An Unusual Strong Visible-Light Absorption Band in Red Anatase TiO2 Photocatalyst Induced by Atomic Hydrogen-Occupied Oxygen Vacancies

Abstract

Increasing visible light absorption of classic wide-bandgap photocatalysts like TiO₂ has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry of these photocatalysts is essential to narrow their bandgap for a strong visible-light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail-like absorption band in hydrogen-free oxygen-deficient TiO₂, an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO₂ by intentionally introducing atomic hydrogen-mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo-electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide-bandgap semiconductors to fully capture solar light.

In contrast to the common tail-like absorption band in hydrogen-free oxygen-deficient TiO₂, an unusual strong absorption band spanning the full spectrum of visible light is achieved in red anatase TiO₂ by intentionally introducing atomic hydrogen-mediated oxygen vacancies that subsequently lead to active photo-electrochemical water oxidation under visible light.

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