In-situ traced intermediate dynamics and reaction mechanisms in heterogenous CO2 photoreduction systems

The demonstration of in-situ traced intermediate dynamics and reaction mechanisms in the heterogenous photocatalytic CO 2 reduction process, a profound and in-depth understanding of stepping towards carbon neutrality. The in-situ tracking of redox intermediates during the photocatalytic CO 2 reduction process (PCRP) is pivotal in producing valued chemical energy. However, the co-existence and uncontrollability of these intermediates make elucidating the PCRP reaction mechanism extremely challenging. This review assesses the interplay between PCRP-derived intermediates and targeted active sites to achieve desired products via discrete reaction routes involving sequential proton-coupled electron transfers. More specifically, intermediates dynamics including adsorption, transition, stabilization, C C coupling, and desorption are analyzed and thus clarified for producing CO, CH 4 , HCOOH, HCHO, CH 3 OH, CH 3 COOH, CH 3 CHO, CH 3 CH 2 OH, C 2 H 4 , C 2 H 6 , and C 3 H 8 , thereby offering a unique aspect for optimizing PCRP. Our review begins by highlighting the PCRP phenomenon, heterogeneous reactor setup, PCRP-derived products, and their reaction routes. Furthermore, it showcases in-situ challenges, proposes feasible solutions, furnishes notable considerations for upgrading PCRP to the industrial level and provides an outlook for robust PCRP. This work may offer directions for realizing sustainable energy and the environment through an in-depth understanding of PCRP intermediate dynamics and reaction mechanisms.