Toward Elucidating the Role of Noble Metal Co-catalysts in Photocatalytic Oxidation of Methane to Methanol

The availability of methane as the principal component in the natural gas resources and a potent greenhouse gas calls for the development of efficient mitigation strategies for its conversion to value-added chemicals and fuels, such as methanol. Methanol is a key vector to fuel a future. And a direct methane-to-methanol conversion holds the promise as a drop-in replacement for the methane reforming, which is highly energy-intensive process.<br/>Activation of C-H bond in methane is the key step in the direct methane-to-methanol conversion, which has been demonstrated to benefit from the use of free radicals. Photochemical methane activation offers intriguing and vital opportunities by generating free radicals directly from water and oxygen and thus is promising for large scale fuel production. Such photocatalytic process involves the use of inorganic semiconductor catalysts and noble metals nanoparticles co-catalysts. Despite intensive studies, the photocatalytic methane oxidation faces the challenge of a limited selectivity toward methanol, and the catalytic functions of different noble metal co-catalysts remain largely unexplored.<br/>In this talk, on the basis of catalysts design, in-situ X-ray absorption spectroscopy, electron paramagnetic resonance and kinetic studies, we will discuss the relationship between the role of co-catalysts, the controlled generation and diffusion of free radicals, and the selectivity toward various liquid products. Such molecular-level insights are expected to facilitate the selective functionalization of light alkanes and offer informative design principles for photocatalysts.