Tailoring Methane Oxidative Coupling Pathways through Cluster-Modified Photocatalysts

Photocatalytic methane coupling represents a promising strategy for the production of valuable C₂₊ chemicals. Herein, the rational design of an Au₂₄Zn₁ nanocluster-embedded ZnO catalyst was demonstrated to enhance photocatalytic performance, and the resultant Au₂₄Zn₁/ZnO catalyst exhibited a C₂₊ selectivity of 93.5% and a yield of 663.1 μmol·g_cat^-1·h^-1 (510.1 mmol·g_Au^-1·h^-1) in a batch reactor. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy-CO adsorption (CO-DRIFTS) revealed that the clusters functioned as hole acceptors, thereby accelerating the separation of photogenerated carriers. Radical experiments and isotope-labeling studies confirmed that the •OH radical derived from water serves as the primary reactive oxygen species responsible for activating methane to •CH₃ radicals under the coexistence of H₂O and O₂, which demonstrates a significant discrepancy compared to the reported photogenerated hole activation pathway. Additionally, the •OOH radical generated via oxygen reduction played a supporting role both in modulating the concentration of •OH radicals and promoting the catalytic cycle. The cooperation contributed to the high yield and excellent selectivity of the C₂₊ products. This work provides valuable insights into the mechanistic pathway of methane conversion and highlights the potential of metal nanocluster-based materials in photocatalysis.