The green and clean sunlight-driven catalytic conversion of CO2 into high-value-added chemicals can simultaneously solve the greenhouse effect and energy problems. The controllable preparation of semiconductor catalyst materials and the study of refined structures are of great significance for the in-depth understanding of solar-energy-conversion technology. In this study, we prepared nitrogen-doped NiO semiconductors using a one-pot molten-salt method. The research shows that the molten-salt system made NiO change from p-type to n-type. In addition, nitrogen doping enhanced the adsorption of CO2 on NiO and increased the separation of photogenerated carriers on the NiO. It synergistically optimized the CO2-reduction system and achieved highly active and selective CO2 photoreduction. The CO yield on the optimal nitrogen-doped photocatalyst was 235 μmol·g-1·h-1 (selectivity 98%), which was 16.8 times that of the p-type NiO and 2.4 times that of the n-type NiO. This can be attributed to the fact that the nitrogen doping enhanced the oxygen vacancies of the NiOs and their ability to adsorb and activate CO2 molecules. Photoelectrochemical characterization also confirmed that the nitrogen-doped NiO had excellent electron -transfer and separation properties. This study provides a reference for improving NiO-based semiconductors for photocatalytic CO2 reduction.
Keywords: NiO; nitrogen doping; photocatalysis; reduction of CO2.