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

Abstract

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.