Enhanced V_O^•• sites with substitutional defects of Li_Zn^′ on Zn(O,S) for high-rate hydrogen generation under simulated solar-light irradiation

Carbon-free fuels are required to meet the net-zero emission in 2050 and hydrogen fuel is promising as the future solution. In this work, the hydrogen-evolved Zn(O,S) photocatalyst is improved by doping Li into its lattice with different amounts of LiNO₃ precursor. The single phase of Li-doped Zn(O,S) has been confirmed with XRD and TEM analysis. In addition, the electrochemical and optical properties of catalysts are studied with EIS, TPC, DRS, and PL analyses. Li-ZnOS-10 exhibits interesting behaviors with a lower charge transfer resistivity, good photoresponse, and lower PL emission, suggesting it is a promising photocatalyst material. The as-prepared catalysts are tested for hydrogen generation reaction with simulated solar-light illumination. Li-ZnOS-10 catalyst can produce ∼15 mmol/gh and convert 30 ppm nitrobenzene to aniline entirely in 3 h. XPS analysis indicates a low amount of Li dopant in Zn(O,S), implying the formation of Li_Zn⁻ surface defect that attracts the H⁺ to longer its lifetime for hydrogenation reaction. Furthermore, the indicated oxygen vacancy sites (V_O²⁺) also play a crucial role in interacting with nitrobenzene and trapping electrons during photoreaction. This work demonstrated improved hydrogen generation reaction and the possible application for green chemical conversion.