Synthesis and gas-sensing properties of nano- and meso-porous MoO3-doped SnO2

Abstract

Nano-and meso-porous SnO 2 powders doped with and without 1~10 wt% MoO 3 have been synthesized by an ultrasonic spray-pyrolysis method employing a precursor aqueous solution containing tin (IV) chloride pantahydrate (SnCl 4 ·5H 2 O), ammonium heptamolybdate and polymethylmethacrylate (PMMA) microspheres as a template, and the effects of MoO 3 -doping and the addition of PMMA microspheres on the structural, morphological and gas-sensing properties of SnO 2 were investigated in this study. It is confirmed that control of the amounts of PMMA microspheres in the precursor solution was effective in realizing well-developed nano-and meso-porous structures of SnO 2 by X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and the measurement of specific surface area and pore size distribution using a N 2 adsorption isotherm. Gas-sensing properties of their thick films (about 50 µm thick), which were fabricated by screen-printing to various gases (NO 2 , C 2 H 5 OH and H 2 ) were tested in ambient air. The doped thick films showed a high response and selectivity to 5 ppm NO 2 gas in the case of 10 wt% MoO 3 -doping in both nano-and meso-porous structures of SnO 2 . We observed that the presence of Mo species in SnO 2 lattice can improve the sensor response and selectivity towards NO 2 gas. The effect of the MoO 3 -doping on the sensing characteristics of these films towards NO 2 was discussed.

Highly active Pt catalysts promoted by molybdenum-doped SnO2 for methanol electrooxidation

“…3Fshows the Mo3d XPS spectra of the representative Pte(MoO 3 ) 2.0 SnO 2 /C sample. The well-symmetrical Mo3d3/2 and Mo3d5/2 spectra were located at 236.4 and 233.3 eV, which correspond to the signals of Mo(VI)[27]. For the other Pte(MoO 3 ) m SnO 2 /C samples, similar profile and position of the Mo3d spectra were also found (not shown here).…”

Improvement in NO2 Sensing Properties of Semiconductor-Type Gas Sensors by Loading of Au Into Porous In2O3 Powders

“…Therefore, many researchers have reported the enhanced sensing performances by the structural modification of the sensing layer with rod-like (Wei et al, 2014;Takacs et al, 2015), plate-like (Chen et al, 2014;Guo, 2016), flower-like (Wang et al, 2014(Wang et al, , 2015, or urchin-like structured oxide (Tang et al, 2013). Our group has also studied the introduction of ordered porous structures into metal-oxide layers of semiconductor-type gas sensors to enhance their gas diffusivity and surface area during the last 20 years (Hyodo et al, 2001(Hyodo et al, , 2002(Hyodo et al, , 2003(Hyodo et al, , 2005(Hyodo et al, , 2010(Hyodo et al, , 2013(Hyodo et al, , 2017Hashimoto et al, 2008;Hieda et al, 2008;Firooz et al, 2010). For example, we synthesized mesoporous SnO 2 powders by utilizing the self-assembly of surfactants with a size of several nanometers, and their sensors showed the quite large H 2 response due to an increase in the specific surface area (Hyodo et al, 2001(Hyodo et al, , 2002(Hyodo et al, , 2003.…”

Synthesis of SnO2–ZnO heterostructured nanofibers for enhanced ethanol gas-sensing performance

“…In order to improve their properties, many efforts have been focused on the modification of semiconduction gas sensors by doping with elements or metal oxides such as Pd-doped SnO 2 , Ni-doped ZnO, Ce-doped SnO 2 , SnO 2 doped In 2 O 3 and ZnO doped SnO 2 [7][8][9][10][11]. The addition of a second component as a surface modifier was used both as active sites for redox processes and as promoting free charge carriers that increase the electronic conductance of the oxide films [12]. As two important kinds of fundamental materials, SnO 2 and ZnO have been widely studied due to their range of conductance variability and their response toward different gases [13].…”