Study Of Metal Macrocycle Compound For Electrochemical CO₂ Reduction

Excessive CO₂ emissions from fossil fuel combustion pose a potential threat to the global climate.Electrochemical CO₂ conversion is likely to store renewable energy or surplus nuclear energy while reducing the concentration of CO₂ in the atmosphere,showing a certain application prospect.However,electrochemical CO₂ conversion faces challenges due to the lack of electrocatalysts with low overpotential,high selectivity and good durability.In this paper,electrochemical CO₂ conversion was studied from the metal macrocyclic compound electrocatalyst materials and reaction system.The main results are as follows:?1?A positively charged protonated Co?III?meso-tetra?4-pyridyl?porphyrin?CoTPyP?and a negatively charged Co?III?meso-tetra?4-sulfonatophenyl?porphyrin?CoTPPS₄?were prepared by ionic self-assembly method.The carbon black is added and ultrasonically dispersed,so that the Co porphyrin nanoaggregates are dispersed on the surface of the carbon support.After mild pyrolysis at 350°C,the Co porphyrin molecule loses only the axial ligand Cl and some peripheral groups and is closely adsorbed onto the carbon support.The prepared electrocatalyst has a Faradaic efficiency of 88±1.5%for CO₂ conversion to CO and a current density of 8 mA cm^-2 at an overpotential of 430 mV(E^o_CO2/CO=-0.11 V vs.RHE).In addition,under 20 h of potentiostatic electrolysis,the Faradaic efficiency of CO was maintained above85%,and the current density was only attenuated by 7%.In this paper,electrochemical CO₂reduction uses a low-temperature liquid phase reduction system,and the closed H-type electrolytic cell is a reactor.At the same time,the electrolytic cell and gas chromatography were combined to realize the on-line detection of gas products.?2?By ionic self-assembly method,the positively charged Alcian blue pyridine variant?CuPc?and the negatively charged Cu?III?meso-tetra?4-sulfonatophenyl?porphyrin?CuTPPS₄?are assembled into nanostructured materials by electrostatic interaction in an aqueous environment.After the addition of carbon black,the self-assembled nanostructures were supported on a carbon support by ultrasonication,and two electrocatalyst materials were obtained by heat treatment at different temperatures:a carbon-supported Cu-N₄ electrocatalyst was obtained by mild pyrolysis at 300°C and a nitrogen-doped carbon-supported Cu₂O electrocatalyst was obtained by heat treatment at 800°C.The carbon-supported Cu-N₄ catalyst material prepared in this chapter has a 14%CO Faradaic efficiency and a current density of 1.97mA cm^-2 at-0.55 V vs.RHE.The nitrogen-doped carbon-supported Cu₂O electrocatalyst has a CO Faradaic efficiency of 65.7%and a small amount of CH₄ product at-0.65 V vs.RHE,corresponding to a current density of 5.38 mA cm^-2.