Antimony Doping in SnO₂ Nanoparticles for Sensitive NO₂ Sensors

Abstract

Developing cost-effective NO 2 sensors with ppb-level limit of detection (LOD) is crucial for effectively monitoring this widespread toxic gas. SnO 2, a promising candidate, suffers from limitations including poor selectivity, high operating temperature, and sensitivity to moisture. To address these challenges, we synthesized high-performance Sb-doped SnO 2 sensors via a hydrothermal method. All SnO 2 products exhibit rutile tetragonal crystalline structures and consist of fine nanoparticles, primarily in the several-nanometer range. It is found that dopant activation in the SnO 2 lattice is dependent on both temperature and doping concentration with minimum resistivity achieved at optimal annealing temperature. For sensor fabrication, an annealing condition at 300 °C in ambient air for 2 h was chosen. All sensors demonstrated prominent selectivity toward NO 2 . The sensor response follows a volcano-shaped curve, with the 1.0 and 2.0 atom % Sb-doped sensors exhibiting the highest responses at room temperature (∼25 °C). This peak response shifts to the 0.1 and 1.0 atom % Sb-doped sensors at 75 °C. The optimal operating temperature for achieving the highest response progressively decreases with increasing Sb doping, while moisture resistance also improves. The SnO 2:0.1%Sb sensor demonstrates the most impressive overall performance, exhibiting a higher response stability against temperature variation. It boasts an ultrahigh response of 2.65 × 10 4, rapid response/recovery times of 153 s/11 s to 1 ppm of NO 2 at 75 °C, and a LOD down to 20 ppb. Density functional theory calculations suggest that moderate Sb doping level leads to stronger NO 2 adsorption, explaining the observed optimal performance at moderate doping concentrations.

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