A series of TiO2, TiO2/Pd, and TiO2/PdO hollow sphere photocatalysts was successfully prepared via a combination of hydrothermal, sol-immobilization, and calcination methods. The structure and optical properties of the as-prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Telleranalysis, Barrett-Joyner-Halenda measurement, and UV-Vis diffuse reflectance spectroscopy. The photocatalysis efficiencies of all samples were evaluated through the photocatalytic degradation of rhodamine B under visible light irradiation. Results indicated that TiO2/PdO demonstrated a higher photocatalytic activity (the photocatalytic degradation efficiency could reach up to 100% within 40 min) than the other samples and could maintain a stable photocatalytic degradation efficiency for at least four cycles. Finally, after using different scavengers, superoxide and hydroxyl radicals were identified as the primary active species for the effectiveness of the TiO2/PdO photocatalyst.

中文翻译：

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TiO2/Pd和TiO2/PdO空心球的合成及其可见光光催化活性

采用水热法、溶胶固定化法和煅烧法相结合的方法成功制备了一系列TiO2、TiO2/Pd和TiO2/PdO空心球光催化剂。通过X射线衍射、场发射扫描电子显微镜、透射电子显微镜、Brunauer-Emmett-Teller分析、Barrett-Joyner-Halenda测量和UV-Vis漫反射光谱表征所制备样品的结构和光学性质。通过在可见光照射下对罗丹明B的光催化降解来评估所有样品的光催化效率。结果表明，TiO2/PdO 表现出比其他样品更高的光催化活性（40 分钟内光催化降解效率可达 100%），并且可以保持稳定的光催化降解效率至少四个循环。最后，在使用不同的清除剂后，超氧化物和羟基自由基被确定为 TiO2/PdO 光催化剂有效性的主要活性物质。