Preparation And Electrocatalytic Performance Of Iron Series Metal Phosphide Composite Materials

As an energy carrier,hydrogen has the characteristics of high energy density and environmental friendliness,and is considered one of the ideal alternatives to fossil fuels.Electrochemical water decomposition is considered as a simple,green and feasible way to produce hydrogen.Hydrogen production by electrolysis of water depends largely on the oxygen evolution reaction（OER）of the anode.Much research has focused on the development of efficient electrocatalysts to reduce the activation energy of reactions.Because OER involves a four-electron transfer process,it has the disadvantages of slow kinetics and high thermodynamic energy barrier,resulting in electrochemical water splitting at voltages well over 1.23 V.To date,the most effective electrochemical water splitting catalysts are still precious metal materials based on Pt,Ru and Ir.However,due to the scarcity of resources,these precious metal materials do not take advantage of industrial use.Therefore,the search for suitable,efficient,cheap,stable and abundant electrochemical hydrolysis materials is essential for large-scale commercialization of electrolytic hydrogen production on a global scale.Transition metal-based electrocatalysts are considered promising alternatives to noble metal-based electrocatalysts.In addition,various thermodynamically more favorable small molecule oxidation reactions have been designed to replace the slow OER of the anode to achieve efficient hydrogen production.The main research contents are given as follows:（1）Using ZIF-67 cubes（NCs）as templates,a hollow porous Co-based trimetal phosphating nanobox（Co Ni Fe P@C NBs）was synthesized by chemical etching,cation introduction and subsequent high-temperature cracking process.This catalyst is a nanoparticle confined to the carbon layer of the nanobox.Benefiting from the regulation of electron density by trimetallic composition and the exposure of more active sites by the porous hollow structure,the optimized trimetallic Co Ni Fe P@C NBs exhibited excellent OER electrocatalytic performance and excellent stability.Under the test conditions of 1 M KOH solution,the overpotential required to achieve a current density of 10 m A cm^-2 is only 260 m V,and the Tafel slope is 65.5 m V dec^-1.（2）Dandelion-like Co Ni P@Co Fe P nanoneedle arrays were prepared by phosphating precursor Ni Co-CHH@PBA.The prepared Co Ni P@Co Fe P exhibited excellent catalytic activity of OER and hydrogen evolution reaction（HER）,which may be due to a rational combination of metal phosphides.In addition,the catalyst also has a good effect on hydrazineborane oxidation（HBOR）.When HBOR replaces slow OER,HBOR requires a lower voltage at current density,allowing this strategy to produce hydrogen by electrolysis more energy-saving.The dual-electrode electrolyzer only needs a small cell voltage of 0.078 V to achieve the current densities of 10 m A cm^-2,which is 1.48 V less than the overall water splitting system.This indicates that the electrolyzer has great potential for energy-saving and high-efficient hydrogen production compared with traditional water electrolysis.