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·gcat-1·h-1 (510.1 mmol·gAu-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.