Oxygen vacancy-rich Ni2P2O7 modified g-C3N4 heterojunction for highly-efficient CO2 photoreduction

Oxygen vacancy-rich Ni2P2O7/g-C3N4 heterojunction with high photogenerated carrier supply and excellent CO2 adsorption ability was prepared for efficient CO2 photoreduction. The yields of CO and CH4 with Ni2P2O7/g-C3N4 (3-NC) as the catalyst were about 53.85 and 14.28 μmol·g−1·h−1, which were 5 and 16 times greater than that of g-C3N4 under the UV–Vis irradiation. Experiments and DFT calculations revealed the modification of g-C3N4 with Ni2P2O7 can significantly accelerate the photogenerated electrons’ transfer from g-C3N4 to Ni2P2O7 through the built-in electric field. CO2-adsorption test and CO2-adsorption energy displayed Ni2P2O7 can effectively act as the CO2 capture unit to increase the reaction probability of electrons and CO2, thereby enhancing the CO2 photoreduction performance. 13CO2 isotope experiment, in-situ FTIR, in-situ XPS and Gibbs free-energy calculations were applied to explore the CO2 photoreduction process. Finally, a potential CO2 photoreduction mechanism with synergistic enhancement of oxygen vacancy and the built-in electric field was proposed.