Microstructure-Controlled Preparation of Monodisperse In2o3 for Excellent Hcho Sensing Properties with High Selectivity and Low Detection Limit

Abstract

Morphology control significantly improves the microstructure, increases the number of defects, tailors porosity, and optimizes the band gap of gas-sensing materials, profoundly affecting the adsorption and desorption capabilities for gas molecules. Herein, we prepared In(OH)3 precursors via a hydrothermal method and rationally controlled the microstructure of In2O3 by varying annealing temperatures (400 °C, 500 °C, 600 °C). The microstructural attributes are anticipated to play a crucial role in dominating the gas-sensing properties of the materials. Characterizations revealed that the porous cubic In2O3-500 (500 °C) exhibited superior properties, including more balanced grain size and crystallinity, superior pore structure, more oxygen vacancies and adsorbed oxygen, and a narrower band gap compared to the surface-dense cubic In2O3-400 (400 °C) and the porous spherical In2O3-600 (600 °C). Gas-sensing tests demonstrated that the three In2O3-based sensors displayed exceptional selectivity towards for formaldehyde (HCHO), with rapid response times (1 s) to 100 ppm HCHO. Notably, In2O3-500 operated at a lower temperature (175 °C), yielded the highest response (200) to 100 ppm HCHO, possessing good humidity resistance, and achieving the lowest detection limit (30 ppb). This study offers insights into the cost-effective and facile fabrication of high-performance HCHO gas sensing materials.

Keywords: In2O3, Hydrothermal method, Microstructure control, Monodisperse, HCHO