Highly Selective Photo-Oxidation of Methane to Methanol by Fe–Au Site-Supported SrTiO3 Hollow Nanotubes with Oxygen Vacancies

Abstract

Solar-driven methane (CH₄) conversion to value-added chemicals with high selectivity remains a long-standing challenge. Here, we present closely attached atomically dispersed Fe species and ultrafine Au-supported SrTiO₃ hollow nanotubes with oxygen vacancies (STO_v) for highly selective CH₄ conversion to CH₃OH. An impressive CH₃OH production rate of 7.53 mmol g^–1 h^–1 with a selectivity up to 95.4% has been achieved, corresponding to an apparent quantum efficiency of 15.8% at 365 nm, representing a record among all of the representative photocatalysts under comparable conditions. Experimental results and theoretical simulations elucidate that the created oxygen vacancies on SrTiO₃ without Ti³⁺ facilitate CH₄ adsorption to effectively capture photogenerated holes for producing methyl radicals. In parallel, the photogenerated electrons could be rapidly extracted by the anchored Au and then transferred to the adjacent single-atom Fe sites for activating O₂ to generate the key intermediate Fe–*OOH toward highly selective CH₃OH production. Significantly, a commendable electron transfer efficiency of 67.5% for O₂ activation is achieved on Fe–Au/STO_v based on the quantitative in situ microsecond transient absorption spectra. This work provides a deep understanding of the regulation of both activity and selectivity by the engineering of adjacent sites and the investigation of electron kinetics for O₂ activation during CH₄ photo-oxidation.