Study On The Synthesis Of Metal-phthalocyanine Complexes And Their Performance Of Electrocatalytic Reduction Of CO₂

Electrochemical conversion of carbon dioxide（CO₂）into hydrocarbon fuels is one of the sustainable technologies for human beings to cope with global warming and mitigate the energy crisis,which can effectively reduce the concentration of carbon dioxide in the atmosphere and produce useful industrial products.However,the problems of high overpotential and low selectivity of products still exist in the reported electrocatalysts.Based on the special two-dimensional conjugate-electronic structure,strong coordination ability,high catalytic performance and low cost of phthalocyanine,nine metal phthalocyanine complexes were synthesized.The main contents of this paper are as follows:Lead phthalocyanine（PcPb）,bismuth phthalocyanine（PcBi）,indium phthalocyanine（PcIn）were synthesized by solvothermal method,and three lead-bismuth phthalocyanine PcPb_xBi_1-x（x=0.3,0.5,0.7）and three bismuth-indium phthalocyanine PcBi_xIn_1-x（x=0.3,0.5,0.7）composites were synthesized by adjusting the molar ratio between the corresponding two metal Salts.The morphology,crystal phase,composition,and chemical valence of elements of the materials were characterized by Scanning electron microscope（SEM）,transmission electron microscope（TEM）,X-ray diffraction（XRD）,and X-ray photoelectron spectroscopy（XPS）,respectively.The performance of electrocatalytic reduction of CO₂on the synthesized materials modified electrodes in 0.5 mol·L^-1KHCO₃solution were studied by cyclic voltammetry（CV）and linear sweep voltammetry（LSV）.The results showed that all the nine materials can electrocatalyze the electro-reduction of CO₂,and the bimetallic phthalocyanine composites have better electrocatalytic performance than the single metallic phthalocyanine.The Faraday efficiency of formate ion(FE^-_HCOO)was obtained by i-t curves and ion chromatography.Among them,FE^-_HCOOof PcPb_0.3Bi_0.7was as high as 82.3%at low the potential of-0.9V（vs RHE）,showing high selectivity of products.FE^-_HCOOof the bimetallic bismuth-indium phthalocyanine are all over 70%in a wide potential range of-0.9～-1.2V（vs RHE）,and PcBi_0.7In_0.3has the highest current density and the best catalytic performance with FE^-_HCOOmore than95%.The results further reveal PcBi_0.7In_0.3and PcBi_0.7In_0.3have good catalytic activity due to good electrical conductivity and the larger electroactive specific surface area and the synergistic catalysis of bismuth phthalocyanine and lead phthalocyanine（or indium phthalocyanine）.Furthermore,the mechanism of electrocatalytic reduction of CO₂by metalic phthalocyanine has been deduced by Tafel slope.In this paper,we provide a new idea and method for designing efficient composite electrocatalyst for CO₂reduction by adjusting the molar ratio of metals.