Synthesis Of Cobalt-Nickel Based Nitrides And Oxides Catalysts And Study On Their Application To Photo-electrocatalytic Hydrogen Production

Energy depletion and environmental pollution are major problems brought by the rapid development of contemporary society and economy,and one of the means to solve the problems is the development and utilization of renewable energy,among which hydrogen energy is one of the best choices.In order to improve the efficiency of hydrogen production,the development and utilization of transition metals and their compounds is a good choice.Therefore,it is very important to explore excellent transition metal catalysts suitable for electrocatalytic and photocatalytic decomposition of water to hydrogen.In this paper,through the exploration of Co-Ni bimetallic catalysts,its structural components are designed in order to reduce the electrolytic water barrier and improve the activity of electrocatalytic reaction.Based on the above concepts,a three-dimensional porous cobalt-nickel compound catalysts grown on NF was prepared and used for electrocatalytic water decomposition to test its physical properties and electrocatalytic performance.Then a photocatalyst（Bi VO₄）film was prepared,and the cobalt-nickel catalysts were loaded on the Bi VO₄film as co-catalysts,and their physical properties and photocatalytic performance were tested.The main research contents and conclusions are as follows:The first part of this paper is to prepare cobalt-nickel electrocatalysts and test their physical properties and electrocatalytic performance.The precursors of different cobalt-nickel components were prepared on nickel foam substrates by hydrothermal synthesis,and then calcined at high temperature,the corresponding cobalt-nickel oxides and nitrides were obtained in the atmosphere of air and ammonia,respectively,and their morphology,structure,element physical characterization and OER electrochemical properties were tested,thus the structure composition and electrochemical properties of cobalt-nickel catalyst samples were analyzed in depth.The morphology is quite different,when the composition of nickel element is large,the oxide shows flake structure,the nitride shows bubble-like structure,while when the composition of cobalt element is large,oxide and nitride are needle-like structure.In 1.0 M KOH solution,when the current density measured by LSV reaches 20m A/cm~2,the overpotentials of composite oxides and nitrides with Co:Ni ratio 0.7:0.3are the smallest,which are 303 m V and 268 m V,respectively,while for single metal oxides of Co and Ni,the overpotentials are 346 m V and 401 m V,and the overpotentials of nitrides are 307 m V and 374 m V,respectively.It can be found that on the one hand,the electrocatalytic activity of bimetallic composite catalysts is much higher than that of single metal catalysts,on the other hand,the electrocatalytic activity of nitrides is much higher than that of oxides.The second part of this paper is to load cobalt-nickel cocatalysts on Bi VO₄thin films and test their physical properties and photocatalytic properties.Bi VO₄thin films were prepared by electrochemical deposition method and calcination method as photocatalysts,and then cobalt-nickel catalysts were used as co-catalysts.The structure and photoelectrochemical properties of the loaded Bi VO₄photoanodes were analyzed by SEM,XRD,XPS and other physical characterization methods and photoelectrochemical performance tests.In the photoelectrochemical test,under the voltage of 1.23 V_RHE,the photocurrent density of pure Bi VO₄samples in LSV test can only reach 0.56 m A/cm~2,while the photocurrent densities of cobalt and nickel monometallic nitride samples,cobalt-nickel bimetallic oxides and nitrides（Co-Ni ratio 0.7 to 0.3）are 1.22 m A/cm~2,0.61 m A/cm~2,1.09 m A/cm~2and 2.32 m A/cm~2,respectively.Then the law of LSV is verified by EIS,MS and other tests.It can be found that on the one hand,the loading of the co-catalyst has a favorable effect on the water decomposition process of the Bi VO₄photoanode.The reason is that the generation of the co-catalyst layer reduces the recombination of photogenerated electron hole pairs in Bi VO₄and speeds up the interfacial reaction rate.On the other hand,the effect of different co-catalysts loading is also different,and the law is consistent with the electrocatalytic process,that is,cobalt-nickel bimetallic nitrides as co-catalysts loading effect is the best,the photoelectrochemical performance is the best.Figure[60]table[4]reference[110]...