Investigations on the stability of titanium dioxide ( TiO 2)-coated zinc oxide (ZnO) thin films upon repeated uses for methylene blue (MB) degradation were conducted. Photocorrosion of ZnO, upon exposure to light in aqueous media, can affect the photocatalytic performance due to loss of material. Hence, coating with a more stable metal oxide was seen as a way to suppress the effects of photocorrosion. In this study, homogeneous wurtzite ZnO nanostructured thin films were obtained from thermal oxidation of sputter-deposited Zn films on glass substrates. TiO 2 was subsequently deposited onto the ZnO nanostructured thin films using a reactive magnetron sputtering system in an admixture of argon and oxygen gases. After deposition, the thin films were annealed at 500 °C for 1 h. The photocatalytic efficiency and stability of the thin films were investigated after multiple degradation cycles. The addition of a TiO 2 film increased the surface roughness and blueshifted the absorption edge of the ZnO thin films. The coated films obtained up to 94.3% degradation efficiency of MB after a 180-min exposure cycle using a solar light simulator. After three cycles, degradation efficiency decreased for the uncoated ZnO photocatalysts. Analysis of the MB solution after one degradation cycle revealed the presence of Zn 2 + ions attributed to the effects of photocorrosion. Higher Zn 2 + concentrations were observed when the ZnO surface is uncoated. This study showed that the addition of a thin, antiphotocorrosion material such as TiO 2 layer decreased the dissolution of ZnO caused by photocorrosion without a significant reduction in the photodegradation efficiency.

中文翻译：

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TiO2包覆的ZnO光催化薄膜对亚甲基蓝光降解的稳定性

对二氧化钛 (TiO 2) 涂层氧化锌 (ZnO) 薄膜在重复使用亚甲蓝 (MB) 降解时的稳定性进行了研究。氧化锌的光腐蚀，在水介质中暴露在光线下时，会由于材料的损失而影响光催化性能。因此，用更稳定的金属氧化物涂层被视为抑制光腐蚀影响的一种方式。在这项研究中，从玻璃基板上溅射沉积的 Zn 薄膜的热氧化获得了均匀的纤锌矿 ZnO 纳米结构薄膜。随后使用反应性磁控溅射系统在氩气和氧气的混合物中将 TiO 2 沉积到 ZnO 纳米结构薄膜上。沉积后，薄膜在 500°C 下退火 1 小时。在多次降解循环后研究了薄膜的光催化效率和稳定性。TiO 2 薄膜的添加增加了表面粗糙度并使ZnO薄膜的吸收边蓝移。在使用太阳光模拟器进行 180 分钟的曝光循环后，涂层薄膜获得了高达 94.3% 的 MB 降解效率。三个循环后，未涂覆的 ZnO 光催化剂的降解效率降低。在一个降解循环后对 MB 溶液的分析表明存在 Zn 2 + 离子，这归因于光腐蚀的影响。当 ZnO 表面未涂覆时，观察到更高的 Zn 2 + 浓度。这项研究表明，加入一种薄的、