Preparation Of Cobalt And Iron-based Phosphides (Sulfides) Nanostructure By Precursor Method And Their Electrocatalytic Research

Hydrogen(H₂)is a clean energy carrier with high energy density,abundant reserves and zero carbon emissions.It is also an important chemical raw material.The development of efficient and clean hydrogen production technology has become the key to the future development of hydrogen energy.The electrocatalytic water decomposition technology includes cathode hydrogen evolution reaction(HER)and anodic oxygen evolution reaction(OER),which uses water as a raw material,electric energy as a driving force,and has the characteristics of green and high-efficiency hydrogen production.Both OER and HER processes require high-efficiency catalysts to reduce overpotentials,which in turn reduces energy consumption and hydrogen production costs.It is well known that noble metal materials such as Ir O₂,Ru O₂ and Pt have excellent electrocatalytic activity,but they are rare in storage and expensive,which severely limits the large-scale application of electrolyzed water technology.Therefore,the exploitation of abundant and efficient electrocatalyst materials is the key to promoting the development of electrolyzed water technology.This paper aims to design and develop low-cost,green,and efficient electrocatalysts using inexpensive,rich transition metals and non-metals.In this paper,a series of nano-structures with different compositions as precursors were used to prepare a series of excellent cobalt-iron-based phosphides(sulfides)electrocatalytic materials by metal doping,ion co-deposition and high temperature atmosphere treatment.The mechanism and structure-effect relationship of hydrogen evolution and oxygen evolution performance were analyzed and discussed.The main work is as follows:(1)Fe-Co₉S₈ nanospheres upported on nickel foam were prepared by optimizing hydrothermal method.The Fe doping optimizes the size structure of Co₉S₈ nanospheres,exposes more active sites,and enhances the conductivity and proton conduction rate of Co₉S₈.At the same time,the synergistic effect of iron and cobalt ions can increase the OER intrinsic activity and stability of the catalyst.(2)P-S-Ni Fe NCs with excellent OER activities and stability were prepared by optimizing the conditions and sequence of gas phase phosphorization and sulfuration with the bimetallic nickel-iron nanocubes(Ni Fe NCs)as precursors.The surface of C-doped P-S-Ni Fe NCs is rich in defect sites,which is the intrinsic reason for the improvement of catalyst performance.(3)P-Ni Fe-800 NPs with abundant defect sites were prepared by optimizing the calcination temperature and gas phase phosphorization under argon and using Ni Fe nanocube as precursor.P-Ni Fe-800 NPs have excellent catalytic activities,bigger specific surface area and smaller tafel slope.And the P-Ni Fe-800 NPs require only a 270.1 m V overpotential to achieve a current density of 10 m A cm^-2.This work provides a simple and easy method for the preparation of iron-based bimetallic phosphide catalysts.(4)In situ construction of surface defects of carbon-doped cobalt-iron-based ternary metal phosphide nanocubes(P-Co_0.9Ni_0.9Fe_1.2NCs)by precursor method and high temperature gas phase phosphorization under argon.P-Co_0.9Ni_0.9Fe_1.2NCs have excellent HER and OER properties under alkaline conditions.The rough surface,rich surface defect sites,unique nanocube structure and high conductivity are the main reasons for the improved performance of P-Co_0.9N_i0.9Fe_1.2 NCs after high temperature carbonization.