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

•The sol-gel process allows the formation of brookite and Cu2O oxide.•The Ti-Cu 1.0/500 have the highest Cu1+/Cu2+ and optimal brookite/anatase ratio.•Cu2O enhances the H2 production due to correlation between Eg and redox potentials.•Ti-Cu 1.0/500 photocatalyst shows the highest H2 production without Cu lixiviation.•Cu catalysts represents a cost saving of 124 times in contrast with the noble metals.

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.