State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , Shaanxi , China.
Department of Physics and Department of Materials Science and Engineering , City University of Hong Kong , Tat Chee Avenue , Kowloon 999077 , Hong Kong, China.
ACS Appl Mater Interfaces. 2019 Apr 3;11(13):12958-12967. doi: 10.1021/acsami.8b22533. Epub 2019 Mar 21.
Although high-energy facets on metal oxides are usually active and preferred for gas sensing, it is difficult to expose them according to thermodynamics. In this work, nanocomposites of SnO and graphene are prepared by a hydrothermal method. The SnO nanoparticles change from a lance shape to an octahedral shape as the concentration of HCl in the solution is increased gradually from 6.5 to 10 vol %. However, the SnO nanoparticles have an elongated octahedral shape if the concentration of HCl is increased further. The octahedral SnO nanoparticles are mainly surrounded by high-surface-energy {221} facets, thus facilitating gas sensing. First-principles calculation shows that the surface energy and adsorption energy of the {221} facets are larger than those of the stable {110} facets, and so, the gas adsorption capacity on the {221} facets is better. Furthermore, because the Fermi level of the SnO{221} facet is higher than that of graphene, the electrons are transferred from SnO nanoparticles to graphene sheets, enabling effective electron exchange between the composite and external NO gas. The excellent gas-sensing properties of the octahedral SnO/graphene composites are ascribed to the high-surface-energy {221} facets exposed.
虽然金属氧化物的高能面通常是活性的，并且优先用于气体传感，但根据热力学很难暴露它们。在这项工作中，通过水热法制备了 SnO 和石墨烯的纳米复合材料。随着溶液中 HCl 浓度从 6.5 增加到 10 体积%，SnO 纳米颗粒逐渐从 lance 形状变为八面体形状。然而，如果 HCl 浓度进一步增加，SnO 纳米颗粒则具有拉长的八面体形状。八面体 SnO 纳米颗粒主要由高表面能的{221}面包围，从而有利于气体传感。第一性原理计算表明，{221}面的表面能和吸附能大于稳定的{110}面，因此，{221}面的气体吸附能力更好。此外，由于 SnO{221}面的费米能级高于石墨烯，电子从 SnO 纳米颗粒转移到石墨烯片上，使复合材料与外部 NO 气体之间能够有效地进行电子交换。暴露的高表面能{221}面赋予了八面体 SnO/石墨烯复合材料优异的气体传感性能。
