Photocatalytic experiments were performed under LED UV-light irradiation (365 nm, 3.3 mW cm -2 ), LED violet-light irradiation (406 nm, 4.2 mW cm -2 ) or polychromatic visible light (~100 mW/cm 2 ) using an Ushio 150 W Xe lamp in a light-condensing lamp housing (LOT-Oriel GmbH) equipped with a >420 cut-off filter (Schott). If not stated otherwise, mixtures of 5 mL of water and 5 mL of benzyl alcohol containing certain amounts of benzaldehyde were vigorously stirred and irradiated. The temperature of 20 C in the photocatalytic reactors was maintained by a water-cooling jacket. Before irradiation started, the solutions were flushed with pure O2 and sealed with rubber septa. This procedure was repeated each time after taking the samples out from the reactors for analysis. The samples of 0.1 mL (diluted if necessary, as to fit the linear range of the calibration curve) were taken at certain time intervals, mixed with 2.4 mL of H2O and 0.5 mL of TiOSO4 solution to produce the yellow-coloured titanium peroxo complex. H2O2 concentration was estimated by measuring the absorbance of the titanium peroxo complex solutions at 420 nm using a Cary 60 (Agilent Technologies) spectrophotometer. The calibration curve was obtained using known concentrations of H2O2.