Methane-H₂S Reforming Catalyzed by Carbon and Metal Sulfide Stabilized Sulfur Dimers

H₂S reforming of methane (HRM) provides a potential strategy to directly utilize sour natural gas for the production of CO_x-free H₂ and sulfur chemicals. Several carbon allotropes were found to be active and selective for HRM, while the additional presence of transition metals led to further rate enhancements and outstanding stability (e.g., Ru supported on carbon black). Most metals are transformed to sulfides, but the carbon supports prevent sintering under the harsh reaction conditions. Supported by theoretical calculations, kinetic and isotopic investigations with representative catalysts showed that H₂S decomposition and the recombination of surface H atoms are quasi-equilibrated, while the first C-H bond scission is the kinetically relevant step. Theory and experiments jointly establish that dynamically formed surface sulfur dimers are responsible for methane activation and catalytic turnovers on sulfide and carbon surfaces that are otherwise inert without reaction-derived active sites.