Gas phase photocatalytic decomposition of alcohols with titanium dioxide nanotube arrays in high vacuum

Hydrogen production based on gas-phase photocatalysis was investigated for platinized titanium dioxide (TiO₂) nanotube arrays (TNAs) in high vacuum. In the presence of ethanol of 10^-6 Torr, H₂ generated from the ethanol photodecomposition was successfully detected at a real-time scale for anodized TNAs. In addition, it was found that longer nanotube arrays with upright geometry are desirable for increasing the amount of the H₂ production. A mechanism of gas phase photocatalytic reforming for the TNAs, considered in this work, suggests that the selective deposition of Pt cocatalyst particles on the aperture parts of the nanotube arrays is necessary for efficient H₂ production. This consideration was confirmed by the experimental result of the comparison of different Pt deposition methods: RF sputtering and photodeposition. These findings obtained in this study will be useful for designing new hydrogen reformers in the future.