Effective sensing mechanisms of O2 and CO on SnO2 (110) surface: a DFT study

Abstract

The dissociative adsorption of O₂ on SnO₂ is pivotal for its gas-sensing performance, yet the underlying mechanisms remain open to debate, limiting widespread applications. In this study, we introduce a novel mechanism that advances the understanding of gas adsorption and activation on metal oxide semiconductor surfaces, coupling O₂ dissociation and CO oxidation in a unified process that redefines the Mars–van Krevelen mechanism. Detailed DFT simulations demonstrate that the electronic and structural properties of the SnO₂ (110) surface trigger the spontaneous stabilization of a neutral polaron upon oxygen vacancy formation, boosting O₂ activation and directly coupling its dissociation with CO oxidation, leading to a highly energetically favorable process. Our findings mark a paradigm shift in the understanding of O₂-driven gas-sensing technology and showcase how the polaron reduces activation barriers and stabilizes key intermediates, optimizing the catalytic cycle and enhancing sensor activity. This work paves the way for the development of high-performance SnO₂-based sensors by leveraging defect engineering and polaron dynamics.