Synthesis and Characterization of Cu based ZIF-8 catalysts for Electro-catalytic CO2 Reduction /

Abstract

Electrochemical reduction of carbon dioxide is a valuable process in which CO2 is converted to beneficial chemicals, hydrocarbons, and fuels. Numerous catalysts have experimented earlier for the CO2 reduction process but the challenge for gaining good stability, selectivity, and activity of required product remains. Varying Cu2+ doping catalysts of Cu-doped ZIF-8 have been synthesized by the solvothermal process and characterized in this work. The characterization techniques used were XRD, SEM, EDS, TGA, BET, and FTIR to find the physicochemical properties of our material. The Cu/ZIF-8 catalysts characterization was compared with a reference material of ZIF-8, which helped in identifying changes to the material morphology, thermal stability, surface area, porosity, and adsorption ability of ZIF-8 as copper is doped in it. The final catalyst samples were then tested on the electrochemical workstation for their current density activity in electrochemical CO2 reduction. Constant potential electrolysis was performed at specified constant potentials within a voltage range and gas samples were collected after each experiment for their analysis through gas chromatography. With respect to earlier study on copper materials the Cu30%ZIF-8 exhibited a greater current density of -40 mA cm-2 at -2.1 V vs. Ag/AgCl and even enhanced selectivity for methane. While Cu10%-ZIF8 showed the highest selectivity for carbon monoxide with a faradaic efficiency of 62.26% at -1.5 V vs. Ag/AgCl. The sufficient copper active metal sites of our catalyst, dual-porosity nature of structure along with the broad surface area of zeolite and high N-content helped in achieving high activity and performance of our crystalline Cu/ZIF-8 catalyst for carbon dioxide electroreduction.