Gadolinium-Doped CeO2 Gas Sensor for H2S Sensing

Abstract

Dihydrogen sulfide (H2S) gas has a flammable nature and is one of the most toxic and dangerous gases. Even small concentrations can be fatal to humans. Herein, we investigated the H2S gas-sensing features of commercial pristine cerium oxide (CeO2 ) and gadolinium (Gd)-doped CeO2 (GDC) nanoparticles. First, the sensing materials were well-characterized using various methods including X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction to gain insight into their chemical composition, morphology, phases, and crystallinity, respectively. In the next step, gas sensors were fabricated using a top electrode (Au/Ti) configuration. Preliminary H2S-gas-sensing studies revealed that GDC gas sensor had a superior gas response to H2S gas than the pristine CeO2 gas sensor at 350°C. The responses of the pristine CeO2 gas sensor to 20 ppm H2S gas was 1.542, while the response of the GDC gas sensor to the aforementioned H2S concentration was 3.489. In addition, the GDC sensor exhibited good selectivity to H2S gas among C2H5OH, C7H8 and NH3 gases. Also, we investigated the response of the sensor in up to 60% relative humidity. The enhanced response of the GDC gas sensor to H2S gas was mainly related to the formation of oxygen defects as a result of Gd-doping in CeO2 . Also, good selectivity to H2S was related to the sensing temperature, the higher reactivity of H2S relative to other gases and the small bond energy of H-SH. This study demonstrates the promising ability of Gd-doping to enhance the H2S gas-sensing characteristics of CeO2 , which can be applied to other similar systems based on semiconducting metal oxides.