Dr Ziyun Wang, University of Auckland
Rational Catalyst Design for CO2 Electrochemical Reduction Reaction
Selectivity is very important in electrochemical reduction of CO2(CO2RR) both scientifically and industrially. Recently, C2 selectivity has exceeded 80% on Cu-based catalyst using the flow cell, and ethylene and ethanol are the main two products. Understanding the mechanism branching the ethylene and ethanol is the key to achieve high selectivity of CO2RR. In this work, we first used density functional theory (DFT) calculations to understand the reaction pathways of CO2RR to ethylene and ethanol. The reaction barriers and enthalpy changes are calculated for the elementary steps considered in the two pathways on Cu(100). Based on the DFT results, we investigated two factors that could affect the ratio between ethylene and ethanol, namely CO coverage and surface decoration. Using DFT calculation, we found that CO coverage could affect the relative energies of intermediates along ethylene and ethanol pathways, thus favoring one product over the other. With the decrease of CO coverage, the ethylene pathway becomes more favorable. Experiment results suggest the same trend and the highest ethylene selectivity is achieved with low CO partial pressure in CORR experiment. We also investigated the effect of surface decoration and found metal oxide and surface condiment favors ethanol.
