Fabrication of BiVO4/Ag2CrO4 heterojunction composites modified with graphene oxide for enhanced photoelectrochemical and photocatalytic performance†

A novel GO/BiVO₄/Ag₂CrO₄ heterojunction photocatalyst was prepared by depositing Ag₂CrO₄ on the highly active (040) facet of BiVO₄, followed by incorporating graphene oxide (GO) through an in situ precipitation method. This synergistic modification of BiVO₄ by Ag₂CrO₄ and GO results in excellent photocatalytic performance, with a degradation efficiency of 94.6% coupled with a maximum rate constant of 0.223 min⁻¹, which is 2.40, 2.19 and 0.66 times higher than that of BiVO₄, Ag₂CrO₄, and BiVO₄/Ag₂CrO₄, respectively, for the degradation of ciprofloxacin (CIP) under visible light irradiation. The degradation efficiency of ciprofloxacin was evaluated using total organic carbon (TOC) analysis. Under investigated conditions, the GO/BiVO₄/Ag₂CrO₄ photocatalyst achieved a TOC reduction of 63.4%. The enhanced photocatalytic performance is attributed to the beneficial role of GO in facilitating electron transport for photo-charge carrier migration, leading to strong interfacial coupling between BiVO₄ and Ag₂CrO₄, which in turn promotes efficient charge separation and transfer. The physicochemical properties of the fabricated heterojunction photocatalysts were characterized using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) coupled with energy-dispersive X-ray (EDX) analysis, Brunauer–Emmett–Teller (BET) analysis, Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) emission spectroscopy, while the photoelectrochemical properties of the fabricated photocatalyst were investigated through electrochemical impedance spectroscopy (EIS), Mott–Schottky plots, and photocurrent response analysis. The scavenging experiment was conducted to confirm the role of H⁺ and ·O₂⁻ in the photocatalytic degradation of ciprofloxacin, which aids in proposing probable degradation mechanism for ciprofloxacin under visible light irradiation. Hence, this study offers an effective strategy for fabricating heterojunction photocatalysts aimed at enhancing the photodegradation of pollutants in wastewater.