Construction of S-scheme heterojunction for enhanced photocatalytic conversation of NO over dual-defect CeO2−x/g-C3N4−x

An increasing amount of nitric oxide (NOx) is being discharged into the atmosphere due to the development of industry and combustion of fossil fuels. Photocatalysis, as a green and renewable technology, has attracted increasing attention from global researchers to address environmental pollution caused by excessive NOx in air. g-C3N4 is a metal-free organic polymer photocatalyst that has received widespread attention due to its unique physical and chemical properties. However, the photocatalytic activity of g-C3N4 under visible light irradiation is limited by high photocarrier recombination, poor conductivity, and low visible light utilization. The construction of novel S-scheme heterojunction semiconductors based on g-C3N4 is a promising strategy to enhance the photocatalytic activity. In this study, S-scheme CeO2−x/g-C3N4−x (Ce/CN) photocatalysts were synthesized by the thermal polymerization of melamine and Ce(NO3)4. The photocatalytic activity of the as-prepared photocatalysts was investigated for the removal of NO with visible-light irradiation. The photocatalytic efficiency of 4Ce/CN was about 1.7 times higher than that of g-C3N4 with a low NO2 yield. Material characterization and DFT analysis demonstrated that the enhanced photocatalytic activity was attributed to N and O dual defects, the excellent conductivity of CeO2, and the in-built field of the Ce/CN S-scheme heterojunction.