This study investigates the effects of cobalt (Co) substitution in SmFe₁₋ₓCoₓO₃ perovskite oxides on the sensing property of volatile organic compounds (VOCs). The introduction of Co induces a hole-doping effect, increasing electrical conductivity and enabling lower operating temperatures, thereby improving VOC selectivity. SmFe₁₋ₓCoₓO₃ powders were synthesized via the glycothermal method and characterized using X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) surface area measurements. Gas sensing properties were evaluated for ethanol and toluene at varying temperatures and concentrations. The results indicate that Co substitution significantly influences oxidation activity and electrical resistance, thereby modifying gas sensing behavior. The SmFe₁₋ₓCoₓO₃ sensor with x = 0.1 exhibited the highest selectivity of Sethanol/Stouene = 5.89 at 250oC, toward ethanol over toluene, attributed to an optimal balance between electrical conductivity and oxidation activity. Co substitution enhanced the oxidation activities for ethanol and toluene, and the difference in the 50% conversion temperatures (T₅₀) between ethanol and toluene increased with increasing Co content (x). Catalytic activity Additionally, density functional theory (DFT) calculations were performed to gain further insight into the gas sensing mechanism. Surface adsorption energies and electronic interactions of ethanol and toluene on SmFe₁₋ₓCoₓO₃ were analyzed, revealing formation of oxygen vacancy due to the Co-substitution selectively increases the adsorption strength of ethanol. This study highlights the potential of Co-substituted SmFeO₃ as a selective ethanol sensor with lower operating temperatures and enhanced detection capabilities. The findings contribute to the development of advanced perovskite-based gas sensors with improved efficiency and selectivity for real-world applications.
