Study On The Preparation Of ZIFs Composite Material And The Performance Of Oxygen Evolution By Electrolytic Water

Global sustainable development and clean energy have become a major issue,and hydrogen as a recyclable,pollution-free and high energy density clean energy has also attracted attention.Among hydrogen production technologies,electrolysis water technology is considered the most potential and efficient hydrogen production method.However,to achieve efficient hydrogen production,the rate of anodic oxygen evolution reaction（OER）is the most important constraint.Precious metal-based catalysts（IrO₂ and RuO₂）are used as benchmark electrocatalysts for OER,but due to the lack of resources and high prices of these materials,they have become a bottleneck restricting their industrialization.Therefore,the development of low-cost and efficient OER electrocatalysts has become a new development direction.Zeolite imidazole metal-organic frameworks（ZIFs）are a new type of oxygen evolution reaction catalyst with excellent properties such as high porosity,multifunctional surface,and high specific surface area.However,ZIFs have the defect of low conductivity,which limits their potential for widespread application in the field of electrolytic water oxygen evolution.Therefore,people expect to improve the conductivity of ZIFs through methods such as composite or doping with conductive materials.Based on this,this paper will composite bimetallic organic frameworks（ZIFs）with conductive materials(MWCNTs or（NH₄）₃PMo₁₂O₄₀)to study the OER electrocatalytic performance of the composite materials.The specific research content is as follows:（1）Zn_xCo_y-ZIFs with different Zn/Co ratios were synthesized by in-situ growth method.The LSV polarization curve showed that when the Zn/Co ratio was 1:3,the Zn₁Co₃-ZIFs sample had the smallest overpotential of 315.2 mV.Composite Zn₁Co₃-ZIFs with different amounts of carbon nanotubes（MWCNTs）.The 25%MWCNTs/Zn₁Co₃-ZIFs composite material exhibits the most excellent OER electrocatalytic performance in a 1 M KOH electrolyte solution,with a over potential of 215.2 mV at a current density of 10mA/cm².After stability testing of 25%MWCNTs/Zn₁Co₃-ZIFs composite material at a potential of 1.43 V for 30 hours,the potential stabilized.The addition of MWCNTs not only improves the conductivity of Zn₁Co₃-ZIFs,but also effectively improves their dispersion,thus providing more active site,making the composite have excellent OER electrocatalytic performance.25%MWCNTs/Zn₁Co₃-ZIFs composites show excellent OER performance,but excessive MWCNTs will reduce Co and Zn active site in the composites,inhibit the catalytic activity of OER,and reduce the electrochemical active surface area.Therefore,25%MWCNTs/Zn₁Co₃-ZIFs composites have excellent OER performance.（2）ZnCo-ZIFs were compounded with（NH₄）₃PMo₁₂O₄₀ to synthesize（X）NPMO@Zn₁Co₃-ZIFs compound material.Zn₁Co₃-ZIFs bimetallic organic framework coated（NH₄）₃PMo₁₂O₄₀ material was synthesized through in-situ assembly of the main body,and（X）NPMO@Zn₁Co₃-ZIFs compound material.The effect of different concentrations of NPMO on the electrochemical performance of composite materials was studied.10%NPMO@Zn₁Co₃-ZIFs composite material has the best OER performance,with an overpotential of 213.2 mV at a current density of 10 mA/cm²,which is 102 mV lower than Zn₁Co₃-ZIFs.10%NPMO@Zn₁Co₃-ZIFs composite material has been tested for stability at a high potential of 1.48 V for 24 hours and exhibits good stability.The addition of high conductivity NPMO can improve the electron transfer ability of Zn₁Co₃-ZIFs,resulting in an improvement in the OER performance of Zn₁Co₃-ZIFs.10%NPMO@Zn₁Co₃-ZIFs composite shows excellent OER performance,which is because it have the largest electrochemical active surface area and can expose more active site.However,as the amount of NPMO composite increases and it carries strong negative charges,it can provide many nucleation sites during the reaction process,thereby promoting the aggregation of Zn₁Co₃-ZIFs.Therefore,10%NPMO@Zn₁Co₃-ZIFs composites have excellent OER performance.（3）Co_xNi_y-ZIFs with different Co/Ni ratios were synthesized by in-situ growth method.LSV testing showed that when the Co/Ni ratio was 1:3,Co₃Ni₁-ZIFs had the lowest overpotential of 313.2 mV.Co₃Ni₁-ZIFs were coated with different contents of NPMO by in-situ assembly of the main body to obtain（X）NPMO@Co₃Ni₁-ZIFs compound material.The 15%NPMO@Co₃Ni₁-ZIFs composite material exhibits the most excellent OER electrocatalytic performance in a 1 M KOH electrolyte solution,with a over potential of 244.2 mV at a current density of 20 mA/cm²,which is 68 mV lower than pure phase Co₃Ni₁-ZIFs.15%NPMO@Co₃Ni₁-ZIFs after stability testing of the composite material at a potential of 1.40 V for 26 hours,the potential remained basically unchanged.The addition of high conductivity NPMO can improve the electron transfer ability of Co₃Ni₁-ZIFs,resulting in an improvement in the OER performance of Co₃Ni₁-ZIFs,which is more conducive to the OER reaction of Co₃Ni₁-ZIFs.15%NPMO@Co₃Ni₁-ZIFs composite shows excellent OER performance,which is because it has the largest electrochemical active surface area and can expose more active site.However,as the amount of NPMO composite increases and it carries strong negative charges,it can provide many nucleation sites during the reaction process,thereby promoting the aggregation of Co₃Ni₁-ZIFs.Therefore,15%NPMO@Co₃Ni₁-ZIFs composites have excellent OER performance.