Ultrafast Charge Carrier Dynamics and Photoelectrochemical Properties of Hydrogen-treated TiO2 Nanowire Arrays

Abstract

ABSTRACTHere we report studies of photoelectrochemical (PEC) properties and ultrafast charge carrier relaxation dynamics of hydrogen-treated TiO2 (H:TiO2) nanowire arrays. PEC measurements showed the photocurrent density of the H:TiO2 was approximately double that of TiO2, attributed to increased donor density due to the formation of oxygen vacancies in H:TiO2 due to hydrogen treatment Charge carrier dynamics of H:TiO2, measured using fs transient absorption spectroscopy, showed a fast decay of ∼20 ps followed by slower decay persisting to tens of picoseconds. The fast decay is attributed to bandedge electron-hole recombination and the slower decay is attributed to recombination from trap states. Visible absorption is attributed to either electronic transitions from the valence band to oxygen vacancy states or from oxygen vacancy states to the conduction band of the TiO2, which is supported by incident photon to current conversion efficiency (IPCE) data. H:TiO2 represents a unique material with improved photoelectrochemical properties for applications including PEC water splitting, solar cells, and photocatalysis.