Microstructural Control Of FeV Bimetallic-based Electrocatalysts And Their Application In Water Splitting

With the intensification of global energy crisis and environmental pollution,it is imperative to explore the development of new renewable energy and energy conversion technologies.Electrocatalytic water splitting has the advantages of relatively simple operating conditions,high conversion efficiency,easy control of the reaction process,and the high purity of hydrogen obtained by this technology,clean and pollution-free,which is regarded as one of the most ideal and effective technologies for the preparation of new energy sources.However,electrocatalytic reactions usually involve multiple electron transfer processes resulting in slow kinetics,and many catalysts still require high potentials for the reactions to occur.Therefore,the nature of the catalyst becomes an important factor affecting the performance of electrocatalytic decomposition of water.In recent years,transition metal-based electrocatalysts,due to their wide source of raw materials,abundant species and unique electronic geometry,have received much attention in the field of Electrocatalytic water splitting.Moreover,by constructing dual transition metal-based catalysts,the catalyst reaction kinetic characteristics can be changed by using the synergistic interaction of electrons between metals to achieve a substantial improvement of Electrocatalytic water splitting performance.Therefore,FeV dual transition metal-based materials were selected in this work,and FeV oxide nanodisc and nanosheet materials were prepared by the solvothermal method,and further surface amorphization and nitrogen anion doping were performed to effectively modulate the microstructure of the two FeV oxides,and a series of electrocatalyst materials with high catalytic activity were obtained.The specific studies are as follows.(1)The effect of surface amorphization on the electrocatalytic performance of FeV oxide nanodiscs(FeV)was investigated.The FeV nanodiscs with Fe2O3-like crystalline phase structure were firstly prepared using hydrothermal method and further annealed under N2 and air conditions sequentially to finally generate FVO nanodiscs with amorphous surface structure(labeled as Am/FVO).The electrochemical tests showed that the potential of the electrocatalyst Am/FVO at a current density of 20 mA/cm2 was 1.49 V vs.RHE(relative to a standard hydrogen electrode),the Tafel slope was 56.6 mV/dec,and the electrochemical specific surface was 10.9 mF/cm2,and the results showed that the oxygen production performance of Am/FVO was superior to that of the untreated FVO and commercial The stability test also showed that the electrocatalytic performance of the material could be maintained stably for more than 48 h,and its structure and performance remained unchanged after 1000 cycles of testing.Based on X-ray photoelectron spectroscopy(XPS)analysis,it is concluded that during the annealing process,more oxygen vacancies are formed on the surface of Am/FVO,which can effectively modulate the surface electronic structure and thus increase the material’s own electrical conductivity.In addition,Am/FVO generates more Fe3+ and V5+,which in turn enhances its oxidation ability and leads to further improvement of OER performance,and the valence band spectrum also verifies this result.(2)The effect of N anion doping on the performance of FeV oxide nanosheets(FeV)for Electrocatalytic water splitting was investigated.The nanosheet FeV electrocatalysts were firstly prepared by water bath method and then treated with ammonia,and N anions were found to be doped into the FeV nanosheet structure(labeled as N-FeV).Electrochemical hydrogen/oxygen production performance tests revealed that the hydrogen production potential of N-FeV at 20 mA/cm2 current density was 0.273 V vs.RHE,Tafel slope 109.7 mV/dec,and electrochemical specific surface was 1.93 mF/cm2;the oxygen production potential at 20 mA/cm2 current density was 1.45 V vs.RHE,Tafel slope of 48.61 mV/dec,and electrochemical specific surface of 6.6 mF/cm2.The results of the study show that.Compared with the untreated FeV material,N-FeV obtained higher hydrogen-and oxygen-producing activities and stability under alkaline conditions.In addition,the potential of N-FeV was found to be 1.70 V vs.RHE at a current density of 10 mA/cm2 and its performance was able to be maintained for more than 48 h by the total water dissolution performance test.The results indicate that the improved performance of this catalyst is attributed to the N anion induced effect,which reconFig.s the surface chemical structure of FeV,not only to generate more active sites,but also to effectively modulate its surface electronic structure and promote rapid electron charge migration for hydrogen and oxygen precipitation reactions.