Enriching Metal–Oxygen Species and Phosphate Modulating of Active Sites for Robust Electrocatalytical CO 2 Reduction

Abstract Direct electrochemical reduction of CO 2 (CO 2 RR) into value‐added chemicals is a promising solution to reduce carbon emissions. The activity of CO 2 RR is influenced deeply by the reaction microenvironment and electronic properties of the catalysts. Herein, the surface PO 4 3− anions are tuned to modulate the local microenvironment and the electronic properties of the indium‐based catalyst with abundant metal–oxygen species enabling efficient electrochemical conversion of CO 2 to HCOO − . Indium nanoparticles coupled with PO 4 3− anions (PO 4 3− ‐In NPs) achieve a high selectivity of HCOO − up to 91.4% at a low potential of −0.98 V versus reversible hydrogen electrode (versus RHE) and a high HCOO − partial current density of 279.3 mA cm −2 at −1.1 V versus RHE in the electrochemical flow cell. In situ and ex situ characterizations confirm the PO 4 3− anions keep stable on the surface of indium during CO 2 RR, accelerating the generation of OCHO * intermediate. From density functional theory calculations, PO 4 3− anions enrich the metal–oxygen species on the substrate to optimize the electronic structure of the catalysts and induce a local microenvironment with massive K + ions on the interface, thus reducing the activation energy barrier of CO 2 RR.