High-selectivity electrochemical conversion of CO2 to lower alcohols using a multi-active sites catalyst of transition-metal oxides

Abstract

In this paper, Ag-Co3O4-CeO2/LGC with multi-active sites was prepared by introducing transition metals and their oxides (Ag, Co & Ce) on the surface of low graphitized carbon (LGC) to control the electronic structure of the catalyst surface, which has more positive onset potential (−0.36 V vs. RHE) for CO2ER, and highly Faraday efficiency of 77.6% for lower alcohols at −0.85 V (vs. RHE) (methanol = 23.4%, ethanol = 54.2%). Its excellent catalytic performance could be attributed to the fact that Ce4+ was reduced to Ce3+ by Co2+ ions with the presence of Ag in Ag-Co3O4-CeO2/LGC, which facilitated the removal of lattice oxygen of the CeO2 surface to form high concentration oxygen vacancy. Due to the presence of high concentration oxygen vacancy, the surface electronic states of Ag-Co3O4-CeO2/LGC were refactored, providing appropriate electron energy state for facilitating *CO2δ− formation on Ce atom surface with the oxygen vacancy to decrease the CO2ER overpotential. More important, the addition of Ag atoms also enhance the adsorption for CO and a moderate adsorption for H+ to form a “*CO pool” (carbonyl cell), which was favorable for the CC coupling reaction to improve the selectivity of ethanol.