Z-scheme junction Bi2O2(NO3)(OH)/g-C3N4 for promoting CO2 photoreduction

•Bi2O2(NO3)(OH)/g-C3N4 was prepared by electrostatic self-assembly method.•It shows enormously promoted photocatalytic activity for CO2 reduction.•The Z-scheme junction was formed in the Bi2O2(NO3)(OH)/g-C3N4 composite.•Z-scheme junction favors the charge separation of Bi2O2(NO3)(OH)/g-C3N4. Photocatalytic CO2 reduction is believed to be an emerging strategy to address fossil fuels consumption and global warming problems. However, the rapid recombination of photogenerated carriers restricts the application of photocatalytic technology severely. Constructing heterojunction structure is one of the most effective pathways to facilitate the charge separation and photocatalytic performance. In this work, a series of direct Z-scheme heterojunction Bi2O2(NO3)(OH)/g-C3N4 (BON/CN) was developed by an electrostatic self-assembly method. The optimal BON/CN-2 photocatalyst exhibits a conspicuous photocatalytic CO2 reduction activity with a high CO evolution rate of 14.84 µmol g-1h−1 under the stimulated solar light irradiation, which is about 15 and 3.5 times higher than that of pure BON and g-C3N4, respectively. The significantly promoted photocatalytic performance is attributed to the tightly-contact interface and formation of Z-scheme between BON and g-C3N4, which favor for the separation and transfer of photogenerated electrons and holes, as confirmed by high resolution transmission electron microscope (HRTEM), electron spin resonance (ESR), photoelectrochemical measurement and photoluminescence (PL) results. This work may provide a new reference for developing rational tactics to fabricate efficient Z-scheme heterojunction photocatalysts for CO2 conversion.