Unveiling the Dynamic Structure Evolution of In2O3(110) in the Direct Oxidation of Methane to Methanol
Direct oxidation of methane (CH4) to methanol (CH3OH) (DMTM) offers a value-added route for natural gas utilization but is constrained by poor reactivity and selectivity, necessitating efficient catalysts and accurate mechanistic understanding. This study investigates In2O3-catalyzed DMTM using first-principles calculations and the energetic span model (ESM). Considering the facile storage and release of lattice oxygen on In2O3, three surface states—stoichiometric (S-110), reduced (R-110), and reoxidized (O2-R-110)—were examined under identical conditions. The dynamic surface transformation S-110→R-110→O2-R-110 induces synchronous changes in CH4 activation mechanisms: polarization activation→σ* activation→σ activation, identified via electron transfer patterns between adsorbates and catalytic sites. The optimal site for non-stoichiometric DMTM emerges on S-110, and the binding ability of dual H atoms is found valid for describing reaction barriers and turnover frequency. Deciphering the complete DMTM pathway reveals that the Mars-van Krevelen+Eley-Rideal route is kinetically favorable according to ESM analysis, with low overoxidation tendency. This work provides insights for further optimization and design of DMTM catalysts from the perspective of surface geometry evolution.