Enriching Metal–Oxygen Species and Phosphate Modulating of Active Sites for Robust Electrocatalytical CO2 Reduction

Direct electrochemical reduction of CO₂ (CO₂ RR) into value-added chemicals is a promising solution to reduce carbon emissions. The activity of CO₂ RR is influenced deeply by the reaction microenvironment and electronic properties of the catalysts. Herein, the surface PO₄ ^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 CO₂ to HCOO^- . Indium nanoparticles coupled with PO₄ ^3- anions (PO₄ ^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 PO₄ ^3- anions keep stable on the surface of indium during CO₂ RR, accelerating the generation of OCHO^* intermediate. From density functional theory calculations, PO₄ ^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 CO₂ RR.