Pourrahimi Amir Masoud, Liu Dongming, Andersson Richard L, Ström Valter, Gedde Ulf W, Olsson Richard T
Fiber and Polymer Technology, School of Chemical Science and Engineering and ‡Material Science and Engineering, School of Industrial Engineering and Management, KTH Royal Institute of Technology , SE-100 44 Stockholm, Sweden.
Langmuir. 2016 Oct 25;32(42):11002-11013. doi: 10.1021/acs.langmuir.6b03263. Epub 2016 Oct 10.
Controlled aqueous growth of 1 μm flower-shaped ZnO particles with a hierarchical subset of exposed nanosheets represented by {21̅0} crystal faces, followed by annealing at temperatures up to 1000 °C, is presented. The flower-shaped particles showed superior photocatalytic performance compared to the crystal faces of 20 nm ZnO nanoparticles. The photocatalytic reaction rate of the flower-shaped particles before annealing was 2.4 times higher per m compared with that of the nanoparticles with double specific surface area. Crystal surface defects and nanosized pores within the flower-shaped particles were revealed by porosity measurements and electron microscopy. A heat treatment at 400 °C was found to be optimal for removal of nanoporosity/surface defects and impurities while retaining the hierarchical superstructure. The heat treatment resulted in a photodegradation efficiency that increased by an additional 43%, although the specific surface area decreased from 16.7 to 13.0 mg. The enhanced photocatalytic effect remained intact under both acidic and alkaline environments owing to the {21̅0} crystal surfaces, which were less prone to dissolution than the nanoparticles. The photocatalytic performance relied on primarily three factors: the removal of surface impurities, the oxygen termination of the {21̅0} crystal faces, and the promotion of charge carrier lifetime by removal of lattice defects acting as recombination centers. The synthesis presented is an entirely hydrocarbon- and surfactant-free ("green") preparation scheme, and the formation of the flower-shaped particles was favored solely by optimization of the reaction temperature after the correct nitrate salt precursor concentrations had been established.
本文介绍了通过控制水相生长制备出具有由{21̅0}晶面表征的纳米片分级子集的1μm花状ZnO颗粒，随后在高达1000°C的温度下进行退火处理。与20nm ZnO纳米颗粒的晶面相比，花状颗粒表现出优异的光催化性能。退火前花状颗粒的光催化反应速率每平方米比具有两倍比表面积的纳米颗粒高2.4倍。通过孔隙率测量和电子显微镜揭示了花状颗粒内的晶体表面缺陷和纳米级孔隙。发现400°C的热处理对于去除纳米孔隙率/表面缺陷和杂质同时保留分级超结构是最佳的。尽管比表面积从16.7降至13.0mg，但热处理导致光降解效率额外提高了43%。由于{21̅0}晶体表面在酸性和碱性环境下都不易溶解，因此增强的光催化效果得以保持。光催化性能主要依赖于三个因素：表面杂质的去除、{21̅0}晶面的氧端基化以及通过去除作为复合中心的晶格缺陷来延长电荷载流子寿命。所介绍的合成方法是一种完全无烃和无表面活性剂的（“绿色”）制备方案，并且在确定了正确的硝酸盐前体浓度后，仅通过优化反应温度就有利于花状颗粒的形成。
