Abstract
A diffusion-reaction coupled model was presented to investigate the effects of multiscale pore structure characteristics on gas sensing properties. A series of CoTiO3 powders with different pore size distributions were fabricated by sol-gel method. Experimental results on cobalt titanate thick films show that a well-defined multiscale pore structure is particularly desired for the improvement of sensing performance, instead of just increasing the specific surface area. The theoretical responses of sensing elements with different pore size distributions were derived and compared with experimental data on CoTiO3 sensors exposed to ethanol. The calculated sensitivities considering the influence of pore size changes were also found to be in agreement with the experimental results. A dimensionless Thiele modulus Th was introduced for assessing the critical point corresponding to the transformation from surface reaction-controlled sensitivity into diffusion-controlled sensitivity.
Highlights
Gas sensors based on semiconducting metal oxides have been regarded as the most versatile method for gas detection, due to high sensitivity, good stability, simple fabrication process, and wide variety of applications [1,2,3]
In the presence of target gas, changes in the electrical conductance of the metal oxide materials are caused by the physical adsorption of target gas followed by a chemical reaction between target gas and surface chemisorbed oxygen
Guo et al elucidated that hierarchical porous hollow TiO2 nanofibers exhibited a remarkable higher sensing performance due to the peculiar properties arising from a large surface/volume ratio [15]
Summary
Gas sensors based on semiconducting metal oxides have been regarded as the most versatile method for gas detection, due to high sensitivity, good stability, simple fabrication process, and wide variety of applications [1,2,3]. In the presence of target gas, changes in the electrical conductance of the metal oxide materials are caused by the physical adsorption of target gas followed by a chemical reaction between target gas and surface chemisorbed oxygen. Considerable effort has been directed towards optimizing the structural and textural properties of semiconducting metal oxides [4,5,6,7,8,9,10,11]. Guo et al elucidated that hierarchical porous hollow TiO2 nanofibers exhibited a remarkable higher sensing performance due to the peculiar properties arising from a large surface/volume ratio [15]. Via a graphene oxide-assisted hydrothermal route, Zhao et al reported the design and synthesis of tin oxide hierarchical porous nanosheets, which exhibited greatly enhanced ethanol sensing performance as compared with bare
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