Calcination synthesis of tin niobate loaded porous carbon nitride S-scheme heterojunction for photocatalytic H2 production and tetracycline degradation

Abstract

The fabrication of heterojunctions with large interfacial contact areas is an effective technique for the development of high-performance photocatalysts. Step-scheme (S-scheme) heterojunctions with enhanced charge separation and strong redox ability have been regarded as promising photocatalytic materials in recent years. Herein, an S-scheme heterojunction based on tin niobate nanosheets and porous carbon nitride was designed and constructed using a one-plot calcination method. The multifunctional photocatalyst showed greatly enhanced photocatalytic activity and outstanding chemical stability toward hydrogen evolution and tetracycline hydrochloride (TCH) degradation, with reaction rates 1.64 and 12.28 times higher for TCH degradation and H2 production, respectively, compared to those of pristine g-C3N4. Meanwhile, TCH degradation experiments at different pH, TCH concentrations, catalyst dosages, and anions were evaluated. The main reactive species, possible degradation intermediates, and pathways were determined. The heterojunction exhibited a high surface area and broad visible-light absorption, which are responsible for the improved photocatalytic performance and high apparent quantum yield (AQY). In addition, an S-scheme charge transfer mechanism under an internal electric field was proposed following the results of in-situ irradiation X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), ESR, and Mott-Schottky measurements. This study offers a reasonable way to design another novel 2D/2D S-scheme heterojunction photocatalysts for energy and environmental applications.