Mediator-free direct Z-scheme photocatalytic system: BiVO4/g-C3N4 organic–inorganic hybrid photocatalyst with highly efficient visible-light-induced photocatalytic activity

Abstract

We disclose the fabrication of a mediator-free direct Z-scheme photocatalyst system BiVO₄/g-C₃N₄ using a mixed-calcination method based on the more reliable interfacial interaction. The facet coupling occurred between the g-C₃N₄ (002) and BiVO₄ (121), and it was revealed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). The crystal structure and optical properties of the as-prepared samples have also been characterized by Fourier-transform infrared (FTIR), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectra (DRS) in details. The photocatalytic experiments indicated that the BiVO₄/g-C₃N₄ composite photocatalysts display a significantly enhanced photocatalytic activity pertaining to RhB degradation and photocurrent generation (PC) compared to the pristine BiVO₄ and g-C₃N₄. This remarkably improved photocatalytic performance should be attributed to the fabrication of a direct Z-scheme system of BiVO₄/g-C₃N₄, which can result in a more efficient separation of photoinduced charge carriers than band–band transfer, thus endowing it with the much more powerful oxidation and reduction capability, as confirmed by the photoluminescence (PL) spectra and electrochemical impedance spectra (EIS). The Z-scheme mechanism of BiVO₄/g-C₃N₄ heterostructure was verified by a series of combined techniques, including the active species trapping experiments, NBT transformation and terephthalic acid photoluminescence probing technique (TA-PL) over BiVO₄/g-C₃N₄ composites and the pristine samples. The present work not only furthered the understanding of mediator-free Z-scheme photocatalysis, but also shed new light on the design of heterostructural photocatalysts with high-performance.