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In this paper, we adopted the first-principles calculations to investigate the sensing properties of the GeP monolayer to four SF6 decomposition gas molecules (H2S, SO2, SO2F2 and SOF2). By discussing the calculated adsorption energy, charge transfer, work function variation combined with charge density difference and electron localization function analysis, we find that GeP monolayer exhibits favorable adsorption strength to SO2 molecule with the most intense charge interaction. And SO2 adsorption can remarkably change the density of states (DOS) of GeP monolayer. Furthermore, we also study the adsorption performance of SO2 molecule on GeP monolayer under applied biaxial strain and external electric field. And the results demonstrate that applying negative electric field can significantly enhance the sensitivity of GeP monolayer to SO2. Therefore, GeP monolayer is a potential candidate for highly sensitive and selective tunable SF6 decomposition gas sensor for on-line diagnostics of power equipment. [ABSTRACT FROM AUTHOR]

• High selectivity and sensitivity of GeP monolayer to nitrogen oxides. • The variation of work function change can be used to distinguish NO 2 and NO. • Compressive strain improve sensitivity of GeP to NO 2 without raising recovery time. • Applied negative electric field can greatly enhance response of GeP monolayer to NO 2. The sensing properties of GeP monolayer to small gas molecule (CO, CO 2 , O 2 , H 2 O, NH 3 , NO and NO 2) have been investigated by performing first-principle calculations. Based on calculated adsorption distance, adsorption energy and charge transfer, we find that GeP monolayer is the most sensitive to NO 2 and NO molecules, and all gas molecules act as acceptors to gain electrons from GeP monolayer. The adsorption energy of NO 2 is smaller than that of NO molecule, which implies that NO 2 is more easily desorbed from GeP. And different work function changes also indicate the possibility to identify NO 2 and NO in an oxygen-free environment. Moreover, we apply uniaxial and biaxial strains to GeP monolayer and find that a small biaxial compressive strain can effectively enhance the sensitivity of work function type sensor based GeP to NO 2 molecule without increasing recovery time. We also discuss the effect of external vertical electric field on the adsorption performance of NO 2 molecule. The negative electric field can significantly increase the adsorption strength, charge transfer and work function change of NO 2 -GeP system. Our results indicate that GeP monolayer is a potential candidate for NO 2 gas sensor. [ABSTRACT FROM AUTHOR]

• Adsorption properties of SF6 decomposition components on ceria surface were compared based on DFT calculations. • Adsorption of H 2 S, SO 2 and SOF 2 cause conspicuous charge redistribution on CeO 2 (110) surface. • CeO 2 (110) shows higher sensitivity to H 2 S, SO 2 and SOF 2 in comparison with SF 6. The detection of sulfur hexafluoride (SF 6) decomposition components is significant for monitoring the conditions of SF 6 -gas-insulated equipment. In present study, the adsorption of SF 6 and its decomposition components (H 2 S, SO 2 , SOF 2 , and SO 2 F 2) on ceria (110) was investigated by performing calculations based on density functional theory (DFT). Adsorption energy, adsorption configuration, charge transfer, density of states, potential energy and work function for molecular adsorption were adopted to evaluate the performance of ceria (110) on sensing SF 6 decomposition components. Among all the gas molecules, H 2 S, SO 2 and SOF 2 were chemically adsorbed on ceria surface with the adsorption energy following the order: SOF 2 > SO 2 > H 2 S, while SO 2 F 2 and SF 6 were physically adsorbed on the substrate. Besides, the amount of charge transfer and work function modification of H 2 S, SO 2 and SOF 2 molecule's adsorption were larger than those of SO 2 F 2 and SF 6. These calculation results demonstrated ceria (110) showed prominent sensitivity to H 2 S, SO 2 and SOF 2 while less activity to SF 6 , which means sensor based on ceria is promising for detecting H 2 S, SO 2 and SOF 2 in SF 6 gas background, and thus has the potential to online monitor the working condition of SF 6 -gas-insulated equipment. [ABSTRACT FROM AUTHOR]