Engineering the CuO-HfO 2 interface toward enhanced CO 2 electroreduction to C 2 H 4 .

We report significantly enhanced electrochemical CO 2 reduction (ECR) to C 2 H 4 by tuning the interface of a metal oxide composite (CuO x /HfO 2 ), enabling a C 2 H 4 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 CuO x -HfO 2 interface greatly strengthens CO 2 adsorption and the binding of *CO for further C-C coupling to yield C 2 H 4 .