BiOI/Co ₉ S ₈ Heterojunction Electrocatalyst for CO ₂ ‐to‐Methanol Conversion via Formate‐Mediated Pathway

ABSTRACT Electrochemical CO 2 reduction (CO 2 RR) to methanol offers a sustainable route for greenhouse gas mitigation and renewable energy storage, yet suffers from low selectivity due to competing pathways and intermediate instability. Herein, a BiOI/Co 9 S 8 heterojunction electrocatalyst was constructed, leveraging its unique nanotube architecture and the synergistic effect of the heterojunction to achieve highly efficient and selective CO 2 ‐to‐methanol conversion. In an H‐type cell, the catalyst exhibited a Faradaic efficiency of 68.29% for methanol at −0.9 V versus RHE and sustained stable operation for 60 h. In a flow cell, the methanol production rate reached 817.48 µmol h −1 cm −2 , with a partial current density of 122.57 mA cm −2 . Comparative experiments and calculations confirm that the synergistic interaction and interfacial confinement between BiOI and Co 9 S 8 lowers the energy barrier for the key intermediate HCOOH*, suppresses the formation of key intermediates such as *OCHO and *CO along the CO pathway, and thereby enables methanol production via the HCOOH pathway. This synergistic mechanism offers a novel strategy for the design of high‐performance CO 2 electroreduction catalysts for methanol synthesis.