Insight into photocatalytic CO reduction on TiO-supported Cu nanorods: a DFT study on the reaction mechanism and selectivity.

Photoreduction of CO into hydrocarbons is a potential strategy for reducing atmospheric CO and effectively utilizing carbon resources. Cu-deposited TiO photocatalysts stand out in this area due to their good photocatalytic activity and potential methanol selectivity. However, the underlying mechanism and factors controlling product selectivity remain less understood. Using first-principles calculations, this study systematically investigates the possible reaction network for CO photocatalytic reduction on TiO supported Cu-nanorods (nr-Cu/TiO), driven by the surface-bound *H species generated a Volmer-like process (H + e + * → *H). Our results reveal that the initial hydrogenation of CO on nr-Cu/TiO is energetically more favorable the formate (HCOO) pathway than the carboxyl (COOH) route. Notably, HCOO undergoes further hydrogenation for effective C-O bond cleavage, with HCOOH identified as the key intermediate. Both CO (CO → HCOO → HCOOH → HCO → CO) and CHOH (CO → HCOO → HCOOH → HCO → CHOH) production share the HCO intermediate, with CO formation proceeding an unexpected "forth-back" mechanism. Energy profiles suggest that CHOH formation is more favorable than CO formation. Additionally, excess photogenerated electrons were found to enhance CO activation and C-O bond cleavage to some extent but have minimal impact on other reaction steps. This study provides atomic-level insights into the CO photoreduction mechanism, offering potential guidance for improving product selectivity.