Augmented hydrogen adsorption on metal (Mg, Mn) doped α-phase TeO2: A DFT investigation

Abstract

TeO2, 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 (H2), carbon dioxide (CO2), methane (CH4), and hydrogen sulfide (H2S) on TeO2 doped with either Mg or Mn to explore this compound's potential as hydrogen sensors. Hydrogen is more readily adsorbed on pure-TeO2, Mg–TeO2 and Mn–TeO2 than CO2, CH4 and H2S molecules by calculating their adsorption energy and charge transfer; the sequence of adsorption strength is H2>H2S > CO2>CH4. The hydrogen molecules and pure-TeO2, Mg–TeO2 and Mn–TeO2 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-TeO2, Mg–TeO2 and Mn–TeO2, which may lead to changes in their electrical conductivity. Moreover, the larger diffusion coefficients for hydrogen on the surfaces of pure-TeO2, Mg–TeO2 and Mn–TeO2 relative to other gases indicates that hydrogen diffuses readily in TeO2-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 TeO2 hydrogen sensing performance.