Photocatalytic conversion of carbon dioxide on triethanolamine: Unheeded catalytic performance of sacrificial agent

Potential catalytic performance of sacrificial agents triethanolamine (TEOA) has not been explored yet, seriously affecting the evaluation of catalyst performance and reaction mechanism. Herein, we report direct evidence of TEOA, a popular sacrificial agent in CO2 photoreduction, photocatalytic conversion of CO2 into CO and CH4 for the first time. Combining experimental and theoretical studies, it is corroborated that TEOA with terminal hydroxyl group as active site serves as a photocatalyst possessing appropriate energy level for the ultraviolet light response. Comprehensive investigations endorsed that the two products of CH4 and CO are derived from conventional photocatalytic CO2 hydrogenation and photoinduced homocleavage of RO-COOH followed by a hydrogen atom transfer process, respectively. The current work demonstrates the nonnegligible catalytic influence of TEOA and provides guidance in choosing suitable sacrificial agents during solid–liquid photocatalytic redox reactions.