Hierarchical bismuth vanadate/reduced graphene oxide composite photocatalyst for hydrogen evolution and bisphenol A degradation

Bismuth vanadate (BiVO₄) is a widely studied photocatalyst for the depollution of contaminated wastewater, production of hydrogen by water splitting, and organic synthesis. The photophysical properties of BiVO₄ are sensitive to morphology and quantum confinement effects, and can exhibit enhanced photocatalytic performance in nanocomposites with graphene. Synthesis of hierarchical BiVO₄ plates decorated by nanoparticles (h-BiVO₄) in contact with reduced graphene oxide (RGO) is reported via a facile one-pot solution phase approach using ethanolamine and a polyethylene glycol stabilizer. The resulting h-BiVO₄/RGO photocatalyst exhibited superior photoactivity for bisphenol A (BPA) degradation and hydrogen evolution under visible light irradiation compared to single component h-BiVO₄ or a μm-sized block-like BiVO₄ morphology. Rates of BPA photocatalytic degradation and apparent quantum efficiency (AQE) decreased in the order h-BiVO₄/RGO (4.5 × 10⁻² mmol.g⁻¹.min⁻¹; 15.1% AQE) > h-BiVO₄ (3.5 × 10⁻² mmol.g⁻¹.min⁻¹; 11.7% AQE) > BiVO₄ (1 × 10⁻² mmol.g⁻¹.min⁻¹; 3.4% AQE), representing a 4.5 fold enhancement for h-BiVO₄/RGO versus BiVO₄. Liquid phase photodegradation products included benzene-1,4-diol, cyclohexa-2,5-diene-1,4-dione and (2Z)-but-2-enedioic acid. The rate of photocatalytic hydrogen production under visible light was 11.5 µmol.g^−1.h⁻¹ for h-BiVO₄/RGO, ~383.3 times greater than for BiVO₄ (0.03µmol.g⁻¹.h⁻¹). The superior photocatalytic performance of h-BiVO₄/RGO is largely attributed to its higher surface area, aided by enhanced visible light absorption and charge separation across the semiconductor-RGO interface, which together confer a higher density and lifetime of photoexcited charge carriers.