Department of Chemistry, Università degli Studi di Milano, Italy; Consorzio INSTM, Florence, Italy.
Department of Chemistry, Università degli Studi di Milano, Italy.
Ultrason Sonochem. 2020 Sep;66:105119. doi: 10.1016/j.ultsonch.2020.105119. Epub 2020 Mar 31.
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 WO 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-WO composites. The composite by ultrasound-assisted synthesis showed > 95% degradation in 180 min and doubled NO degradation under visible light with respect to the conventional composite.
采用超声辅助技术合成 ZnO 光催化剂。研究了几种实验参数，包括锌前体（醋酸盐、氯化物、硝酸盐）、超声条件（幅度、脉冲）和后合成热处理（高达 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 ZnO 样品。超声在颗粒尺寸和表面积方面对氧化物形态特征起着重要作用，后者比传统合成方法提高了 20 倍。有趣的是，1 和 3 s 的超声脉冲导致形态特性类似于连续超声。在中等温度（400-450°C）下进行热处理会促进表面羟基化的损失和晶格缺陷的形成，而较高的温度对样品形态不利。通过比较使用 1 s 脉冲的超声辅助技术与传统方法，将 WO 颗粒修饰到制备的 ZnO 上，形成了具有促进可见光吸收的复合材料。在 UV 和可见光下，在加湿空气中对氮氧化物（500-1000 ppb）进行光催化降解测试。通过仔细控制合成程序，与商业基准相比，观察到更好的性能。与传统参考相比，超声辅助合成的样品（包括脉冲超声的情况）始终表现出更好的结果，特别是对于 ZnO-WO 复合材料。与传统复合材料相比，超声辅助合成的复合材料在 180 分钟内显示出超过 95%的降解，并且在可见光下将 NO 降解提高了一倍。
