Morphology Construction Of Transition Metal Phosphide-based Carbon Materials And Their Electrocatalytic Hydrogen Evolution Reaction Performances

There is a variety of advantages in hydrogen and it occupies an important position in the social development in future.As a very promising technology,water electrolysis for hydrogen production has attracted extensive attention and in-depth research.The key part of the technique lies in the study of electrocatalyst.Currently,Platinum(Pt)-based materials are generally regarded as the state-of-the-art electrocatalysts,but the scarcity and high cost of Pt substantially hamper its widespread industrial application.Meanwhile,the transition metal materials have a good performance in water electrolysis for hydrogen production and there is an extremely wide space for their research.However,it remains an urgent and challenging task to improve their performance and stability.Therefore,regarding molybdenum phosphide composite carbon material(Mo P)sample as the experimental object,various conditions for optimizing the sample performance are studied.The main research contents of this paper are as follows:(1)By using graphitized carbon nitride(g-C₃N₄)as template,Mo P/C is prepared through self-pyrolysis phosphating process,in which Mo P present a nanometer rod-like structure.Based on the framework,the components are completely reduced to Mo P by means of high temperature reduction,and the sample morphology is modified.Mo P nano-rod connect to each other to weave into a network structure and integrate with curved multilayer carbon materials.Due to the hollow frame structure,the sample shows excellent performance in HER.The reversible hydrogen potential of the sample is 95 m V at the current density of 10 m A·cm^-2,and the Tafel slope is 85 m V·dec^-1.(2)Based on the Mo P nanorod structure,the synthesis route is optimized,and hierarchical hollow Mo P nanospheres anchored on N,P,S co-doped porous carbon(hs-Mo P/NPSC)is successfully prepared.Importantly,the porous shell of hollow nanosphere is actually well constructed by numbers of interwoven Mo P subunits,which is beneficial for exposing of surface active sites as much as possible.The specific surface area of the sample is up to 261 m²·g^-1,and the abundant pore structure can greatly promote the mass transport process and facilitate hydrogen desorption during the reaction.In addition,the heteroatom-enriched porous carbon networks can further reduce the electron/ion transfer resistance.As expected,the hs-Mo P/NPSC electrocatalyst exhibits an encouraging HER activity with a low overpotential of only70 m V at a current density of 10 m A·cm^-2,a small Tafel slope(87.2 m V·dec^-1)and long-term durability in alkaline media,outperforming most of reported Pt-free Mo-based electrocatalysts to date.It also performs well in acidic and neutral environments.In this paper,high-efficiency and stable transition metal/carbon-based composite electrocatalyst samples are successfully prepared through the structural design and composition control strategy.The samples exhibit excellent performance in the application of hydrogen evolution in water electrolysis.This work not only develops a non-noble metal-based catalyst for hydrogen evolution,but also provides new ideas for composite carbon materials in terms of structural design and morphology construction.