Direct Z-scheme photocatalytic CO2 conversion to solar fuels in a two-dimensional C2N/aza-CMP heterostructure

Abstract Photocatalytic CO2 conversion to reproducible hydrocarbon fuels, as a promising approach to solve the present environment and energy problems, has drawn increasing attention. The activity and selectivity of the photocatalytic CO2 reduction reactions (CO2RR) are crucial for improving the CO2 conversion efficiency. Here, we propose a two-dimensional (2D) Van der Waals (VDW) heterostructure as a potential direct Z-scheme photocatalytic system to achieve this goal. The VDW heterostructure is composed of a C2N monolayer and a 2D polymeric aza-CMP monolayer, both of which have been synthesized. Our first-principles calculations show that the C2N/aza-CMP hetero-bilayer (HBL) has the spatially separated photogenerated carriers, along with potent visible-light absorption and robust redox ability, which facilitate highly-efficient photocatalytic CO2RR. More importantly, the Cu-dimer anchored on the C2N monolayer not only effectively lowers the overpotential of CO2RR to the level that can be offered by photogenerated carriers, but also achieves high selectivity towards photocatalytic production of CH4 from CO2. This study ushers in a new avenue for improving the solar-to-fuel energy conversion efficiency.