Novel ZnS-ZnO composite synthesized by the solvothermal method through the partial sulfidation of ZnO for H₂ production without sacrificial agent

Novel ZnS-ZnO composites were synthesized by the solvothermal method from the partial sulfidation of ZnO using thiourea at low temperatures. The synthesized materials were active for the photocatalytic production of H₂ with and without the presence of sacrificial agent without the addition of a co-catalyst; in the present paper, methanol was evaluated as sacrificial agent, increasing the amount of H₂ produced up to five times compared to the most active photocatalyst without using sacrificial agent. All the materials were characterized by XRD, N₂ Physisorption, FT-IR, XPS, Diffuse Reflectance Spectroscopy, and HR-TEM. In addition, the materials were characterized by photo-electrochemical techniques to explain the photocatalytic behavior. The most active material was the composite with an atomic ratio of S/Zn = 0.71 synthesized at 100 °C, producing 247 μmol H₂ h⁻¹ g⁻¹, the H₂ production rate was improved five times with the addition of methanol as sacrificial agent. The improvement of the photocatalytic activity was attributed to the formation of the heterojunction at the interface formed between ZnO and ZnS, promoting a higher electron transfer to the conduction band and a lower charge transfer resistance from the catalyst surface to the solution reaction.