Identification of the Potassium-Related Species as the Key Active Sites for C–S Bond Couplings over K-MoS2 Materials

The coupling of C–S bonds is fundamental for the production of sulfur-containing chemical feedstocks in synthetic sulfur chemistry, while it remains a great challenge via heterogeneous catalysis over well-known transition metal-based catalysts. Herein, we identify that potassium polysulfides/oxy-sulfides/oxides (K–S(-O) species), the typical promoters, are the key active sites for coupling C–S bonds, while the vacancy-rich molybdenum disulfide (MoS2) phases are found to be promoters to form the interfacial “K–Sactive-Mov” species, which greatly reduce the activation energy barrier. The generation of the interfacial “K–Sactive-Mov” sites is demonstrated by integrated aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy. A structure–performance relationship between the active interfacial “K–Sactive-Mov” sites and the C–S coupling activity is established through qualitative and quantitative analysis. In situ diffuse reflectance infrared Fourier transform spectroscopy combined with density functional theory (DFT) calculations further confirms the formation of key COSH* and C–S related intermediates and reveals the reaction mechanism of C–S bond formation at the molecular level.