Chemical reduction of porous WO3 and TiO2 photoelectrocatalysts by atomic hydrogen

The donor properties of atomic hydrogen were exploited to chemically reduce nanoparticle-based WO3 and TiO2 electrodes giving rise to a n-type doping of the semiconductors. For this purpose, a reactor system allowing for meticulous materials processing under high vacuum conditions and for the controlled electrode transfer into an aqueous electrolyte was designed and hydrogen doping-induced activity-changes in water photooxidation were studied. The chemical reduction of monoclinic WO3 electrodes leads to increased charge carrier separation at the semiconductor/electrolyte interface. Importantly, the beneficial doping effect is quite stable. However, bronze formation has a negative impact on the photoelectrocatalytic activity of WO3 electrodes upon strong sample reduction. For anatase TiO2 nanoparticle films de-doping of the reduced film is fast due to the small particle size. Correspondingly, the beneficial doping effect is transient. The small particle size allows, however, to estimate the number and energetic distribution of trapped electrons in hydrogen doped films.

Automated summary

The donor properties of atomic hydrogen were used to chemically reduce nanoparticle-based WO3 and TiO2 electrodes, resulting in n-type doping of the semiconductors. A reactor system was designed to allow meticulous materials processing under high vacuum conditions and controlled electrode transfer into an aqueous electrolyte. The activity changes in water photooxidation induced by hydrogen doping were studied. The reduction of monoclinic WO3 electrodes led to increased charge carrier separation at the semiconductor/electrolyte interface. However, bronze formation had a negative effect on the photoelectrocatalytic activity of WO3 electrodes when strongly reduced. For anatase TiO2 nanoparticle films, the de-doping of the reduced film was fast due to the small particle size. The beneficial doping effect was transient. Nonetheless, the small particle size allowed for the estimation of the number and energetic distribution of trapped electrons in hydrogen-doped films.