Unlocking the Potential of Bi2S3‐Derived Bi Nanoplates: Enhanced Catalytic Activity and Selectivity in Electrochemical and Photoelectrochemical CO2 Reduction to Formate

Abstract Various electrocatalysts are extensively examined for their ability to selectively produce desired products by electrochemical CO 2 reduction reaction (CO 2 RR). However, an efficient CO 2 RR electrocatalyst doesn't ensure an effective co‐catalyst on the semiconductor surface for photoelectrochemical CO 2 RR. Herein, Bi 2 S 3 nanorods are synthesized and electrochemically reduced to Bi nanoplates that adhere to the substrates for application in the electrochemical and photoelectrochemical CO 2 RR. Compared with commercial‐Bi, the Bi 2 S 3 ‐derived Bi (S‐Bi) nanoplates on carbon paper exhibit superior electrocatalytic activity and selectivity for formate (HCOO − ) in the electrochemical CO 2 RR, achieving a Faradaic efficiency exceeding 93%, with minimal H 2 production over a wide potential range. This highly selective S‐Bi catalyst is being employed on the Si photocathode to investigate the behavior of electrocatalysts during photoelectrochemical CO 2 RR. The strong adhesion of the S‐Bi nanoplates to the Si nanowire substrate and their unique catalytic properties afford exceptional activity and selectivity for HCOO − under simulated solar irradiation. The selectivity observed in electrochemical CO 2 RR using the S‐Bi catalyst correlates with that seen in the photoelectrochemical CO 2 RR system. Combined pulsed potential methods and theoretical analyses reveal stabilization of the OCHO* intermediate on the S‐Bi catalyst under specific conditions, which is critical for developing efficient catalysts for CO 2 ‐to‐HCOO − conversion.