The Role of NiO Doping in Reducing the Impact of Humidity on the Performance of SnO₂‐Based Gas Sensors: Synthesis Strategies, and Phenomenological and Spectroscopic Studies

Abstract

The humidity dependence of the gas‐sensing characteristics in SnO2‐based sensors, one of the greatest obstacles in gas‐sensor applications, is reduced to a negligible level by NiO doping. In a dry atmosphere, undoped hierarchical SnO2 nanostructures prepared by the self‐assembly of crystalline nanosheets show a high CO response and a rapid response speed. However, the gas response, response/recovery speeds, and resistance in air are deteriorated or changed significantly in a humid atmosphere. When hierarchical SnO2 nanostructures are doped with 0.64–1.27 wt% NiO, all of the gas‐sensing characteristics remain similar, even after changing the atmosphere from a dry to wet one. According to diffuse‐reflectance Fourier transform IR measurements, it is found that the most of the water‐driven species are predominantly absorbed not by the SnO2 but by the NiO, and thus the electrochemical interaction between the humidity and the SnO2 sensor surface is totally blocked. NiO‐doped hierarchical SnO2 sensors exhibit an exceptionally fast response speed (1.6 s), a fast recovery speed (2.8 s) and a superior gas response (Ra/Rg = 2.8 at 50 ppm CO (Ra: resistance in air, Rg: resistance in gas)) even in a 25% r.h. atmosphere. The doping of hierarchical SnO2 nanostructures with NiO is a very‐promising approach to reduce the dependence of the gas‐sensing characteristics on humidity without sacrificing the high gas response, the ultrafast response and the ultrafast recovery.

Microwave gas sensing with a microstrip interDigital capacitor: Detection of NH3 with TiO2 nanoparticles

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Facile synthesis of mesoporous hierarchical Co3O4–TiO2 p–n heterojunctions with greatly enhanced gas sensing performance

“…Therefore, there is a need to develop high-performance gas sensors with high sensitivity, low operating temperature and good stability for real-time monitoring of toluene and xylene. A variety of metal oxide semiconductors have been used as sensing materials to detect VOCs, such as ZnO, [4][5][6] SnO2, [7][8][9] In2O3, [10][11][12] Co3O4, [13][14][15] TiO2, 16,17 WO3, [18][19][20][21] Fe2O3, [22][23][24] Cu2O/CuO, 25,26 and NiO. 27 Among these metal oxide semiconductors, Co3O4 is believed to be a promising candidate for sensing of toluene and xylene because of its excellent catalytic activity for oxidizing them at low temperature which results from its larger adsorption amount of oxygen 28 on the surface than others and multivalent properties facilitating redox reactions.…”

Trimodally porous SnO2 nanospheres with three-dimensional interconnectivity and size tunability: a one-pot synthetic route and potential application as an extremely sensitive ethanol detector

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