Study On Modification Of Bimetallic MOF And Oxygen Evolution Performance In Water Electrolysis

Clean hydrogen energy has become one of the most popular new sources of energy as renewable energy sources run out.One of the ways to improve the efficiency of hydrogen production is to increase the rate of oxygen evolution in electrolytic water.Noble metal base is a good catalyst for electrolytic water oxygen evolution reaction,but its rarity and high cost limit the industrialization of hydrogen production by electrolytic water,so it is necessary to develop low price and excellent catalytic performance of electrolytic water oxygen evolution catalyst.Metal-organic skeleton（MOF）has become a hot topic in oxygen evolution catalyst research due to its advantages of ultra-high surface area and low density large pore volume.In this paper,a composite electrocatalyst with good electrocatalytic performance was synthesized by modifying the MOF-based catalyst,and applied to the electrolytic water oxygen evolution reaction.XRD,FT-IR,SEM,TG,BET,LSV,CV,and EIS were used to analyze and evaluate the composite electrocatalyst.The specific research content of this paper is as follows:（1）Three kinds of electrocatalysts,NiCo-MOF,Cu Co-MOF and Cu Ni-MOF,were prepared by one-step hydrothermal method by using low price and excellent performance transition metals,Co,Ni and Cu,as the metal center of MOF-74.The synergistic effect of two different metal ions makes the three MOF catalysts show different electrocatalytic performance.In general,the MOF catalysts with two metal combinations show better electrocatalytic performance than the MOF with a single metal center in alkaline solution,in which the synergistic effect of Co and Ni is the most obvious.The optimal catalyst is NiCo-MOF.Theη₁₀(overpotential when the current density is 10 mA·cm^-2)of NiCo-MOF in 1M KOH is 420 mV,and the slope of Tafel is 89mv·dec^-1,which shows that Ni and Co have better synergy in MOF-74.（2）The Fe（OH）₃/NiCo-MOF binary composite catalyst was prepared by"iron-phenol"reaction using a simple stirring method.The mechanism of oxygen evolution reaction catalyzed by composite catalyst was studied,and the relationship between different preparation conditions of composite catalyst and electrochemical performance was explored.The introduction of the third transition metal Fe ion changed the electron delocalization of Co ion and Ni ion,and improved the electrocatalytic performance of MOF catalyst.Theη₁₀ of Fe（OH）₃/NiCo-MOF composite catalyst is 388 mV at 1M KOH,the Tafel slope is 45 mV·dec^-1,and the catalyst remained stable for at least 12 h.The synthesis of Fe（OH）₃ resulted in more defects on the surface of MOF,increased the conductivity of the original MOF,and accelerated the electron transfer rate of MOF.（3）NiCo-MOF/GO binary composite catalyst was prepared by solvothermal method,and Fe（OH）₃/NiCo-MOF/GO ternary composite catalyst was prepared by stirring method.The mechanism of oxygen evolution reaction catalyzed by composite catalyst was studied,and the relationship between different preparation conditions and electrochemical performance of composite catalyst was explored.The addition of GO increases the surface area of the original MOF,which provides a better platform for electron transfer in oxygen evolution reaction.Through the electrochemical performance test,η₁₀ of Fe（OH）₃/NiCo-MOF/GO in 1M KOH is370 mV,Tafel slope is 45 mV·dec^-1,and it remains stable for at least 12 h.