Efficient and selective photocatalytic CH conversion to CHOH with O by controlling overoxidation on TiO.

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 into CHOH by O is carried out on Ag-decorated facet-dominated TiO. The {001}-dominated TiO shows a durable CHOH yield of 4.8 mmol g h 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. 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 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 → Ti-OO-Ti and Ti-(OO) → Ti-O pairs), thus achieving high selectivity and yield for CH photooxidation into CHOH.