Trapping of Intermediates of a Photocatalytic Oxygen Evolution Reaction in Overall Water Splitting
Fumiaki Amano, Satoshi Nakayama, Souta Suzuki, Akira Yamakata, Kosuke Beppu
Abstract
Intermediates in the overall water splitting on particulate photocatalysts were investigated by electron paramagnetic resonance (EPR) measurements using 5,5-dimethyl-1-pyrroline N -oxide (DMPO) as a spin trap. In situ EPR spectra under ultraviolet light showed the exclusive formation of a hydroxyl radical adduct ( • DMPO-OH) over Ga 2 O 3 and NaTaO 3:La without a Rh–Cr oxide cocatalyst. In contrast, the Rh–Cr oxide cocatalyst-loaded photocatalysts active for water splitting formed a 5,5-dimethyl-2-oxo-pyrroline-1-oxyl radical ( • DMPOX). • DMPOX is suggested as an indicator of the surface peroxyl radical intermediate (M-OO • ) in the oxygen evolution reaction pathway.