Chemiresistive Gas Sensors Based on Highly Permeable Sn-Doped Bismuth Subcarbonate Microspheres: Facile Synthesis,Sensing Performance,and Mechanism Study

Acetic acid (CH₃COOH) detection with high selectivity at low temperatures is significant due to its wide applications in the chemical, medical, and catering industries. Chemiresistive gas sensors based on metal oxide semiconductors (MOSs) are widely used in detecting various gases, but it is necessary to develop MOSs with novel nanostructures to enhance gas-sensing performance. Herein, a series of bismuth subcarbonate (Bi₂O₂CO₃, abbreviated as BCO) microspheres with highly permeable lamellar structure and tunable Sn-doping ratios (0–5 at%) is synthesized by controlling kinetics equilibrium of the hydrothermal reaction. The sensor based on 3 at% Sn-doped BCO microspheres exhibits excellent gas-sensing performances toward acetic acid (10 ppm), including high sensitivity (S = 8.3), fast recovery speed (10 s), long-term stability (over 30 days), and good selectivity at a low temperature (150 °C). The unique permeable lamellar structure assembled from 2D Sn-doped BCO nanosheets and rich Sn⁴⁺ doping-induced active sites is mainly responsible for the enhanced gas-sensing performances. Moreover, a new acetic acid reaction process is revealed via in situ diffuse reflectance infrared transform spectroscopy. Density functional theory calculations indicate that Sn-doped BCO has a higher acetic acid adsorption energy and a larger charge transfer than pristine BCO.