Fabrication of Stepped CeO2 Nanoislands for Efficient Photocatalytic Methane Coupling

Nonoxidative conversion of methane (NOCM) under mildconditionsis a highly desirable technology for the low-carbon and atom-economicalproduction of H-2 and value-added chemicals. Here, we reportthe fabrication of CeO2 nanoisland patterns on the surfaceof Ce-Zr solid solutions. These ultrasmall CeO2 nanoislandswith abundant step-edge structures provide unprecedented methane adsorptionand activation, achieving the highest methane conversion rate of 1517 & mu;mol g(-1) h(-1) for photocatalyticNOCM to date. Density functional theory calculations revealed thatthe low-coordinated Ce-O units at the stepped CeO2(111) surface possess more open planar configurations, which facilitatethe cleavage of methane C-H bonds via a distinct metal-CH4 & sigma;-complex mechanism that is energetically more favorablethan the radical-like mechanism on the flat CeO2(111) surface.Moreover, the photocatalyst demonstrated a reversible and cooperativephotoactivation process that enables the transition from the "restingstate" to the "active state", thereby enhancingthe photoexcited charge separation efficiency and photocatalytic NOCMactivities.