One-step synthesis of hierarchical α-Ni(OH)2 flowerlike architectures and their gas sensing properties for NOx at room temperature†
Abstract
In this paper, three-dimensional (3D) flowerlike α-Ni(OH)2 nanocrystals with hierarchical architectures were prepared through a one-step method. It was found that the 3D hierarchical nanostructures are actually composed of thin nanosheets or nanopetals, which consist of many ultrafine nanoparticles with 3–5 nm diameters. The growth mechanism for the hierarchical flowerlike nanocrystals is described as the process of nucleation, growth, stacking and self-assembly. The gas sensing properties of α-Ni(OH)2 nanocrystals for NOx gas was investigated at room temperature and the sensing mechanism was discussed as two aspects: 1) relation between the porosity and diffusion, adsorption/desorption of the gas on the surface of the α-Ni(OH)2 nanocrystals; 2) the effect of the chemical composition of the layered double hydroxide-like (LDHs-like) structure on the ability of proton transportation between adjacent NiOH layers and between overlapped ultrafine nanocrystals. The results demonstrate that the α-Ni(OH)2 structures, synthesized by refluxing 0.07 mol L−1 Ni(NO3)2·2H2O, not only presents excellent gas-sensing properties but also has good repeatability and a longer service life. These α-Ni(OH)2 nanocrystals with 3D hierarchical structures and a unique chemical composition have significant implications for the practical application of gas sensors.
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