Tightly Interfaced Cu2O with In2O3 to Promote Hydrogen Evolution in Presence of Biomass-Derived Alcohols

By a mild and straightforward synthetic protocol in aqueous solution and without surfactants, hierarchical Cu₂O nanospheres were grown on preformed In₂O₃ nanostructures, varying the ratio In : Cu (2.5, 0.5). Accordingly, two different binary compounds In₂O₃-Cu₂O were prepared and afterwards they were integrated with TiO₂ NPs. The ternary composites having a loading of 2.0, 5.0 and 10.0 wt.% respectively of binary In₂O₃-Cu₂O, were tested as photocatalysts in the solar-driven production of hydrogen from water, using as sacrificial agents alcohols derived from the biomass. Satisfyingly, the rate of H₂ evolution (20.5 mmol/g h) resulted two orders of magnitude higher respect to bare TiO₂ (0.2 mmol/g h). Electrochemical impedance spectroscopy and photoluminescence measurements revealed the formation of a tight heterojunction between In₂O₃ and Cu₂O, which is responsible for the improved charge carrier density and transfer and for the diminished electron-hole recombination.