Photoresponse of n-type semiconductor NiTiO3

Abstract
The 60‐Hz photocurrent of 103‐Ω cm, Nb‐doped n‐TiO3 has been measured by lock‐in amplification as a function of wavelength and applied potential. NiTiO3 is oxidized anodically in the dark producing Ni2+ ions in solution; however, this corrosion is but a fraction of the total charge passed either with visible or UV light, which indicates that photogenerated holes are able to oxidize water. The spectral response is shifted towards the visible region, as compared with TiO2, and the flatband potential is 0.4 V more negative than that of the H+/H2 redox couple, which would make possible the use of NiTiO3 for water photoelectrolysis. However, the quantum efficiency for visible light is much lower than that for UV light, primarily because of a low oscillator strength for the visible light Ni2+‐Ti4+ charge‐transfer excitation in this structure.

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