Abstract
Reversible H2 gas sensing at room temperature has been highly desirable given the booming of the Internet of Things (IoT), zero-emission vehicles, and fuel cell technologies. Conventional metal oxide-based semiconducting gas sensors have been considered as suitable candidates given their low-cost, high sensitivity, and long stability. However, the dominant sensing mechanism is based on the chemisorption of gas molecules which requires elevated temperatures to activate the catalytic reaction of target gas molecules with chemisorbed O, leaving the drawbacks of high-power consumption and poor selectivity. In this work, we introduce an alternative candidate of cobalt oxysulfide derived from the calcination of self-assembled cobalt sulfide micro-cages. It is found that the majority of S atoms are replaced by O in cobalt oxysulfide, transforming the crystal structure to tetragonal coordination and slightly expanding the optical bandgap energy. The H2 gas sensing performances of cobalt oxysulfide are fully reversible at room temperature, demonstrating peculiar p-type gas responses with a magnitude of 15% for 1% H2 and a high degree of selectivity over CH4, NO2, and CO2. Such excellent performances are possibly ascribed to the physisorption dominating the gas–matter interaction. This work demonstrates the great potentials of transition metal oxysulfide compounds for room-temperature fully reversible gas sensing.
Highlights
Gas sensors have been an effective tool in monitoring gaseous pollutants, industrial production and household safety, greenhouse gas emission, and human health [1,2,3]
According to the scanning electron microscope (SEM) images shown in Figure 1a and the inset, initial cobalt sulfide (CoS) exhibited a micro-cage morphology self-assembled by the hexagonal sheets
Both the transmission electron microscopy (TEM)-energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) results revealed that the majority of S atoms within the Co-S framework were replaced by O atoms, causing the crystal transformation from initially hexagonal to tetragonal coordination
Summary
Gas sensors have been an effective tool in monitoring gaseous pollutants, industrial production and household safety, greenhouse gas emission, and human health [1,2,3]. Metal oxides (e.g., SnO [7,8,9,10,11,12], ZnO [13,14,15,16,17,18], WO3 [19,20,21,22,23,24], TiO2 [12,14,25,26] etc.) have been the most studied category of core-sensitive materials in semiconducting gas sensors Their gas sensing performances are normally observed at elevated temperatures which allow for sufficient energy for the interaction of surface-adsorbed O with the target gas molecules [7,10,11,15,16,18,19,21,22,26]. The exploration of alternative semiconducting candidates has been an ongoing request
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