The Preparation Of Cobalt-based Phosphates And Their Derivative Micro-nano Materials And Their Oxygen Evolution Reaction Research

The phosphoric groups in transition metal phosphate have strong coordination,which can stabilize the intermediate state of transition metal,thus ensuring the effective REDOX reaction of transition metal center.In addition,phosphate groups have multiple orientations and can induce multiple crystal structures,making metal phosphates an ideal platform for designing oxygen evolution reaction catalysts with specific structures.In this paper,cobalt salt is selected as the metal source,a series of cobalt phosphate materials are prepared by changing the calcination conditions,and the obtained materials are used as catalysts in electrocatalytic reactions.The experimental results show that a series of samples can be prepared in large quantities,and the practical applicability of such materials is proved by studying the relationship between different materials and electrocatalytic performance.At the same time,it provides an idea for us to find electrocatalyst materials with better performance.The main research contents and results of this paper are as follows:1.The application of amorphous cobalt phosphate nanosheets derived from 2D Co-MOF in electrocatalytic oxygen evolution.2D Co-MOF was synthesized using cobalt acetylacetonate as the metal source and phenyl phosphate as the ligand.A-CoPOx is obtained by calcining 2D Co-MOF.A-CoPOx has good electrochemical performance in alkaline electrolyte,with a working potential of 1.508 V.In this work,the pyrolysis temperature plays a key role.By changing the calcination temperature,the chemical composition and unique structure of 2D Co-MOF also change.A-CoPOx retains the flake morphology of 2D Co-MOF,and the surface has a uniform pore distribution.The sheet structure can expose more metal atoms,and these unsaturated coordinated metal centers play an important role in electrocatalysis.The porous structure increases the distribution of active centers and promotes the diffusion of electrolyte.2.The preparation of CoPO/C derived from Co-MOF and its application in electrocatalytic oxygen evolution.Using Co-MOF as a template,a composite material of carbon and cobalt phosphate(CoPO/C)is prepared by a simple carbonization.The combination of carbon and cobalt phosphate enhances the rapid charge transfer,transport and good electrical conductivity between the material and the electrolyte.These special physical and chemical characteristics make CoPO/C show relatively excellent electrochemical performance in the OER test(at 10 mA cm-2,the overpotential is only 345 mV).3.General synthesis of nitrogen-doped transition metal phosphates(M=Co2+,Mn2+,Ni2+,Cu2+)and the application of A-NCoPO in electrocatalytic oxygen precipitation.A simple chemical precipitation method was used to synthesize transition metal ammonium phosphate(NH4MPO4·H2O).The corresponding nitrogen-doped metal phosphate(N-MPO)is obtained by controlled calcination of metal ammonium phosphate.We successfully synthesized N-CoPO,N-MnPO,N-NiPO and N-CuPO through this simple synthesis method.Among them,amorphous N-CoPO(A-NCoPO)has abundant active centers,porous surface and good durability,making it a promising OER electrocatalyst.Compared with ordinary cobalt phosphate materials,A-NCoPO has a lower reversible oxygen electrode index(1.411 V)and more significant electrochemical activity.This simple nitrogen doping method provides an idea for the synthesis of other nitrogen doped materials,in order to find new materials with better performance.