Ni3N-s single-crystal nanosheets and a commercially available platinum-carbon catalyst. Its catalytic activity, CO tolerance, and long-term stability in the alkaline hydroxide reaction were determined in a hydrogen-saturated 0.1 M potassium hydroxide solution. Tests were conducted at a scan rate of 1 mV / s and a rotation speed of 1600 rpm. The resulting curves are shown below. Figure 7 As shown. At an overpotential of 50 mV, Ir SA -Ni3N-t twinned nanosheets exhibited a high efficiency of 2.99 mA / cm². 2 Its current density is higher than that of commercial platinum-carbon catalysts. Figure 8 Showing Ir SA The Ni3N-t twinned nanosheet catalyst achieved a mass activity of 3.47 A / mg. Ir It improved by 4.7 times compared to commercial platinum-carbon catalysts, and compared to Ir SA The Ni3N-s single crystal catalyst showed a 1.9-fold improvement, indicating that nanotwinned nitrides have the potential to replace noble metal catalysts.

[0044] At the same time, such as Figure 9 As shown, during a 10,000-cycle alkaline hydroxide reaction, Ir SA The Ni3N-t twinned nanosheet catalyst exhibited excellent stability with no significant degradation. Furthermore, as... Figure 10 As shown, in the hydrogen anode hydroxide catalytic reaction of an anion exchange membrane fuel cell using hydrogen mixed with 1000 ppm CO, Ir SA The current density of the Ni3N-t twinned nanosheet catalyst showed only a slight decrease compared to high-purity hydrogen conditions, far lower than the performance degradation of commercial platinum-carbon catalysts, demonstrating Ir SA -Ni3N-t twinned nanosheet catalysts exhibit excellent CO tolerance. Therefore, the resulting Ir... SA The Ni3N-t twinned nanosheet catalyst exhibits excellent catalytic performance in the anodic hydrogenation catalytic reaction of anion exchange membrane fuel cells, and has significant potential for industrial application.

[0045] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A type of Ir SA -Ni3N-t twinned nanosheet electrocatalyst, characterized in that... The chemical composition of this electrocatalyst is Ir SA -Ni3N-t is a twinned structure formed by nitriding of Ir-substituted nickel hydroxide nanosheets under high-temperature annealing conditions.

2. An Ir according to claim 1 SA -Ni3N-t twinned nanosheet electrocatalyst, characterized in that... At an overpotential of 50 mV, Ir SA The current density of the Ni3N-t twinned nanosheets reached 2.99 mA / cm². 2 Mass activity reaches 3.47 A / mg Ir .

3. An Ir according to claim 1 SA -Ni3N-t twinned nanosheet electrocatalyst, characterized in that... During 10,000 cycles of alkaline hydroxide reaction, the Ir SA -Ni3N-t twinned nanosheet electrocatalyst showed no significant degradation.

4. An Ir according to any one of claims 1-3 SA The method for preparing Ni3N-t twinned nanosheet electrocatalysts is characterized by, include: Nickel hydroxide nanosheets were dispersed in an aqueous solution of iridium chloride, and Ir-substituted nickel hydroxide nanosheets were prepared by ion exchange. The Ir-substituted nickel hydroxide nanosheets were then subjected to high-temperature annealing under an ammonia atmosphere to obtain Ir... SA -Ni3N-t twinned nanosheets.

5. An Ir according to claim 4 SA The method for preparing Ni3N-t twinned nanosheet electrocatalysts is characterized by, Includes the following steps: Step 1: Nickel salt is dispersed in an aqueous solution of pyrrolidone, and nickel hydroxide nanosheets are synthesized by a solvothermal method; Step 2: Disperse nickel hydroxide nanosheets in an aqueous solution, add iridium salt, continue stirring, centrifuge, wash and freeze dry to obtain Ir-substituted nickel hydroxide nanosheets; Step 3: Ir-substituted nickel hydroxide nanosheets are annealed and nitrided in an ammonia atmosphere to prepare Ir-Ni3N twinned nanosheets.

6. An Ir according to claim 5 SA The method for preparing Ni3N-t twinned nanosheet electrocatalysts is characterized by, The nickel salt is nickel nitrate, nickel sulfate, nickel chloride, or nickel acetylacetonate; the iridium salt is iridium chloride, potassium chloroiridate, or iridium acetate, and the iridium salt is added in the form of an aqueous solution; the pyrrolidone aqueous solution is one or more of 1-methyl-2-pyrrolidone, polyvinylpyrrolidone, and 2-pyrrolidone.

7. An Ir according to claim 5 SA The method for preparing Ni3N-t twinned nanosheet electrocatalysts is characterized by, In step 1), the volume ratio of pyrrolidone to water in the pyrrolidone aqueous solution is (0.5-11):1; in step 2), the molar ratio of nickel hydroxide to iridium salt is 1:(0.002-0.01).

8. An Ir according to claim 5 SA The method for preparing Ni3N-t twinned nanosheet electrocatalysts is characterized by, In step 3), Ir-substituted nickel hydroxide nanosheets are placed in an ammonia atmosphere and annealed and nitrided at 300-400℃ to obtain Ir. SA -Ni3N-t twinned nanosheets.

9. An Ir according to claim 5 SA The method for preparing Ni3N-t twinned nanosheet electrocatalysts is characterized by, In step 3), the flow rate of the ammonia gas is 100-150 sccm.

10. An Ir according to any one of claims 1-3 SA Application of Ni3N-t twinned nanosheet electrocatalyst in the anodic hydrogenation reaction of anion exchange membrane fuel cell.

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