Unraveling the effect of low Cu₂O loading on P25 TiO₂ and its self-reduction during methanol photoreforming

Using noble metal-free catalysts is highly promising for sunlight-driven photocatalytic H₂ production. Copper compounds have gained considerable interest in this regard. Cu₂O/semiconductor composites exhibit superior photocatalytic activity compared to individual compounds. This study focuses on different Cu_XO/TiO₂ composites synthesized via chemical reduction, using Cu₂O weight ratios ranging from 1 to 0.05 concerning the TiO₂ source. Characterization techniques were employed, including XRD, SEM, XPS, UV–Vis DRS, PL, and TRMC. Surface modification of TiO₂ with Cu species (CuO, Cu₂O, and Cu⁰) was observed during the photocatalytic reforming of methanol under simulated solar light. By loading small amounts of Cu_XO (0.05–0.1%) on TiO₂, the highest H₂ production and methanol mineralization were achieved, along with the formation of metallic copper. The coexistence of the Cu species and TiO₂ facilitated the effective separation of photogenerated electrons and holes, promoting the photoreduction of protons and photooxidation of methanol, respectively.