The fabrication of two-dimensional g-C3N4/NaBiO3·2H2O heterojunction for improved photocatalytic CO2 reduction: DFT study and mechanism unveiling.

Abstract Photocatalytic CO2 reduction is typically limited by the separation efficiency of photogenerated carriers for a single semiconductor. Thus, fabricating a two-dimensional/two-dimensional (2D/2D) heterojunction photocatalyst with high separation efficiency of photogenerated carriers has become a research priority. Here, a 2D/2D g-C3N4/NaBiO3·2H2O (CN/NBO) heterojunction photocatalyst was successfully synthesized for CO2 photoreduction. With the assistance of the nature of CN, the 10CN/NBO composite showed the best performance with the production yield rates of 110.2 and 43.8 µmol g−1 for CO and CH4, respectively. Our experiments showed that the introduction of CN in CN/NBO composites, which is under the step-scheme (S-step) transfer direction of photogenerated carriers, could greatly inhibit the recombination of photogenerated e−-h+ pairs to prolong the carriers' lifetime, which was further confirmed by analysis of photoluminescence and photochemical characterization. As we expected, the CN/NBO composites show improved photocatalytic CO2 reduction activity. The in situ infrared spectroscopy was also performed to study the intermediate products of the photocatalytic CO2 reduction process. This study provides a way to design CN-based heterojunction photocatalysts for CO2 photoreduction.