One-pot preparation of multicomponent photocatalyst with (Zn, Co, Ni)(O, S)/Ga2O3 nanocomposites to significantly enhance hydrogen production

Abstract

To enhance the production of hydrogen as an alternative energy to fossil fuel, multicomponent photocatalyst (Zn, Co, Ni)(O, S)/Ga₂O₃ nanocomposites were synthesized and optimized with different amounts of Ga precursor in a relatively low-temperature process. The as-prepared nanocomposites were characterized by XRD, SEM, TEM, XPS, DRS, PL, EIS, TPC, CV, and MS techniques, and tested for their photocatalytic activities toward hydrogen evolution reactions (HERs). Zn(O, S) phase formation with low amounts of Ni and Co dopants and a Ga₂O₃ secondary phase were confirmed. The HER catalytic activity of the as-prepared nanocomposite could achieve ∼9 mmol g⁻¹ h⁻¹ without any noble metal as a cocatalyst under low-power UV-light-illuminated conditions. Ethanol was used as the hole scavenger to enhance the photocarrier separation during the photocatalytic HER. It was found that Ni–Co codopants played an essential role in improving HER activities of Zn(O, S). Although the wide-bandgap Ga₂O₃ is not active for photoexcitation under 365 nm light irradiation, it is believed that oxygen vacancies in Ga₂O₃ induce the electron transfer from the conduction band of (Zn, Ni, Co)(O, S). This charge transfer contributes to the photocarrier separation, leading to a higher photocatalytic activity. Moreover, based on XPS results, the trivalent Ni dopant also generated positively charged antisite defects, which also helps electron trapping, reducing the electron–hole recombination rate. This work demonstrated a nanomaterial-design strategy involving simultaneously using dopants and nanocomposite concepts to enhance hydrogen production with an aim to solve the global energy issue.