Electronic Materials Research Division, Morinomiya Center , Osaka Research Institute of Industrial Science and Technology (ORIST) , Osaka 536-8553 , Japan.
Graduate School of Engineering , Toyohashi University of Technology , Toyohashi , Aichi 441-8580 , Japan.
Inorg Chem. 2018 Nov 5;57(21):13137-13149. doi: 10.1021/acs.inorgchem.8b01242. Epub 2018 Oct 16.
Thermal decomposition of layered zinc hydroxides (LZHs) is a simple and convenient way to achieve porous ZnO nanostructures. The type of anion contained in an LZH determines the fundamental characteristics of the LZH and thus affects the formation process of the resulting porous ZnO. Here we report a comparative study on the crystal orientation relationship between LZH precursors and the corresponding porous ZnO products by using well-faceted and highly oriented LZH crystals with three different anions, i.e., NO, SO, and Cl. Highly oriented LZH crystals were prepared on layer-by-layer coated indium tin oxide substrates by electrodeposition in aqueous solution and were transformed into porous ZnO by calcination in air. The synthesized materials were characterized by X-ray diffraction, scanning electron microscopy with electron backscatter diffraction, Fourier transformed infrared spectroscopy, and X-ray photoelectron spectroscopy. The layered structure of the highly oriented LZHs was parallel to the substrate surface and all transformed to nanoporous ZnO with a ⟨0001⟩ preferred orientation. The ⟨0001⟩ orientation degree and in-plane orientation of the nanoporous ZnO differed significantly depending on the type of anion but not the decomposition temperature, revealing that the initial formation process of ZnO from the LZHs is crucial. Finally, a possible transformation mechanism explaining the difference in the resulting ZnO orientation by anions (NO, SO, and Cl) is discussed on the basis of their layered structure and thermal decomposition processes.
层状锌氢氧化物 (LZH) 的热分解是一种实现多孔 ZnO 纳米结构的简单方便的方法。LZH 中所含阴离子的类型决定了 LZH 的基本特性，从而影响到所得多孔 ZnO 的形成过程。在这里，我们通过使用具有三种不同阴离子（即 NO、SO 和 Cl）的具有良好面和高度取向的 LZH 晶体，对 LZH 前体与相应多孔 ZnO 产物之间的晶体取向关系进行了比较研究。通过在水溶液中的电沉积，在层状涂布的氧化铟锡衬底上制备了高度取向的 LZH 晶体，并通过在空气中煅烧将其转化为多孔 ZnO。通过 X 射线衍射、电子背散射衍射扫描电子显微镜、傅里叶变换红外光谱和 X 射线光电子能谱对合成材料进行了表征。高度取向的 LZH 的层状结构与衬底表面平行，所有结构均转化为具有 ⟨0001⟩择优取向的纳米多孔 ZnO。纳米多孔 ZnO 的 ⟨0001⟩取向度和平面取向因阴离子的类型而有显著差异，但与分解温度无关，这表明 ZnO 从 LZH 初始形成过程至关重要。最后，基于它们的层状结构和热分解过程，讨论了阴离子 (NO、SO 和 Cl) 对所得 ZnO 取向差异的可能转化机制。
