A template co-pyrolysis strategy towards the increase of amino/imino content within g-C3N4 for efficient CO2 photoreduction

Photocatalytic CO2 reduction reaction (CO2RR) is an effective mean to address the current environmental and energy issues. As a kind of typical photocatalyst, g-C3N4 possesses lots of advantages (i.e., facile synthesis, visible-light response, and high stability) in CO2 reduction. However, the poor capacity of CO2 capture and rapid recombination of photo-generated electron and hole, both hinder the further development of g-C3N4 for CO2RR. Herein, we developed a template co-pyrolysis strategy to prepare C–NHx-rich (x = 1 or 2) g-C3N4, to increase the CO2 binding and the subsequent photocatalytic CO2 reduction efficiency. Specifically, organic molecules with multiple imino groups were used as additives to co-pyrolyze with urea. These additives can act as templates to facilitate the formation of g-C3N4 with abundant C–NHx groups, which effectively improved the capacity of CO2 capture. Meanwhile, the capacity of light absorption and the separation of photo-generated electron and hole were also optimized. As a result, the obtained C–NHx-rich g-C3N4 showed greatly enhanced photocatalytic activity for CO2RR, over 74-fold higher than that of g-C3N4 conventionally prepared. This work provides a new avenue for optimizing the g-C3N4-based photocatalysts for CO2RR.