Preparation Of Bifunctionl Transition Metal Nanomaterials On Carbon Materials And Application Of Electrolytic Water Catalytic Performance

Nowadays,the large-scale combustion of fossil fuels has caused the energy crisis and environmental pollution problems.The development of clean and renewable energy has become an important challenge in the 21st century.As a clean and renewable energy source,the development of hydrogen energy has become a focus of current research.In hydrogen production technology,electrolyzed water is one of the most promising methods for producing high-purity hydrogen energy.Therefore,the reaction rate of hydrogen evolution reaction?HER?,oxygen evolution reaction?OER?and oxygen reduction reaction?ORR?inevitably determines the efficiency of energy conversion.In general,catalysts based on noble metals?Pt,Ir,and Ru?can effectively reduce the activation energy and provide a faster reaction rate.However,due to scarcity and high cost,it is difficult to apply on a large scale.Due to the unique properties of transition metal compounds?TMC?,such as low cost,rich content,high electrochemical activity and long-term stability,a lot of researches have been conducted on their hydrolytic electrocatalytic performance in recent years.In this paper,transition metal phosphides,bimetal sulfides and bimetal selenides combined with carbon materials are studied,and the catalytic performance of their electrolytic water is studied.The main work is as follows:1.Mesoporous carbon-coated nickel phosphide?NiP?nanoparticles with the hexagonal structure were successfully synthesized by thermal decomposition at500°C under N₂/H₂?95:5?atmosphere.The NiP/C hybrid exhibits excellent OER/ORR activity.At the OER current density of 10 m A cm^-2,the overpotential is0.26 V,and its Tafel slope is 43 mV dec^-1.In addition,the material has the highest ORR catalytic activity at 1600 rpm,and the half-wave potential is 0.82 V,the diffusion limit current density?J_L?is 5.10 mA cm^-2.And after 25 hours of current polarization,the catalyst still maintains a fairly stable OER/ORR catalytic current.This cost-effective strategy opens a new path for the future development of OER/ORR dual-function catalysts for industrial applications.2.The WS₂@Co₃S₄ NW/CC composite with a typical core-shell nanostructure was synthesized in one step by solvothermal reaction with?NH₄?₂WS₄ using Co₃O₄NW/CC as the substrate.This material has highly efficient HER/OER catalytic activity.In 0.5 M H₂SO₄ electrolyte,when the HER current density is 10 mA cm^-2,the overpotential is 89.5 mV and the Tafel slope is 45.6 mV dec^-1,the HER catalytic activity is close to Pt/C catalyst.The catalysts show a high OER capability in 1 M KOH solution with an overpotential as small as 270 mV,and they offer an OER current density of 10 mA cm^-22 at a low Tafel slope of 52.4 m V dec^-1.The excellent catalytic performance of WS₂@Co₃S₄ NW/CC is mainly due to its large electrochemical surface area and conductivity.The long-term catalytic stability is of great significance for the practical application of water splitting.After a long-term current polarization of the catalyst,the HER/OER catalytic activity has not changed significantly.Therefore,the highly efficient WS₂@Co₃S₄ NW/CC bi-function catalyst is expected to be applied to large-scale electrolysis of water to produce hydrogen energy.3.MoSe₂@CoSe₂ nanowire composites were synthesized by chemical vapor deposition using selenium powder and molybdenum oxide powder as growth precursors and Co₃O₄ nanowires grown on carbon cloth as a substrate.Electrochemical measurements have confirmed that MoSe₂@CoSe₂ NW/CC has excellent HER/OER catalytic performance in 1 M KOH electrolyte.When the HER current density is 10 mA cm^-2,the overpotential is 73.2 mV and the Tafel slope is 41.1mV dec^-1.And it can generate an OER current density of 10 mA cm^-22 at the overpotential of 260 mV with a low Tafel slope of 41.5 mV dec^-1.During the whole electrochemical performance test,MoSe₂@CoSe₂ NW/CC has stronger HER/OER catalytic activity than the bare CoSe₂ NW/CC and MoSe₂ NS/CC catalysts.In addition,the HER/OER catalytic activity of MoSe₂@CoSe₂ NW/CC did not significantly decrease after 10 hours of polarization.This is mainly due to the core-shell nanostructure of MoSe₂@CoSe₂ NW/CC composites that can promote the rapid transfer of charge,and the synergistic effects between the Mo and Co ions in the material.