The amount of O 2 evolved due to catalytic degradation of H 2 O 2 by Pac-Man TiO 2 particles is measured by a self-designed drainage method inspired by Wang et al.. A schematic representation of the process is shown in supporting information (Figure ). For the experiment, a 1.5 mL quartz GC vial (from Nexus Company INC., Kyoto, Japan) is filled with 1 mL of a mixture of Pac-Man particles (1 g L -1 ) in H 2 O 2 (1%, or 2.5%, or 5%, or 10% (w/w)). The vial is then connected to a 1 mL glass gas syringe with a luer lock by a vial adapter and illuminated uniformly with UV LEDs (385 nm wavelength and intensity of around 250 mW cm -2 per LED (total 8 LEDs)). The amount of oxygen evolved is obtained by measuring the displacement of the piston in the glass syringe. At least 3 measurements are taken for each data point at a given H 2 O 2 concentration. The volume of oxygen evolved is plotted against average time with standard deviation. The volume error of the glass syringe is calculated by weighting the obtained liquid amounts.