Since the radicals involved are very short-lived, a spin trap, 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) was used, which reacts with these short-lived radicals to form stable DMPO-radical adducts. EPR spectra were taken from samples that were irradiated ex situ in the presence of DMPO in a water-methanol mixture, under conditions similar to those used for photocatalytic H2O2 generation (detailed in the experimental section).