Efficient H2 gas sensor based on 2D SnO2 disks: Experimental and theoretical studies

Abstract

2D SnO2 disks with excellent purity and crystallinity were synthesized through a low cost, facile hydrothermal process and were characterized in terms of their morphological, structural, optical and electrochemical properties. The 2D disk-like morphology of synthesized SnO2 presented the average thickness of ∼1 μm and possessed the typical rutile tetragonal phase for the SnO2 with preferred growth along (100) plane. As-synthesized SnO2 disks were used for the fabrication of gas sensors for reducing gases like H2, CO, and C3H8. With the optimized temperature at 400 °C, the as-synthesized SnO2 electrode expressed the gas responses of 14.7, 9.3 and 8.1 for H2, CO, and C3H8, respectively. Contrary, the reasonable response times of 4 s, 3 s, and 8 s and the recovery times of 331 s, 201 s, and 252 s were recorded for H2, CO, and C3H8 gases, respectively. The DFT studies conducted herein suggest that the adsorbed oxygenated species act as a primary redox mediator for gas sensing reaction between reductive gases like H2, CO and C3H8, and SnO2 sensor. From DFT analysis, a very low heat of adsorption (≤0.2 eV) estimated which suggested the physisorption of the H2 molecules on the surface of the sensing material (i.e. SnO2). In contrast, the deposited oxygen atom forms strong chemical bonds with O2c and O3c sites. The oxygen atom bonded to O2c site control the conductivity of the sensor better than the O3c sites.