Selective Photocatalytic Oxidation of Methane to Methanol by Constructing a Rapid O₂ Conversion Pathway over Au–Pd/ZnO

Abstract

Photocatalytic oxidation of methane to methanol is an attractive process under mild conditions, nevertheless confronting significant challenges in achieving high conversion and selectivity simultaneously. Herein, we propose a strategy for the direct and rapid generation of hydroxyl radicals ( • OH) from O 2 (O 2 → *OOH → • OH) by rational design of Au−Pd/ZnO photocatalyst, skipping water-soluble H 2 O 2 and avoiding H 2 O 2 diffusion. For photocatalytic methane oxidation at ambient temperature, the yield and selectivity of CH 3 OH over the optimized 1.0% AuPd 0.5 /ZnO catalyst were as high as 81.0 μmol•h −1 and 88.2%, respectively, exceeding that of most reported systems. The formation of Au−Pd alloys could improve the O 2 adsorption and the cleavage of the O−O bond in *OOH, facilitating the efficient direct formation of • OH and increasing the CH 3 OH yield and selectivity. This work provides some guidance for the delicate design of composite photocatalysts for efficient selective photocatalytic methane oxidation and O 2 utilization.

Unveiling the Mechanism of Plasma-Catalyzed Oxidation of Methane to C2+ Oxygenates over Cu/UiO-66-NH2

“…The strong bonds make it thermodynamically unfavorable to directly convert CH 4 and CO 2 to liquid products. As a result, an indirect two-step approach is typically employed, involving the energy-intensive dry reforming of methane (DRM) into syngas (a mixture of CO and H 2 ) at high temperatures (>700 °C), followed by Fischer–Tropsch synthesis to produce liquid fuels and chemicals under high pressures. − From an economic and energy-saving standpoint, direct conversion of CH 4 and CO 2 into liquid products under mild conditions is highly desirable, but it remains a significant challenge due to the thermodynamic limitations and the need for efficient catalysts that can facilitate the selective activation of these stable molecules. , …”

“… 5 − 8 From an economic and energy-saving standpoint, direct conversion of CH 4 and CO 2 into liquid products under mild conditions is highly desirable, but it remains a significant challenge due to the thermodynamic limitations and the need for efficient catalysts that can facilitate the selective activation of these stable molecules. 9 , 10 …”