Design Of Co/Fe/Ni Based Hybrid Materials For Electrocatalytic Oxygen Evolution

Electrocatalysis water splitting is a promising energy storage/conversion system.The anodic oxygen evolution reaction（OER）of water splitting often press slowly kinetics which seriously impedes the efficiency and rate of hydrogen production.Traditional precious metal catalysts are limited to large-scale commercial application due to the scarcity,high cost and easy toxicosis.Transition metal hybrid materials have attracted much attention in the field of water splitting due to their advantages of low cost,high stability and abundant electrocatalytic active sites.In this paper,hybrid materials were constructed by treating hypoxanthine and/or zoledronic acid with Co²⁺,Fe²⁺,Ni²⁺and Zn²⁺,and the OER electrocatalytic performance were tested under alkaline conditions.The OER performances were optimized by bimetal and/or trimetal doping to slightly change the local electronic structure of metal centers.The main research contents are as follows:（1）Co₂（μ₂-OH）₂（HSO₄）₂（H₂Pxt）₂·H₂O（Co₂-H₂Pxt）was successfully constructed by one-step solvethermal method using Co SO₄·7H₂O,H₂Pxt,H₂O and acetonitrile as raw materials.On this basis,four isomorphic bimetallic hybrid materials Co_2-xFe_x-H₂Pxt were obtained by doping Fe²⁺.The OER performance of bitmetal is better than that of single metal in alkaline condition.Co_1.43Fe_0.57-H₂Pxt exhibits excellent OER performance with a low overpotentials（296 m V）at a current density of 10 m A cm^-2and a Tafel slope of 62.6 m V dec^-1.The current density remains 85%after 24 h catalysis.XPS showed that the peak value of Co 2p moved to the direction of the positive binding energy,indicating that the incorporation of Fe ions changed the local electronic structure.The improved OER performance may be attributed to Co/Fe synergies.（2）Bimetal Zn_0.7Ni_2.3-NPBS,Zn_2.4Ni_0.6-NPBS,Zn_2.8Ni_0.2-NPBS,Zn_2.5Fe_0.5-NPBS hybrid material catalysts were prepared by hydrothermal method using phosphonic acid（Zoledronic acid）.The overpotential of Zn_2.5Fe_0.5-NPBS was 295 m V and Tafel slope was83.0 m V dec^-1in alkaline electrolyte solution.In order to further improve its oxygen evolution performance,Ni²⁺and Fe²⁺were simultaneously introduced to obtain Zn_2.3Ni_0.5Fe_0.2-NPBS and Zn_2.1Ni_0.6Fe_0.3-NPBS.Among which,the overpotential of Zn_2.3Ni_0.5Fe_0.2-NPBS at the current density of 10 m A cm^-2is 292 m V,the slope of Tafel is74.4 m V dec^-1,and the electrocatalytic activity of Zn_2.3Ni_0.5Fe_0.2-NPBS is still high at 90000s.SEM images show that the morphology of Zn_2.3Ni_0.5Fe_0.2-NPBS changes and its size decrease.The improvement of OER performance may be due to the synergisit effect among Zn/Ni/Fe.