Tailoring facet sensitivity in anatase titania for selective photocatalytic oxidation of methane to formaldehyde
Di Hu, Jiaxin Chen, Xiufan Liu, Xinjie Song, Junnan Tao, Shuai Lyu, Siyang Li, Yuheng Jiang, Bastian Mei, Andreï Y. Khodakov
Abstract
Photocatalytic methane oxidation is a promising route to produce formaldehyde, yet achieving high efficiency, selectivity, and stability with cost-effective systems remains challenging. Here, we uncover facet sensitivity in the methane photocatalytic oxidation over anatase TiO 2 {001}/{101} junctions. The truncated octahedral bipyramid, exposing 62 % {001} and 38 % {101} facets, exhibits superior photocatalytic performance for methane-to-formaldehyde conversion under ambient conditions. Band structure, carrier dynamics, and mechanistic studies reveal that surface-bound methoxy species (OCH 3 ) act as key intermediates, facilitated by enhanced charge separation and transfer across the {001}/{101} facet junctions. The higher OCH 3 /•OH (hydroxyl radicals) ratio promotes selective methane oxidation to HCHO while suppressing deep oxidation to CO 2 . Furthermore, integration into a microtube reactor with optimized light harvesting and gas–solid–liquid mass transfer boosts performance, achieving a high formaldehyde production rate of 280 mmol g cat −1 h −1 L −1 (2.24 µmol h −1 ) with 100 % selectivity in liquid-phase. This work offers an efficient and scalable approach to catalyst and process engineering for sustainable formaldehyde production via photocatalytic methane conversion. • Facet sensitivity in the methane oxidation over anatase TiO 2 {001}/{101} junctions. • Surface-bound methoxy species (*OCH 3 ) act as key intermediates. • Integration into an optimized microtube reactor boosts the performance. • 100 % formaldehyde selectivity in the liquid phase has been achieved.