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

Abstract By a mild and straightforward synthetic protocol in aqueous solution and without surfactants, hierarchical Cu 2 O nanospheres were grown on preformed In 2 O 3 nanostructures, varying the ratio In : Cu (2.5, 0.5). Accordingly, two different binary compounds In 2 O 3 ‐Cu 2 O were prepared and afterwards they were integrated with TiO 2 NPs. The ternary composites having a loading of 2.0, 5.0 and 10.0 wt.% respectively of binary In 2 O 3 ‐Cu 2 O, 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 H 2 evolution (20.5 mmol/g h) resulted two orders of magnitude higher respect to bare TiO 2 (0.2 mmol/g h). Electrochemical impedance spectroscopy and photoluminescence measurements revealed the formation of a tight heterojunction between In 2 O 3 and Cu 2 O, which is responsible for the improved charge carrier density and transfer and for the diminished electron‐hole recombination.