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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]

[Display omitted] • For the first time, atomic sensing mechanism of γ-CoV 2 O 6 -PdO and γ-CoV 2 O 6 towards H 2 gas is studied. • Predicted gases sensing behaviors of γ-CoV 2 O 6 -PdO as well as γ-CoV 2 O 6 consist with experiments results in other work. • Detection of H2 is related to formation of O–H bonds between H2 and O atom in γ-CoV 2 O 6. • Our analysis provides a basis for designing of γ-CoV 2 O 6 -based gas sensor. The incorporation of PdO is an effective way to enhance the sensitivity of γ-CoV 2 O 6 gas sensors, while the interaction mechanism between gas and γ-CoV 2 O 6 -PdO even γ-CoV 2 O 6 systems are still not clear. In this study, the interaction work between H 2 , NO, H 2 S, acetone and γ-CoV 2 O 6 as well as γ-CoV 2 O 6 -PdO are investigated systematically through density functional theory (DFT) as well as molecular dynamics simulations. According to the obtained adsorption energy, band gap and charge transfers, γ-CoV 2 O 6 and γ-CoV 2 O 6 -PdO exhibits much superior sensitivity towards H 2 gas than other three gases. The mechanism of sensing behavior of H 2 on γ-CoV 2 O 6 is the elongated H-H bond in H 2 and forms a bond with an oxygen atom on the substrate to form H-O-H molecule group. In addition, the adsorption of H 2 on γ-CoV 2 O 6 causes a peak near the Fermi level, and the band gap reduces as well, therefore, the conductivity of γ-CoV 2 O 6 is changed and makes the sensing feasible. For H 2 adsorption, the band gap change rates are 93.8% and 70.8%, which are much higher than other gas molecules. The further comparative research on gases diffusion characteristics indicates that both γ-CoV 2 O 6 and γ-CoV 2 O 6 -PdO H 2 has fast response toward H 2 molecules. Our results present γ-CoV 2 O 6 system can detect H 2 effectively, and when it was decorated by PdO, the sensing behavior of γ-CoV 2 O 6 toward H 2 is improved, indicating it is a promising sensing material of H 2 gas. [ABSTRACT FROM AUTHOR]