Rapid flame synthesis of carbon doped defective ZnO for electrocatalytic CO2 reduction to syngas

Abstract

A strategy was established to develop a promising catalyst for electrochemical CO2 reduction to syngas. The ZnO doped carbon with oxygen vacancies was successfully prepared by rapid flame synthesis. Through manipulation of fabrication parameters, carbon compositions and oxygen vacancies in the catalysts were controllable. How the different contents of carbon doped in the catalyst effected on the electrocatalytic activities were investigated. Density functional theory (DFT) calculations reveal that carbon doping reduce the carbon monoxide desorption energy in rate-limiting step, which contributes to CO2 conversion to CO. The synergistic effect of carbon doping and oxygen vacancy in the catalyst transform the rate-determining step of the overall reaction and decrease the change in free energy for the formation of CO and H2, which facilitates the control of CO/H2 ratio in the syngas. The ZnO rich in carbon doping and oxygen vacancies exhibits large current density for CO2 electrochemical reduction of 27.07 mA/cm2 at -1.2 V vs. RHE, where the maximum FE for CO production is 71%. The range of CO/H2 ratio is adjustable and the maximum range is from 0.67 to 2.7, which is applicable for the further conversion of target fuels and chemicals. The carbon doped defective ZnO prepared by flame synthesis provides a new option for catalyst design.