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

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 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) achieved a high selectivity of HCOO - up to 91.4% at a low potential of -0.98 V versus reversible hydrogen electrode (vs. RHE), and a high HCOO - partial current density of 279.3 mA cm -2 at -1.1 V vs. RHE in the electrochemical flow cell. In-situ and ex-situ characterizations confirmed the PO 4 3- anions kept stable on the surface of indium during CO 2 RR, accelerating the generation of OCHO * intermediate. From density functional theory (DFT) calculations, PO 4 3- anions enriched the metal-oxygen species on the substrate to optimize the electronic structure of the catalysts and induced a local microenvironment with massive K + ions on the interface, thus reducing the activation energy barrier of CO 2 RR. This article is protected by copyright. All rights reserved.