The effects of Co doping on the gas sensing performance of In2O3 porous nanospheres

Gas sensor constructed with metal oxide semiconductor (MOS) has attracted a growing concern owing to its feasibility for rapid detection of various harmful and pollutant gases. However, the sensors made of pure MOS usually suffer from the drawbacks of high working temperature, low sensitivity and poor selectivity. Herein, we propose a Co-doping strategy to upgrade the gas sensing performance of In2O3. To expound it, Co-doped In2O3 porous nanospheres (Co-In2O3 PNSs) with the diameter of ∼120 nm was prepared from home-made In(OH)3 NSs via a soaking-lyophilization-calcination method and their sensitive performance towards several volatile organic compounds (VOCs) was investigated in detail. Compared to pure In2O3 sensor, the best Co-In2O3 sensor (with optimized 0.5 mol% Co) exhibited outstanding improvements in triethylamine (TEA) sensing performance, especially including lower optimal working temperature (OWT: 220 °C vs 320 °C), higher response (Ra/Rg: 3500 vs 60 for 10 ppm TEA), and better selectivity (selectivity coefficient STEA/Sethanol: 400 vs 1850). Besides, an interesting selectivity transformation from ethanol to formaldehyde was also observed after Co doping. These improvements of Co-In2O3 PNSs were mainly attributed to their reduced crystallite size, increased oxygen vacancy concentration, narrowed bandgap, as well as upshifted Fermi level, whose mechanism was discussed.