Fabrication of Stepped CeO2 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 H2 and value-added chemicals. Here, we report the fabrication of CeO2 nanoisland patterns on the surface of Ce–Zr solid solutions. These ultrasmall CeO2 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 CeO2(111) surface possess more open planar configurations, which facilitate the cleavage of methane C–H bonds via a distinct metal–CH4 σ-complex mechanism that is energetically more favorable than the radical-like mechanism on the flat CeO2(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.