Although chemiresistive gas sensors, based on metal-oxide semiconductors, have exhibited particular promise for the monitoring of air pollution, they are often limited because of poor selectivity. In that case, to overcome this issue, according to the essence of the gas-sensing process, the method of reforming the surface reaction path on the surface of the sensing materials was used. Here, we report that Pd nanoparticles supported over the In2O3 composites, featured with a yolk-shell structure, enable the trace detection of carbon disulfide (CS2) gas molecules, which are immensely dangerous to humans and animals. Moreover, the prominent enhancement of the gas response and the ultraselective CS2-sensing characteristic were acquired in comparison with pristine In2O3 sensors. Significantly, density functional theory calculations revealed that the Pd supported on In2O3 greatly facilitates the adsorption capacity to CS2, and the intermediate S, produced by Pd-catalyzed desulfurization reaction, on the Pd/In2O3 surface during the sensing process is a key to achieving a high CS2 gas response as well as ultraselectivity, which is well in agreement with the X-ray photoelectron spectroscopy analysis results. On the basis of these results, a new sensing mechanism model for the CS2-sensing process was put forward.
Keywords: Pd/In2O3 composite; carbon disulfide; density functional theory; intermediate S; ultraselectivity.