Preparation And Methanol Electrocatalytic Oxidation Properties Study Of Copper-based Catalyst

Direct methanol fuel cell（DMFC）has attracted much attention due to its high energy density,convenient use and low cost.The performance of DMFC largely depends on the catalyst of methanol oxidation reaction（MOR）.Currently,precious metals are commonly used as MOR catalysts.However,the scarcity of precious metals and their susceptibility to carbon monoxide poisoning restrict their wide application.Therefore,it is necessary to develop MOR catalysts based on non-noble metals.Among them,copper-based catalysts have become one of the promising catalysts for MOR due to their high activity,high abundance,good stability and low price.In this paper,simple strategies were used to prepare Cu-based nanocrystalline catalysts.That is,Cu is stabilized in a nitrogen-doped carbon（N-C）matrix by hydrothermal method,immersion method and electrodeposition method to form Cu@N-C composite material.At the same time,the prepared composite materials were characterized by XRD,Raman,SEM and TEM.Finally,through a series of electrochemical tests,the methanol electrocatalytic performance of the catalyst was evaluated.The main content and results are as follows:（1）By investigating of different synthesis factors such as polymerization temperature,time and material ratio,polyaniline polyvinyl alcohol hydrogel with ultra-high conductivity was synthesized and employed as a catalyst with the joins of crosslink reagent.And through freezing and thawing treatment,strong mechanical stress is generated inside,forming an obvious honeycomb-like structure,which has a larger specific surface area.This is more conducive to the transfer of charges to improve catalytic activity.（2）Three copper-based electrocatalysts were prepared by hydrothermal method,impregnation method and electrodeposition method,and their electrocatalytic oxidation performance of methanol was compared.The results show that the Cu/N-C（FT）@500catalyst prepared by electrodeposition has the highest electrocatalytic activity(189 m A cm^-2 at0.6 V vs SCE).In addition,after 10 h of MOR test,Cu/N-C（FT）@500 catalyst still show better stability than commercial Pt/C catalyst.In addition,through the CO poisoning test,the Cu/N-C（FT）@500 catalyst has a retention rate of 96%for the current density of MOR,which indicates that the catalyst has a good ability to resist CO poisoning.At the same time,the EIS results of the conductivity and the experimental measurement value(1.25×10⁵ S cm^-1)both confirm that the conductivity of Cu/N-C（FT）@500 is higher than that of the catalyst obtained by the other two preparation methods,which is exactly the reason why Cu/N-C（FT）@500catalyst has higher MOR activity.（3）The Cu/Co-N-C（FT）@500 electrocatalyst with core-shell structure was prepared by the best electrodeposition method.Among them,the Cu-Co alloy nanocrystals are uniformly embedded in the nitrogen-doped carbon matrix.Cu and Co act as the adsorption center of CH₃OH and the catalytic center of MOR,respectively.And the highly porous nitrogen-doped carbon matrix fixes and protects the Cu-Co alloy nanocrystals,which is also conducive to charge transfer.Under the conditions of 1 M KOH and 1 M methanol electrolyte and a voltage of 0.6 V vs.SCE,the Cu/Co-N-C（FT）@500 electrocatalyst has a higher MOR activity(301m A cm^-2).Then,after 10 h of i-t test,the catalyst can still maintain high catalytic activity.At the same time,after CO poisoning,the retention rate of Cu/Co-N-C（FT）@500 to the current density of MOR is 92%.The main reason for the excellent MOR activity and stability of the catalyst is due to the synergistic effect between Cu and Co and the porous structure of the composite material.