Engineering the CuO–HfO2 interface toward enhanced CO2 electroreduction to C2H4

We report significantly enhanced electrochemical CO2 reduction (ECR) to C2H4 by tuning the interface of a metal oxide composite (CuOx/HfO2), enabling a C2H4 faradaic efficiency as high as 62.6 ± 1.3% at 300 mA cm−2, in contrast to only 11.6 ± 1.6% over pure CuO. Collective knowledge from multiple control experiments, density functional theory calculations, and operando Raman study reveals that the CuOx–HfO2 interface greatly strengthens CO2 adsorption and the binding of *CO for further C–C coupling to yield C2H4.