DFT calculation and analysis of the gas sensing mechanism of methoxy propanol on Ag decorated SnO₂ (110) surface

Methoxy propanol has been widely used in modern industry and consumer products. Inhalation or skin exposure to methoxy propanol for a long period would bring about safety challenges on human habitat and health. Ag decorated SnO₂ mesoporous material has been synthesized and shown to exhibit high sensitivity and good selectivity to methoxy propanol among other interferential VOC gases. Density Functional Theory study were conducted to yield insight into the surface-adsorbate interactions and therefore the gas sensing improvement mechanism by presenting accurate energetic and electronic properties for the Ag/SnO₂ system. Firstly, an electron transfer model on Ag and SnO₂ grain interface was put forward to illustrate the methoxy propanol gas sensing mechanism. Then, a three-layer adsorption model (TLAM) was proposed to investigate methoxy propanol gas sensing properties on a SnO₂ (110) surface. In the TLAM method, taking SnO₂ (110) surface for the basis, layer 1 illustrates the decoration of metal Ag on SnO₂ (110) surface. Layer 2 represents the adsorption of molecular oxygen on metal Ag decorated SnO₂ (110) surface. Layer 3 indicates the adsorption of methoxy propanol, and for comparison, three other VOC gases (namely, ethanol, isopropanol and p-xylene) on Ag decorated SnO₂ (110) surface with oxygen species pre-adsorbed consecutively. All the adsorption processes were calculated by means of Density Functional Theory method; the adsorption energy, net charge transfer, DOS, PDOS and also experimental data were utilized to investigate the methoxy propanol gas sensing mechanism on Ag decorated SnO₂ (110) surface with oxygen species pre-adsorbed.