Enhanced photoelectrochemical (PEC) and photocatalytic properties of visible-light reduced graphene-oxide/bismuth vanadate

Highlights: • Photocatalytic reduction of GO produced complete coverage of BVO by rGO sheets. • Photodegradation of MB and TC was 2-fold greater than that using BVO. • Photocurrent density of BVO/rGO (133 µA cm⁻²) was greatly increased compared to that of BVO (21 µA cm⁻²). • BVO/rGO photoelectrode exhibited a very high stability of 90% even after 2400 s. • Charge recombination time of BVO/rGO (11 s⁻¹) was greatly increased compared to that of BVO (5 s⁻¹). A simple visible-light-assisted photocatalytic reduction of graphene oxide (GO) to reduced graphene oxide (rGO) using BiVO₄ (BVO) in BVO/GO was designed to remarkably improve the photocatalytic degradation and photoelectrochemical (PEC) water splitting efficiencies of BVO. The resulting smaller particle size and strong interfacial interaction on the graphene sheet of the prepared BVO/rGO nanocomposite (NC) enhanced the photocatalytic degradation of tetracycline (TC) and methylene blue (MB) from aqueous solution, and also PEC water splitting. The photocatalytic degradation of MB and TC from aqueous solution using BVO/rGO was enhanced almost 2-fold compared to using BVO with complete photodegradation being achieved in 60 and 55 min of visible-light irradiation, respectively. The photocurrent onset potential of BVO/rGO was negatively shifted by −0.2 V vs. Ag/AgCl. The photocurrent density of BVO/rGO was greatly improved to 133 µA cm⁻² at 0.8 V vs. Ag/AgCl, as compared to 21 µA cm⁻² with BVO. The charge recombination time was greatly increased from 5 s⁻¹ for BVO to 11 s⁻¹ for BVO/rGO. The BVO/rGO photoanode exhibited long-term operation stability by maintaining 90.2% of the initial photocurrent density after 2400 s, while BVO showed poor stability of 65.1%. The great improvement of photocatalytic (2.0-fold) and PEC water splitting activity (6.3-fold) in BVO/rGO was attributed to the longer electron lifetime (2.2-fold), enhanced carrier concentration (5.87-fold), reduced interfacial electron transfer resistance, excellent stability and reusability, reduced particle size, and extended photoresponse range, which were derived from the ultimate coverage of BVO by rGO.