Hydrogen production by tailoring the brookite and Cu2O ratio of sol-gel Cu-TiO2 photocatalysts

Abstract

Cu-TiO₂ photocatalysts were prepared by the sol-gel method. Copper loadings from, 1.0 to 5.0 wt % were used. The materials were annealed at different temperatures (from 400 to 600 °C) to study the formation of brookite and copper ionic species. The photocatalysts were characterized by X-ray diffraction, UV-vis, Raman and XPS spectroscopies, H₂-temperature programmed reduction (TPR), N₂ physisorption, and SEM-EDS to quantify the actual copper loadings and characterize morphology. The photocatalysts were evaluated during the hydrogen photocatalytic production using an ethanolic solution (50% v/v) under UV and visible radiation. The best hydrogen production was performed by Ti-Cu 1.0 with an overall hydrogen production that was five times higher than that obtained with photolysis. This sample had an optimal thermal treatment at 500 °C, and at this temperature, the Cu₂O and brookite/anatase ratio boosted the photocatalytic production of hydrogen. In addition, a deactivation test was carried out for the most active sample (TiO₂-Cu 1.0), showing unchanged H₂ production for three cycles with negligible Cu lixiviation. The activity of hydrogen-through-copper production reported in this research work is comparable with the one featured by noble metals and that reported in the literature for doped TiO₂ materials.

Keywords: Anatase – brookite ratio; Copper lixiviation; Cu(2)O; Cu-TiO(2); Cyclic H(2) production; Water splitting.