Rationally designed C3N4/ TiO2 (anatase/brookite) heterojunction for enhanced photocatalytic hydrogen generation under visible light

Abstract

In this study, C3N4 was prepared using the polycondensation method, and TiO2 (ansate/Brookite) was synthesized using the solvothermal method. These materials were subsequently utilized to prepare C3N4/TiO2 heterojunction materials via the photoanchoring method, with the aim of improving photocatalytic hydrogen production. The physical, chemical, and optical properties of the composites were investigated to verify the formation of heterojunctions, as well as to assess the impact of varying levels of C3N4 content (1%, 5%, and 10%) in the C3N4/TiO2 composite on hydrogen production. Notably, the composite with 5% C3N4 demonstrated superior photocatalytic hydrogen production (approximately 692 μmol h-1 g-1), and the underlying reasons were elucidated using photoelectrochemical characterization. To establish the band alignment of C3N4 and TiO2 before and after contact, a comprehensive array of techniques was employed, encompassing Kelvin force microscopy to acquire work functions, UV–Vis spectral analysis to ascertain band gaps, XPS valence spectra to identify the Valence Band Maxima, and the Kraut method to calculate Band Offsets. These analyses revealed that the formation of the heterojunction is staggered in nature. Finally, utilization of ESR analysis has conclusively verified that the charge transfer mechanism inherent in the C3N4/TiO2 heterojunction adheres to the Z-scheme.