VOCs gas sensing properties on SnO2 (110) surface with dissociated oxygen species pre-adsorbed: experiments and DFT analysis

Abstract

SnO2 nanoparticle material was synthesized and used to fabricate MHP based gas sensor, which showed better gas sensing performance to ethanol than the other target gases. DFT calculation and analysis for the gas adsorption properties on SnO2(110) surface were conducted thoroughly by mean of DMol3 package in Materials Studio software to yield insight into the surface-adsorbate interactions of SnO2 material. Firstly, the pre-adsorption of oxygen on SnO2 (110) surface was modeled and analyzed, it was proved that the spontaneous adsorption O2 molecule and O atom could take place more easily on SnO2 (110) reductive surface than SnO2 (110) oxidative surface, and O2 molecule has more obvious tendency to be dissociated when adsorbed on SnO2 (110) reductive surface. Secondly, in consideration of the actual existence of oxygen vacancy, the pre-adsorption of oxygen on SnO2 (110) reductive surface with oxygen vacancy was conducted. The dissociation and ionization of O2 molecule were observed when molecular oxygen was adsorbed above the in-plane oxygen vacancy vertically on SnO2(110) reductive surface, which further verified the spontaneous adsorption of O2 molecule and the assumption for O− or O2− species. At last, the VOC gases adsorption properties including ethanol, methanol, formaldehyde and so on were carried out, the results revealed that ethanol was the easiest to be adsorbed on SnO2 material and hence might show better gas sensing properties than the other target gases, which is broadly in line with the experimental data.