Preparation And Properties Of 3D Self-supporting Structure Electrocatalytic Hydrogen Production Materials

In recent years,with the excessive exploitation and utilization of fossil fuels,resource exhaustion and environmental problems become more and more acute.Developing clean and sustainable renewable energy is the most effective way to solve these problems.As a result of its high calorific value and zero pollution from combustion products,hydrogen is an ideal clean fuel for sustainable energy applications and is considered as an ideal alternative to fossil fuels.At present,all countries in the world are committed to the development of hydrogen energy technology,among which overall water splitting hydrogen production is one of the most important methods of hydrogen production technology.Hydrogen production by overall water splitting is one of the most important methods of hydrogen production,and hydrogen production technology in industry is mainly carried out by hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）two half-cell reactions.In fact,an effective catalyst is needed to initiate two reactions in the overall water splitting reaction.Platinum group of metals are highly efficient catalyst for HER,and the benchmark catalyst for OER is Ir/Ru based compound.However,the high cost and scarcity of these precious metals limit their widespread use.Therefore,the development of non-noble metal electrolysis water catalyst with high activity and stability is very important,and it is also one of the main research directions of current researchers.In this paper,Ni based multistage composite materials as the research object,in order to improve the catalytic performance of water electrolysis for the purpose of research.3D core-shell structure electrocatalysts with high catalytic activity and high stability and large specific surface area were successfully prepared by means of interface engineering carrier composite macro multistage structure design and surface micro control.Through the simple hydrogen-thermal reduction reaction was used to transform NiMoO₄ into MoNi/NiMoO_x nanowires with MoNi alloy nanoparticles and their metal oxide co-existing structure,which greatly improved the electron transport capacity of the nanowire structure.Subsequently,NiFelayered dihydroxide（NiFeLDH）nanosheets were reasonably modified on the surface of MoNi/NiMoO_x nanowires by electrodeposition,3D core-shell MoNi/NiMoO_x@NiFeLDH catalysts were prepared.The 3D core-shell structure Co@Ni₂P/NF catalyst with Ni₂P nanosheets coated with Co（OH）₂ nanowires was synthesized by the two-step hydrothermal synthesis method and transformed into transition metal phosphide by phosphine thermal annealing.The results show that the low resistivity of MoNi/NiMoO_x nanowires in the core provides a fast charge transfer channel for MoNi/NiMoO_x@NiFeLDH catalyst,and the ultrathin NiFeLDH nanosheets provided abundant exposure defects and catalytic active sites for the MoNi/NiMoO_x@NiFeLDH nanosheets catalyst.The overpotential of MoNi/NiMoO_x nanowire arrays in hydrogen evolution reaction is 134 mV overpotential at 100 mA·cm^-2 current density,respectively.According to the Volmer-Heyrovsky mechanism,the small Tafel slope of MoNi/NiMoO_x nanowire arrays(81.0mV·dce^-1)follow the Volmer–Heyrovsky pathway,indicating a favorable HER reaction kinetics for the MoNi/NiMoO_x catalyst.In the oxygen evolution reaction,MoNi/NiMoOx@NiFeLDH catalyst requires only 278 mV overpotential at 100mA·cm^-2 current density,and Tafel slope is only 44.7 mV·dce^-1.The catalytic activity and durability of Co@Ni₂P/NF catalyst were greatly improved by phosphine thermal annealing to transition metal phosphide.Co@Ni₂P/NF catalyst can be used as a bifunctional catalyst for overall water splitting,achieving a current density of 100mA·cm^-2 with a voltage of 1.72 V,even superior to the benchmark of IrO₂（+）//Pt/C（-）.The 3D core-shell structure design enables the two catalysts to have good hydrophilicity and show fast contact wetting time in different electrolyte solutions.It solves the problems of gas aggregation on the surface of electrocatalytic material and low electrocatalytic activity in the process of water electrolysis,which has reference and guidance value for the design of 3D core-shell structure overall water splitting catalyst.