Engineering the heterojunction between TiO2 and In2O3 for improving the solar-driven hydrogen production

Nanostructured In2O3 was grown on TiO2 NPs by thermal treatment of the solids mixture of TiO2 with the parent In(OH)3. The effect of calcination temperature in the range between 400 °C and 700 °C was investigated and peculiar changes both in the structure and in the catalytic activity of the TiO2/In2O3 heterostructure were revealed. It was found out that T = 600 °C is the best operating temperature for hydrogen production and in combination with 3.5 wt% In2O3 the H2 production from water reached the value of 3.5 mmol/h.g irradiating in the UV-Vis region. Once 5.0 wt% Cu2O nanoparticles were loaded on TiO2/In2O3, the photocatalytic activity boosted to 9.6 mmol/h.g of H2, overcoming the hydrogen production of pristine TiO2 by a factor of 48. This result can be attributed to the formation of a highly efficient heterojunction that assures a synergistic cooperation among the three semiconductors yielding an improved charge separation and faster charge transport, as evidenced by Mott-Schottky, PL and EIS measures.