A simple one-pot synthesis of a Zn(O,S)/Ga2O3 nanocomposite photocatalyst for hydrogen production and 4-nitrophenol reduction

Abstract

Noble metal-free Zn(O,S)/Ga₂O₃ nanocomposite photocatalysts containing different amounts of Ga₂O₃ have been synthesized using a precipitation method at 90 °C. The as-prepared catalysts were characterized and their composite nature was confirmed. The Zn(O,S)/Ga₂O₃ catalysts were examined for their ability to evolve hydrogen under low UV light illumination (0.088 mW cm⁻²) and to provide hydrogen for 4-nitrophenol (4-NP) reduction. Gas chromatography measurements revealed that hydrogen was produced at a rate of 280 μmol g⁻¹ h⁻¹ W⁻¹, while UV-vis absorption and high-performance liquid chromatography (HPLC) measurements confirmed the formation of 4-aminophenol (4-AP) as a product of 4-NP reduction. The heterojunction formation between the Zn(O,S) and Ga₂O₃ phases enhanced the photocatalytic activity, compared to the single Zn(O,S) and Ga₂O₃ phases. Surface oxygen anions and oxygen vacancies played important roles in the photocatalytic mechanism to evolve hydrogen and to utilize hydrogen ions in 4-NP reduction. The photocatalytic hydrogen evolution reaction and its utilization for 4-NP reduction to 4-AP were evaluated and elucidated in this work.