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

Abstract 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.

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