Illumination of anatase in an aqueous methanolic solution leads to the formation of Ti 3 + sites that are catalytically active for the generation of dihydrogen (H 2 ). With increasing illumination time, al ight-induced self-amplification of the photocatalytic H 2 production rate can be observed. Thee ffect is characterized by electronp aramagnetic resonance (EPR) spectroscopy,r eflectivity,a nd photoelectrochemical techniques. Combined measurements of H 2 generation rates and in situ EPR spectroscopic observation over the illumination time with AM 1.5G or UV light establish that the activation is accompanied by the formation of Ti 3 + states, which is validated through their characteristic EPR resonancea tg = 1.93. This selfactivation and amplification behavior can be observed for anatase nanoparticles and nanotubes.
Herein we introduce for the first time a reduced “grey” brookite TiO2 photocatalyst, produced by thermal hydrogenation of brookite nanoparticles, that shows a remarkable noble metal free photocatalytic H2 evolution.
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