Atomically dispersed rhodium on ordered macroporous In2O3 for the highly sensitive detection of ethanol and the sensing mechanism

Abstract

Ethanol is a volatile organic compound. Exposure to its vapors can cause breathing difficulties, headaches, drowsiness, and eye irritation. The development of highly sensitive ethanol sensors is of great significance in human health monitoring. In this work, 0.14 wt% rhodium on three-dimensionally ordered macroporous (3DOM) In₂O₃ (RhSA–In₂O₃) was synthesized by a UV light reduction method. The sensor based on RhSA–In₂O₃ exhibited high response (4590) to 50 ppm ethanol, high sensitivity (53.01 ppm⁻¹) and an ultra-low detection limit (0.07 ppb). The ac-HAADF-STEM (aberration-corrected high angle annular dark-field scanning transmission electron microscopy), CO-DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy), and XAFS (X-ray absorption fine structure) spectroscopy characterization results indicated that rhodium existed in the atomically dispersed state on In₂O₃, which provided abundant active sites and enhanced the ethanol-sensing response. The sensing mechanism was investigated using an ethanol-DRIFTS technique and an ethanol-acetaldehyde-CO₂ reaction route with low activation energy (84.459 kJ mol⁻¹) was proposed on RhSA–In₂O₃.