Vapor-phase modulated sphere-like In2O3@N-C complexes for improving gas sensitivity

Abstract

Sensitivity is a challenging issue for most gas sensors in detecting volatile organic compounds (VOCs). In this study, an alternative ethanol chemosensor based on In2O3@N-C nanospheres (NSs) was synthesized successfully through a simple vapor-phase method. The In2O3@N-C NSs structure, morphology and chemical states were characterized by XRD, SEM, TEM (HRTEM), XPS, and PL measurements. The gas sensor based on In2O3@N-C NSs showed high sensitivity for a wide range of ethanol concentrations (0.5–200 ppm). The N-C shell increased the concentration of oxygen vacancies, thereby increasing the number of active sites as verified by XPS and PL. We investigated the effect of the N–C shell on gas sensitivity. Compared with the pure In2O3 sensor, the In2O3@N-C NS sensor exhibited significantly enhanced sensing performance toward ethanol with a response to 100 ppm ethanol was approximately 145, at least seven times higher than the other gases and two times higher than the pure In2O3 NS sensor (83). As the relative humidity increased, the sensor sensitivity decreased. However, even under a high humidity environment of 70%, the response of the In2O3@N-C NS sensor was still above 20. Our results indicated that In2O3@N-C NSs are prospective candidates for ethanol gas sensor fabrication.