Over the past years, so‐called water annealing of TiO₂ nanotube (NT) arrays has attracted considerable attention as a tool to enhance the nanotubes’ photocatalytic properties. The present work investigates the effect of different water‐annealing treatments on TiO₂ nanotubes and compares it to thermally annealed tubes. We find that the most effective water annealing is water immersion of TiO₂ NT arrays at 70 °C for several days. The two main effects are i) a partial crystallization of the tubes to anatase, and ii) an etching of the tube walls that leads to a roughening of the walls and, thus, to a higher surface area. Under the best conditions, water annealing is almost as effective in providing enhanced photocatalytic AO7 degradation as a classic thermal annealing of the tubes. We, however, find that water annealed tubes – due to their only partial crystallization – do not perform well when used as photoelectrodes. For photocatalysis, most efficient is a combination of water annealing, followed by thermal annealing, which provides both a larger surface area and a high crystallinity.

中文翻译：

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TiO2纳米管光催化水退火的再探讨。

在过去的几年中，所谓的TiO ₂纳米管（NT）阵列的水退火作为一种增强纳米管光催化性能的工具已经引起了广泛的关注。本工作研究了不同的水退火处理对TiO ₂纳米管的影响，并将其与热退火管进行了比较。我们发现最有效的水退火是TiO _2的水浸NT阵列在70°C下放置几天。两个主要作用是：i）使管部分结晶为锐钛矿； ii）蚀刻管壁，导致壁变粗糙，从而导致更大的表面积。在最佳条件下，水退火在增强光催化AO7降解方面几乎与传统的管子热退火一样有效。但是，我们发现水退火管-仅由于其部分结晶-在用作光电极时效果不佳。对于光催化，最有效的方法是先进行水退火，再进行热退火，这既提供了较大的表面积，又提供了高结晶度。