Constructing C–O bridged CeO2/g-C3N4 S-scheme heterojunction for methyl orange photodegradation：Experimental and theoretical calculation

Owing to its feasibility, efficiency in light-harvesting and effectiveness in the interfacial charge transfer between two n-type semiconductors, constructing heterojunction photocatalysts have been identified as an effective way for enhancing the photocatalytic properties. In this research, a C–O bridged CeO2/g-C3N4 (cCN) Step-scheme (S-scheme) heterojunction photocatalyst was constructed successfully. Under visible light irradiation, the cCN heterojunction exhibited the photocatalytic degradation efficiency of methyl orange, which was about 4.5 and 1.5 times higher than that of pristine CeO2 and CN, respectively. The DFT calculations, XPS and FTIR analyses demonstrated the formation of C–O linkages. And the calculations of work functions revealed the electrons would flow from g-C3N4 to CeO2 due to the difference in Fermi levels, resulting in the production of internal electric fields. Benefiting from the C–O bond and internal electric field, the photo-induced holes in the valence band of g-C3N4 and the photo-induced electrons from conduction band of CeO2 would be recombined when exposed to visible light irradiation, while leaving the electrons with higher redox potential in the conduction band of g-C3N4. This collaboration accelerated the separation and transfer rate of photo-generated electron-hole pairs, which promoted the generation of superoxide radical (•O2−) and improved the photocatalytic activity.