Evidence on C–C Coupling to Acetate as Key Reaction Intermediate in Photocatalytic Reduction of CO₂ over Pt/TiO₂

Abstract

Photocatalytic conversion of CO 2 with H 2 O is an attractive application that has the potential to mitigate environmental and energy challenges through the conversion of CO 2 to hydrocarbon products such as methane. However, the underlying reaction mechanisms remain poorly understood, limiting real progress in this field. In this work, a mechanistic investigation of the CO 2 photocatalytic reduction on Pt/TiO 2 is carried out using an operando FTIR approach, combined with chemometric data processing and isotope exchange of ( 12 CO 2 + H 2 O) toward ( 13 CO 2 + H 2 O). Multivariate curve resolution analysis applied to operando spectra across numerous cycles of photoactivation and the CO 2 reaction facilitates the identification of principal chemical species involved in the reaction pathways. Moreover, specific probe-moleculeassisted reactions, including CO and CH 3 COOH, elucidate the capacity of selected molecules to undergo methane production under irradiation conditions. Finally, isotopic exchange reveals conclusive evidence regarding the nature of the identified species during CO 2 conversion and points to the significant role of acetates resulting from the C−C coupling reaction as key intermediates in methane production from the CO 2 photocatalytic reduction reaction.