Thermally assisted in situ synthesis of C3N5/TiO2 S-scheme heterojunctions with enhanced visible light response for photocatalytic hydrogen precipitation

Abstract

Nitrogen-rich C3N5 has emerged as a promising visible light catalyst due to its narrow band gap. Nevertheless, its practical application is hindered by the rapid recombination of photogenerated carriers. To address this limitation and enhance the photocatalytic performance of C3N5-based photocatalysts, one effective measure involves the construction of heterojunctions in conjunction with other semiconductors. In this work, the C3N5/TiO2 S-scheme photocatalysts was constructed by matching C3N5 with a more negative conduction band (CB) and TiO2 with a more positive valence band (VB). Photoelectric tests exhibited that the prepared photocatalysts possessed enhanced visible light photoresponsivity as well as excellent charge separation and transport efficiencies. The characterization results of XPS and EPR confirmed that the existence of internal electric field and the unique S-scheme charge transfer mechanism, which achieves overall spatial separation of effective photogenerated carriers and accelerates the recombination of redundant electrons and holes. The photocatalytic hydrogen production performance of the TCN2 is 6.9 times and 30 times higher than that of C3N5 and TiO2, respectively, which is ascribed to the unique charge transfer mechanism of the S-scheme heterojunction and significantly enhanced photocatalytic activity. The simple construction of S-scheme heterojunctions in this work provides a new strategy for research in other fields.