The synthesis of ZnO photocatalysts by ultrasound-assisted technique was here investigated. Several experimental parameters including the zinc precursor (acetate, chloride, nitrate), sonication conditions (amplitude, pulse) and post-synthetic thermal treatment (up to 500 °C) were studied. Crystalline ZnO samples were obtained without thermal treatments due to the adopted reactant ratios and synthesis temperature. Sonication plays a major role on the morphological oxide features in terms of particle size and surface area, the latter showing a 20-fold increase with respect to conventional synthesis. Interestingly, 1 and 3 s sonication pulses led to morphological properties similar to continuous sonication. A thermal treatment at moderate temperatures (400-450 °C) promoted the loss of surface hydroxylation and the formation of lattice defects, while higher temperatures were detrimental for the sample morphology. The prepared ZnO was decorated with WO3 particles comparing an ultrasound-assisted technique using 1 s pulses with a conventional approach, giving rise to composites with promoted visible light absorption. Samples were tested towards the photocatalytic degradation of nitrogen oxides (500-1000 ppb) in humidified air under both UV and visible light. By carefully controlling the synthetic procedure, better performance were observed with respect to the commercial benchmark. Samples from ultrasound-assisted syntheses, also in the case of pulsed sonication, showed consistently better results than conventional references, in particular for ZnO-WO3 composites. The composite by ultrasound-assisted synthesis showed > 95% degradation in 180 min and doubled NOx degradation under visible light with respect to the conventional composite.

中文翻译：

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超声波辅助氧化锌光催化剂的气相污染修复：合成参数的作用以及WO3的促进作用。

本文研究了超声辅助合成ZnO光催化剂的方法。研究了几个实验参数，包括锌前体（乙酸盐，氯化物，硝酸盐），超声处理条件（振幅，脉冲）和合成后热处理（最高500°C）。由于采用的反应物比例和合成温度，无需热处理即可获得结晶的ZnO样品。在颗粒尺寸和表面积方面，超声处理对形态氧化物特征起主要作用，后者相对于常规合成显示出20倍的增加。有趣的是，1和3 s超声脉冲导致了类似于连续超声的形态特性。在中等温度（400-450°C）下进行的热处理促进了表面羟基化的损失和晶格缺陷的形成，较高的温度不利于样品的形貌。所制备的ZnO用WO3颗粒装饰，并与传统方法使用1 s脉冲的超声辅助技术进行了比较，从而产生了具有增强的可见光吸收的复合材料。测试样品在紫外和可见光下在潮湿空气中对氮氧化物（500-1000 ppb）的光催化降解。通过仔细控制合成程序，相对于商业基准，观察到更好的性能。同样在脉冲超声处理的情况下，来自超声辅助合成的样品显示出比传统参考一致的更好的结果，尤其是对于ZnO-WO3复合材料。超声辅助合成的复合材料显示>