MOF-Transformed In 2 O 3- x @C Nanocorn Electrocatalyst for Efficient CO 2 Reduction to HCOOH

Highlights The nanocorn design enables In 2 O 3- x @C a high Faradaic efficiency of 98% and a high formate current density of 320 mA cm −2 at a low potential of -1.2 V versus hydrogen electrode without iR correction. The rich O vacancy activates In 3+ sites on the nanocube shell of In 2 O 3- x @C and the carbon cob enhances conductivity. Operando X-ray absorption spectroscopy unveils the active site of In 3+ for formate production although reduction of In 3+ to In is conceivable at the applied negative potentials during CO 2 reduction reaction.