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TeO 2 , as a promising gas sensor material, has been extensively studied for its capacity to detect hydrogen with high sensitivity. First-principles calculations were applied to explore the adsorption properties of hydrogen (H 2), carbon dioxide (CO 2), methane (CH 4), and hydrogen sulfide (H 2 S) on TeO 2 doped with either Mg or Mn to explore this compound's potential as hydrogen sensors. Hydrogen is more readily adsorbed on pure-TeO 2 , Mg–TeO 2 and Mn–TeO 2 than CO 2 , CH 4 and H 2 S molecules by calculating their adsorption energy and charge transfer; the sequence of adsorption strength is H 2 >H 2 S > CO 2 >CH 4. The hydrogen molecules and pure-TeO 2 , Mg–TeO 2 and Mn–TeO 2 form H–O bonds with lengths of 0.98, 0.98 and 0.99 Å, respectively, indicating that chemical adsorption is dominant between them. The adsorption of hydrogen leads to significant changes in the density of states (DOSs) of pure-TeO 2 , Mg–TeO 2 and Mn–TeO 2 , which may lead to changes in their electrical conductivity. Moreover, the larger diffusion coefficients for hydrogen on the surfaces of pure-TeO 2 , Mg–TeO 2 and Mn–TeO 2 relative to other gases indicates that hydrogen diffuses readily in TeO 2 -based sensing materials, and the higher gas concentration contributes to improvements in response performance. This finding offers a theoretical basis for experimental explorations of the influence of metal dopants on TeO 2 hydrogen sensing performance. [Display omitted] • First-principles methods are performed for metal (Mg, Mn) atoms doped TeO 2 systems. • The TeO 2 systems after doping metal (Mg, Mn) atoms are stable. • Detection of H 2 is related to formation of H–O bonds between H 2 and Mg/Mn–TeO 2. • Mg/Mn doping can greatly improve the gas sensitivity of TeO 2 to hydrogen. [ABSTRACT FROM AUTHOR]

α-phase TeO 2 is a promising sensing material because of its unique ability to detect hydrogen gas. To investigate atomic-level mechanism on gas sensing of TeO 2 , the interaction between H 2 , NH 3 , SO 2 , CO 2 , H 2 S, CH 4 gases and TeO 2 are studied via first principles simulations. By the calculated adsorption energy, radial distribution function, band gap and charge transfer, TeO 2 shows a superior selective detection performance to hydrogen and it is consistent with experimental conclusion. The H–H bond of H 2 break after adsorption and a new H–O bond with length of 0.98 Å forms between TeO 2 and H 2. Moreover, the adsorption of H 2 causes an obvious increasing of DOS near the Fermi level, indicating a clear change in the electric conductivity. The calculated self-diffusion coefficients show that the diffusion of hydrogen molecule in TeO 2 is much easier than the other gases, suggesting a fast response of H 2 by TeO 2. This work provides a theoretical foundation for analysis and design of TeO 2 -based hydrogen sensor. Image 1 • For the first time, atomic sensing mechanism of TeO 2 towards H 2 gas is studied. • Predicted gases sensing behaviours of TeO 2 consist with experiments. • Detection of H 2 is related to formation of O–H bonds between H 2 and TeO 2. • Our analysis provides a basis for designing of TeO 2 -based gas sensor. [ABSTRACT FROM AUTHOR]

As a common toxic gas, the sensing and capture of NO 2 are two important topics closely related to human health and the environment. In this work, the adsorption behavior of a SnS 2 monolayer on gas molecules including NO 2 , CO 2 , SO 2 , NH 3 , acetone, ethanol, methanol and formaldehyde was studied by DFT methods to explore its possibility as a NO 2 gas sensor or capturer. Among these gases, only NO 2 can be chemisorbed on to the SnS 2 monolayer with an adsorption energy of −0.43 eV. Compared with other gases, the significantly altered I–V relationship of the SnS 2 monolayer before and after adsorbing NO 2 demonstrates that the SnS 2 monolayer has superior sensitivity and selectivity for NO 2. In particular, the adsorption of NO 2 by the SnS 2 monolayer strengthens linearly with increasing biaxial strain, while the adsorption of other gases remains weak, thus offering an effective route for the SnS 2 monolayer to capture and release NO 2 by adjusting the magnitude of an applied biaxial strain. These results demonstrate that the SnS 2 monolayer is an excellent candidate material for the effective capture, separation, storage and detection of NO 2. [Display omitted] • NO 2 adsorption properties of SnS 2 monolayer in eight gases were studied by DFT method. • The SnS 2 monolayer shows high gas selectivity and sensitivity to NO 2. • SnS 2 monolayer can realize the application of NO 2 capturer by applying biaxial strain. • The S-vacancy SnS 2 monolayer shows better adsorption sensitivity to NO 2. [ABSTRACT FROM AUTHOR]

• For the first time, atomic-scale gases sensing mechanism of MnPS 3 is studied. • Predicted gases sensing behaviours of MnPS 3 consist with experiments. • Detection of NO 2 is related to formation of P O bond between NO 2 and MnPS 3. • Our work provides an approach for designing MnPS 3 -based gas sensor. Among transition metal thiophosphates (MPX 3), p-type semiconductor MnPS 3 is considered to be a promising sensor material due to high selectivity and sensitivity to NO 2. To explore gas sensing mechanism of MnPS 3 at atomic scale, the electronic properties of NO 2 , NH 3 , H 2 , CO, CO 2 , C 2 H 2 , H 2 S and CH 4 gases in MnPS 3 monolayer are analyzed by density functional theory. The calculated charge transfer, adsorption energy, density of state and band gap change suggest that MnPS 3 exhibits an intense sensing performance to NO 2 than other gases. Upon the adsorption of NO 2 , one of the N O bond in NO 2 breaks and a P O bond forms between NO 2 and MnPS 3. Further, a significant increasing on DOS occurs near Fermi level, suggesting an obvious change in electric conductivity of MnPS 3. The energy barrier and diffusion coefficient shows that the gases are easier to diffuse between adjacent vacancies on the surface of MnPS 3 , and NO 2 is relatively difficult to diffuse than other gases due to chemical adsorption. This work provides a theoretical basis for designing MnPS 3 -based NO 2 sensor. [ABSTRACT FROM AUTHOR]