Silver oxidation state effect on the photocatalytic properties of Ag doped TiO2 for hydrogen production under visible light

•Ag doped TiO2 synthesized by sol–gel/solvothermal and sol–gel/solvothermal/thermal.•Ag as metal helps to prevent the direct recombination of electrons and holes.•Ag in TiO2 lattice enter in intermediate states to decrease TiO2 bandgap energy.•Ag doped TiO2 sol–gel/solvothermal produced 180 μmol H2/gcat under 4 h irradiation.

TiO2 is the most widely used photocatalyst. However, its bandgap energy is in the UV spectrum. Studies are concentrated to modify TiO2 bandgap into the visible range. Among doping elements used is Ag. Undoped and doped TiO2 were synthesized via sol–gel/solvothermal (SGH) named TiO2–F and TiO2Ag–F, respectively, while under the sol–gel/solvothermal/thermal (SGHT) technique was named as TiO2Ag–C. XRD results shown only anatase phase in all samples and characteristic signals for metallic Ag in TiO2Ag–F. Samples crystal sizes were ∼10 nm. A shift in the Eg value from 3.05 eV to 2.8 eV for TiO2 samples occurred. BET surface area for the SGH and SGHT photocatalysts were of 140 and 95 m2/g, respectively. SEM images presented agglomerates of irregular morphology. Photocatalytic evaluation for hydrogen production employed a 250 W UV-filtered mercury lamp. TiO2Ag–F was the only sample that showed activity, producing 180 μmol of H2/gcat under 4 h irradiation.