g-C3N4/BiOI S-scheme heterojunction: A 2D/2D model platform for visible-light-driven photocatalytic CO2 reduction and pollutant degradation

Photo-degradation of pollutant and photo-reduction of CO2 are efficient ways to address challenges of water pollution, the greenhouse effect and energy crisis, respectively. In our work, via fastening two-dimensional (2D) BiOI nanoplates on 2D g-C3N4 nanosheets, a BiOI/g-C3N4 (BI/CN) S-scheme photocatalyst with closely stacked structure were prepared though a self-assembly process. The prepared BI/CN S-scheme heterojunction could improve the transfer and separation efficiency of photo-generated electron-hole pairs by facilitating the electrons transfer from BiOI to g-C3N4. Under visible light exposure, the photo-degradation efficiencies of tetracycline hydrochloride (TC) and p-chlorophenol (4-PC) by BI/CN-50% reached nearly 100% and 46%, respectively, which were more excellent in comparison with other samples. And BI/CN-50% sample exhibited the best CO production (12.45 mu mol.g(-1)) with visible-light irradiation of 4 h. This value was approximately 4.37 and 5.41 times higher than that of BI (2.85 mu mol.g(-1)) and CN materials (2.30 mu mol.g(-1)), respectively. Moreover, the excellent photocatalytic performance had no visible decay during five cycles. Meanwhile, an S-scheme charge transfer process was confirmed by species trapping experiments and electron spin-trap analysis. This study offers new insights into the activity, kinetics, and mechanism over BiOI-based materials for photocatalysis technology.