Fabrication of Stepped CeO 2 Nanoislands for Efficient Photocatalytic Methane Coupling

Nonoxidative conversion of methane (NOCM) under mild conditions is a highly desirable technology for the low-carbon and atom-economical production of H 2 and value-added chemicals. Here, we report the fabrication of CeO 2 nanoisland patterns on the surface of Ce–Zr solid solutions. These ultrasmall CeO 2 nanoislands with abundant step-edge structures provide unprecedented methane adsorption and activation, achieving the highest methane conversion rate of 1517 μmol g –1 h –1 for photocatalytic NOCM to date. Density functional theory calculations revealed that the low-coordinated Ce–O units at the stepped CeO 2 (111) surface possess more open planar configurations, which facilitate the cleavage of methane C–H bonds via a distinct metal–CH 4 σ-complex mechanism that is energetically more favorable than the radical-like mechanism on the flat CeO 2 (111) surface. Moreover, the photocatalyst demonstrated a reversible and cooperative photoactivation process that enables the transition from the “resting state” to the “active state”, thereby enhancing the photoexcited charge separation efficiency and photocatalytic NOCM activities.