Sunlight-driven sustainable production of hydrogen peroxide using a CdS–graphene hybrid photocatalyst

We demonstrate the sustainable production of H₂O₂ without organic electron donors by a CdS-reduced graphene oxide (RGO) photocatalyst in sunlight with water and oxygen as resources. Photocatalysts were prepared with various amounts of RGO (0–30 wt.% with respect to CdS) by a hydrothermal method. A photocatalyst containing 20 wt.% RGO (CdS-G2) showed maximum activity, and the amount of H₂O₂ produced (128 μM) was almost five times higher than that produced by CdS nanoparticles (27 μM) after 12 h sunlight irradiation. The results clearly revealed that the photocatalytic reaction mainly proceeds by two-electron reduction of oxygen rather than water oxidation on the catalyst surface. The effects of reaction temperature and pH on the production of H₂O₂ were also investigated. We found that the production of H₂O₂ was enhanced at lower temperature and pH. The concentration of H₂O₂ reached to 164 and 156 μM with CdS-G2 at 10 °C and pH 2, respectively.