Abstract As an important semiconductor material for photocatalysis, zinc oxide (ZnO) has been prepared by various methods to enhance its photocatalytic activity. Herein, hierarchically porous ZnO microspheres were synthesized by hydrothermal treatment of precursor zinc salts and subsequent low-temperature (300 °C) calcination for 2 h, and the photocatalytic properties of the ZnO microspheres were examined by degrading Rhodamine B under simulated solar light. The type of the precursor zinc salts (nitrate, acetate, sulfate and chloride) had a great impact on the morphological, textural, optical and photoelectrochemical properties of the as-prepared ZnO microspheres, which collectively affected the photocatalytic performance. The as-prepared hexagonal wurtzite ZnO exhibits unique hierarchical porous microsphere morphology with diameters in the range of 3–6 μm. The photocatalytic activity of the ZnO microspheres also depended on the zinc precursor and followed the order: zinc sulfate > zinc nitrate > zinc acetate > zinc chloride. The high photocatalytic activity of ZnO microspheres prepared from zinc sulfate was due to its higher specific surface area (91 m2 g−1), better visible light absorption, more oxygen defects and higher charge separation and transfer efficiencies, as well as the hierarchical pore structure that promotes the diffusion of reactant molecules. Moreover, electron paramagnetic resonance spectroscopy identified hydroxyl radicals and superoxide radical anions as reaction intermediates, shedding light on the mechanism of the dye photodegradation reaction.

中文翻译：

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用于增强光催化活性的 ZnO 分级微球

摘要 氧化锌（ZnO）作为一种重要的光催化半导体材料，已通过多种方法制备以提高其光催化活性。在此，通过前体锌盐的水热处理和随后的低温（300℃）煅烧 2 小时合成了分级多孔 ZnO 微球，并通过在模拟太阳光下降解罗丹明 B 来检查 ZnO 微球的光催化性能。前体锌盐（硝酸盐、醋酸盐、硫酸盐和氯化物）的类型对所制备的 ZnO 微球的形态、结构、光学和光电化学性质有很大影响，共同影响了光催化性能。所制备的六方纤锌矿 ZnO 表现出独特的分级多孔微球形态，直径范围为 3-6 μm。ZnO微球的光催化活性也取决于锌前驱体，其顺序为：硫酸锌>硝酸锌>醋酸锌>氯化锌。由硫酸锌制备的 ZnO 微球的高光催化活性是由于其更高的比表面积 (91 m2 g-1)、更好的可见光吸收、更多的氧缺陷和更高的电荷分离和转移效率，以及分级孔结构促进反应物分子的扩散。此外，电子顺磁共振光谱确定羟基自由基和超氧自由基阴离子作为反应中间体，