Sensing of n-butanol vapours using an oxygen vacancy-enriched Zn₂SnO₄-SnO₂ hybrid-composite

The precise identification of various toxic gases is important to prevent health and environmental hazards using cost-effective, efficient, metal oxide-based chemiresistive sensing methods. This study explores the sensing properties of a chemiresistive sensor based on a Zn₂SnO₄-SnO₂ microcomposite for detecting n-butanol vapours. The microcomposite, enriched with oxygen vacancies, was thoroughly characterized, confirming its structure, crystallinity, morphology and elemental composition. The sensor demonstrated high repeatability across a temperature range of 275-350 °C and concentrations from 100 to 1000 ppm, with the highest response observed at 350 °C. The concentration-dependent response of the sensor towards n-butanol follows a linear relationship within the studied operating temperature range. The response time increases as the concentration of n-butanol increases. Conductance transients were modelled using the Langmuir-Hinshelwood mechanism, showing temperature-dependent oxidation kinetics. At lower temperatures, the rate-determining step involved n-butanol oxidation, while at higher temperatures, simultaneous oxidation and desorption processes dominated. The calculated activation energy for the n-butanol oxidation step was 0.12 eV. Furthermore, principal component analysis (PCA) effectively discriminated n-butanol from other volatile organic compounds (VOCs), emphasizing the sensor's potential for selective n-butanol detection through a combination of kinetic modelling and statistical analysis.