Carbon nitride derivatives as photocatalysts for the CO2 reduction reaction: computational study

Photocatalytic reduction of CO2 to hydrocarbons is considered to be a promising strategy to solve the energy crisis and environmental problems. Herein, the electronic and optical properties, and catalytic performance of g-C3N4 derivatives [C6N7(C6H4)(1.5)](n) (systems 1 and 2), and [C6N7(C12H8)(1.5)](n) (system 3) were studied by density functional theory (DFT) computations. Compared to g-C3N4 the band gaps of systems 1-3 are smaller, and the absorption intensities of the three derivatives in the visible light region increase, indicating that these derivatives can produce more electrons under visible light irradiation and enhance the photocatalytic performance. The computational results show that the main products of CO2 reduction catalyzed by system 1 are HCOOH and CH3OH. The rate-determining step is CO2 -> COOH* with a Delta G of 1.22 eV. Therefore, system 1 is predicted to be a promising catalyst for the CO2 reduction reaction.