Efficient and selective photocatalytic CH4 conversion to CH3OH with O2 by controlling overoxidation on TiO2

• Published in: Nature communications Vol. 12; no. 1; pp. 4652 - 10
• Main Authors: Feng, Ningdong, Lin, Huiwen, Song, Hui, Yang, Longxiao, Tang, Daiming, Deng, Feng, Ye, Jinhua
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 02.08.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 140/131; 140/146; 147/143; 639/301/299/890; 639/638/77/885; 639/638/77/890; 639/925/357; Conversion; Electron paramagnetic resonance; Electron spin; Electron spin resonance; Fourier transforms; Humanities and Social Sciences; Infrared spectroscopy; Intermediates; Methane; multidisciplinary; NMR; Nuclear magnetic resonance; Oxidation; Oxygen; Photocatalysis; Photooxidation; Science; Science (multidisciplinary); Selectivity; Spin resonance; Titanium dioxide; Vacancies
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-24912-0

The conversion of photocatalytic methane into methanol in high yield with selectivity remains a huge challenge due to unavoidable overoxidation. Here, the photocatalytic oxidation of CH 4 into CH 3 OH by O 2 is carried out on Ag-decorated facet-dominated TiO 2 . The {001}-dominated TiO 2 shows a durable CH 3 OH yield of 4.8 mmol g −1  h −1 and a selectivity of approximately 80%, which represent much higher values than those reported in recent studies and are better than those obtained for {101}-dominated TiO 2 . Operando Fourier transform infrared spectroscopy, electron spin resonance, and nuclear magnetic resonance techniques are used to comprehensively clarify the underlying mechanism. The straightforward generation of oxygen vacancies on {001} by photoinduced holes plays a key role in avoiding the formation of •CH 3 and •OH, which are the main factors leading to overoxidation and are generally formed on the {101} facet. The generation of oxygen vacancies on {001} results in distinct intermediates and reaction pathways (oxygen vacancy → Ti–O 2 •  → Ti–OO–Ti and Ti–(OO) → Ti–O • pairs), thus achieving high selectivity and yield for CH 4 photooxidation into CH 3 OH. The photocatalytic conversion of CH 4 into CH 3 OH with high activity and selectivity must avoid product overoxidation. Here, authors minimize overoxidation by using a (001)-dominated TiO 2 nanosheet to circumvent CH 4 overoxidation intermediates plus reaction pathways that occur on (101) facets.