Synthesis Of MoP-NC Performance In Electrochemical Hydrogen Evolution

Energy problems often determine the direction of the world economy.However,with the large amount of energy consumed,the environmental pollution and other problems caused by it have gradually emerged.Therefore,finding a renewable and environmentally-friendly clean energy has been a hot topic in recent years.Hydrogen has gradually attracted people's attention as a high-density clean energy source.For this reason,researchers have also explored it for a long time.One of them is the production of hydrogen by electrolysis of water.Nevertheless,the efficiency of the traditional electrolysis of water to produce hydrogen is not very satisfactory.Fortunately,the efficiency of hydrogen production has gradually increased in recent years with the introduction of electrocatalysts.Whereas it still faces a problem.High-performance electrocatalytic hydrogen evolution catalysts are mainly derived from precious metals Pt,Pd and their derived materials.However,such materials themselves are scarce and costly,which severely hinders the development and application of such catalysts.Molybdenum phosphide and cobalt phosphide in transition metal phosphide can be said to be promising non-precious metal catalysts for hydrogen evolution reaction(HER),and modified cobalt phosphide can even obtain additional oxygen evolution reaction(OER)performance.However,their unsatisfactory stability and conductivity in alkaline environments have dragged their development.Taking this as a mechanism,this article aims to improve their electrocatalytic performance in alkaline environment by co-doping N and C and Metal-Organic Frameworks(MOFs)to modify molybdenum phosphide and cobalt phosphide.The main research contents are as follows:(1)The exploration based on carbon-based molybdenum phosphide was synthesized by a simple and effective two-step synthesis method.Firstly,ammonium molybdate tetrahydrate and ammonium dihydrogen phosphate were used as raw materials,and urea was used as a carbon source to physically compound them.Subsequently,they were thermally decomposed to introduce a carbon source into the molybdenum phosphide system,and N,C co-doped MoP(MoP-NC)nanoparticles were successfully synthesized.Then the SEM and TEM scanning of the synthesized samples were performed to determine the morphology and structure,and the element and functional group composition of the samples were characterized by XRD and XPS.Various parameters of the electrochemical performance of the sample can be obtained by rotating the disk electrode and the electrochemical workstation.The results show that in this system,urea participates in the synthesis reaction with an excellent carbon-nitrogen ratio to further improve the electrocatalytic performance of MoP-NC composites.Therefore,this material has excellent HER electrocatalytic activity and stability.It only needs 131 mV overpotential in 1 M KOH to achieve a current density of 10 mA cm-2,and shows insignificant performance after 1000 CV cycles decline.(2)Zeolitic Imidazolate Frameworks(ZIFs)are commonly used to synthesize MOFs.The exploration of cobalt phosphide based on MOFs is to further explore the dual-functional catalytic activity(HER and OER)of transition metal phosphides based on molybdenum phosphide.Cobalt nitrate and 2-methylimidazole were used to synthesize ZIF-67 based on MOFs and containing Co.The ZIF-67 was then thermally decomposed with a composite carbon source(melamine)to obtain an intermediate product.Finally,Co-NC/CoP-NC was successfully synthesized by phosphating the intermediate product.Then the morphology,structure,chemical composition and characterization of the synthesized samples were analyzed.The results show that the HER and OER electrocatalytic performance of the samples prepared by phosphating ZIF-67 containing a composite carbon source to participate in pyrolysis are better than those of ZIF-67 that is directly pyrolyzed in an alkaline test environment.This is because the gas generated during the thermal decomposition of melamine further contributed to the hollow structure of the prepared sample.Therefore,in HER performance,this sample requires 282 mV overpotential in 1 M KOH to achieve a current density of 10 mA cm-2.In terms of OER performance,the sample requires only 1.73 V overpotential in 1 M KOH to achieve a current density of 10 mA cm-2.However,the stability of this sample after 1000 CV cycles is not very satisfactory and needs further improvement.Figure 17 table 3 reference 121...