Enhanced gas sensing performances of hydrogenated MnO octahedrons with {111} facets and the sensing mechanism of unsaturated Mn as a reactive atom

• Published in: Journal of alloys and compounds 2021-12, Vol.884, p.160872, Article 160872
• Main Authors: Xiang, Rong, Zhang, Le, Guo, Junyi, Wang, Ye, Yuan, Yukun, Wang, Yingfei, Chen, Mengdi, Qi, Chen, Liu, Bin, Zhao, Hua, Yang, Heqing
• Format: Article
• Language: English
• Subjects: Chemical reactions; Ethanol; Gas sensing mechanism; Gas sensors; Manganese oxides; MnO octahedron; Octahedrons; Selective adsorption; Sensing active surface; Sensing reactive atoms; Triethylamine; Unsaturated Mn atom; {111} crystal facets
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.160872

•Sensitivity of {111} faced MnO octahedron is signally increased by hydrogenation.•This results from an increase in the density of unsaturated Mn atoms on the surface.•The unsaturated Mn atoms are evidenced to serve as an active site for gas sensing.•They can absorb oxygen, generate free electrons and catalyze the sensing reaction. MnO octahedrons with exposed {111} crystal faces have been synthesized in a solvothermal system of Mn(Ac)2 and C2H5OH at 200 °C for 48 h. Formation of the MnO octahedron results from the selective adsorption of -OCH2CH3 and -OH groups on the (111) crystal plane. Responses of the MnO octahedrons towards acetone, triethylamine, ethanol and n-Butylamine are enhanced by increasing numbers of the unsaturated 2, 3 and 5-coordinated Mn atoms on the (111) surface by removing surface C2H5O- and -OH groups through hydrogenation. Thus, the exposed Mn-MnO (111) face is found to be a gas sensing active surface, the unsaturated 2, 3 and 5-coordinated Mn atoms on the (111) surface are evidenced to be the sensing reactive atoms and a detailed sensing mechanism is presented. The unsaturated active Mn atoms produce electrons, adsorb oxygen and catalyze the sensing reactions. The mechanism can deepen the understanding of the nature of oxide semiconductor gas sensing and is helpful to the design of high performance gas sensing materials.