Single-Atom Zn Interface Engineering for Efficient Noble-Metal-Free Photocatalytic Non-Oxidative Coupling of Methane.

Abstract

ZnO-based photocatalysts have attracted extensive attention for methane (CH₄) conversion because their intrinsic internal electric field can effectively polarize and activate CH₄. However, the mismatch between charge-carrier dynamics and surface reaction kinetics limits the utilization of photogenerated reactive species, making noble-metal modification necessary to achieve efficient methane conversion. In this study, we report a noble-metal-free single-atom photocatalyst in which isolated Zn atoms are anchored onto anatase TiO₂ via µ-oxo bridges (Zn─O─TiO₂) for photocatalytic non-oxidative coupling of methane (NOCM). This structure not only promotes efficient charge separation and suppresses carrier recombination, enabling the formation of long-lived Zn⁺ and O^- reaction centers, but also provides active sites to accelerate surface reaction kinetics. Consequently, the catalyst achieves an ethane rate of 44.75 µmol·g^-1·h^-1 in a batch reactor, and 1.09 mmol·g^-1·h^-1 in a flow reactor. The apparent quantum efficiency reaches 8.81% at 350 nm. Mechanistic studies reveal that photogenerated holes at O^- centers activate CH₄ to CH₃ radicals, while electrons at Zn⁺ sites drive H₂ evolution, synergistically enabling efficient NOCM. This work establishes single-atom interface engineering as an effective strategy for simultaneously promoting charge separation and enhancing surface catalytic reaction, providing a general strategy for designing noble-metal-free photocatalysts for small-molecule activation.