4‐Mercaptophenylboronic Acid‐Grafted CuO Simultaneously Enhances *CO Adsorption and *H Supply to Boost the Electroreduction of CO ₂ to C ₂₊ Products

ABSTRACT A molecular modification strategy is effective for enhancing the selectivity of copper (Cu)‐based catalysts to multi‐carbon (C 2+ ) products in the electrochemical CO 2 reduction reaction (eCO 2 RR). However, conventional modifying molecules fail to simultaneously optimize *CO adsorption and *H supply on the catalysts, greatly limiting efficient formation of C 2+ products. Herein, a novel modification strategy using a bifunctional 4‐mercaptophenylboronic acid (MPBA) molecule is reported to simultaneously enhance *CO adsorption and *H supply on Cu‐based catalysts. The optimal CuO‐MPBA‐0.4 catalyst achieved a Faradaic efficiency of 86.4% for C 2+ products with a partial current density of 751.5 mA·cm −2 , exceeding those of most molecularly modified Cu‐based catalysts reported. Mechanistic investigations and theoretical calculations demonstrated that the mercaptan groups in MPBA molecules formed Cu–S bonds with Cu, increasing the d ‐band center of Cu sites, which enhanced *CO adsorption on CuO‐MPBA‐0.4. Concurrently, the phenylboronic acid groups in MPBA molecules accelerated H 2 O dissociation, ensuring a sufficient *H supply in the eCO 2 RR, and thus promoting the hydrogenation of *CO to *CHO as well as asymmetric *CO–*CHO coupling. This unique synergistic mechanism of simultaneously enhancing *CO adsorption and *H supply provides new insights for other electrocatalytic reaction systems involving intermediate activation and *H transfer.