Enhanced hydrogen generation using ZrO2-modified coupled ZnO/TiO2 nanocomposites in the absence of noble metal co-catalyst

Mesoporous ZrO2-modified coupled ZnO/TiO2 nanocomposites were prepared by a surfactant assisted sol–gel method. The photocatalytic performance of these materials was investigated for H2 evolution without noble metal co-catalyst using aqueous methanol media under AM1.5 simulated light. The H2 evolution was compared with coupled ZnO/TiO2, TiO2, ZnO and Degussa P25. The ZrO2-modified nanocomposites exhibited higher H2 generation, specifically 0.5 wt.% ZrO2 loading produced 30.78 mmol H2 g−1 compared to 3.55 mmol H2 g−1 obtained with coupled ZnO/TiO2. A multiple absorbance thresholds at 435 nm and 417 nm were observed with 0.5 wt.% ZrO2 loading, corresponding to 2.85 eV and 2.97 eV band gap energies. The high surface area, large pore volume, uniform crystallite sizes and enhanced light harvesting observed in ZrO2-modified nanocomposites were contributing factors for effective charge separation and higher H2 production. The possible mechanism of H2 generation from aqueous methanol solution over ZrO2-modified nanocomposite is presented.