Construction of SnO2/g-C3N4 composite photocatalyst with enhanced interfacial charge separation and high efficiency for hydrogen production and Rhodamine B degradation

Abstract

SnO2/g-C3N4 heterostructure composites as effective photocatalysts were prepared by a simple calcination process with commercially available tin dioxide and melamine as precursors. The pure semiconductors as well as various compositions of SnO2/g-C3N4 heterostructure composites were characterized by powder X-ray diffraction (XRD), transmission and high transmission electron microscope (TEM, HRTEM), X-ray photoelectron spectroscopy (XPS), BET surface area, UV-Vis (DRS), and various electrochemical techniques to determine the physico-chemical properties. Photocatalytic activities of the SnO2/g-C3N4 composites with different mass percentages of SnO2 were evaluated for degradation of Rhodamine B under visible light irradiation and hydrogen production under light irradiation of λ ≥ 320 nm. The results verified that the composites were significantly developed compared to individual SnO2 and g-C3N4. XRD confirmed the existence of two phases in the SnO2/g-C3N4 heterostructure. TEM images showed that the spherical shaped SnO2 nanoparticles were distributed on the surface of the g-C3N4 sheets, and the construction of a heterojunction structure was identified by the HRTEM. Decreased optical band gap energy was revealed by the UV-Vis (DRS) experiments. Importantly, the photoelectrochemical tests demonstrate that the charge separation between electrons and holes is effectively enhanced, which could be attributed to the heterojunction structure between the two components (SnO2, g-C3N4) suppressing the charge carrier recombination, and thus, improving the photoactivity. The optimal SnO2 content is determined to be 20% displaying about 5 and 8 times higher photocatalytic activity than pure SnO2 for degradation of RhB and hydrogen production, respectively.