Reduced graphene oxide/ bismuth tungstate-based photocatalysts for enhanced dye photodegradation and photoelectrochemical water splitting

Semiconductor-based heterogeneous photocatalysis generates highly reactive charge carriers under solar illumination, making it a successful approach for wastewater purification and energy production applications. Herein, a simple solvothermal approach was used to generate a promising nanocomposite photocatalyst, reduced graphene oxide/bismuth tungstate (rGO/Bi₂WO₆). Various analytical tools were utilized to characterize the as-prepared catalysts. The oxidation of methylene blue (MB) and rhodamine B (RhB) dyes in the presence of solar light was performed to assess the photocatalytic activity of the rGO/Bi₂WO₆ combination. Also, photoelectrochemical (PEC) water splitting as an efficient and cost-effective way of producing hydrogen from water using solar energy is tested. The effect of the calcination temperature of Bi₂WO₆ and the amounts of graphene oxide on the catalytic activity was studied. After 30 minutes of exposure, the synthesised 10rGBW calcined at 700 °C (10rGBW-IV) showed good photodegradation percentages of 100.0% and 87.6% for MB and RhB dyes, respectively. Also, the larger photocurrent response intensity and lower arc radius of the electrochemical impedance of rGO/Bi₂WO₆ compared to Bi₂WO₆ revealed the synergistic effect on Bi₂WO₆ visible light responsiveness. According to the Mott-Schottky curve, 10rGBW-IV demonstrates a larger negative shift of the Fermi level (FB = -0.08 V <i>versus</i> RHE), indicating a stronger oxidation potential for water splitting.