Abstract
Catalysts based on individual precious metals on carbon- and oxide-based carriers have shown remarkably selective behavior in the hydrodebromination of CH(2)Br(2) to CH(3)Br, an important transformation within halogen-mediated methane upgrading processes. However, the high susceptibility of the active phase to coking and to sintering, which cannot be overcome by controlling the nuclearity of the metal species, hinders their practical implementation. Herein, a platform of carbon-supported Ir-Ru catalysts with distinct metal ratios at comparable metal nanoparticle size (ca. 1.0 nm) was adopted to systematically study the effects of a second metal on reactivity and stability. Catalytic tests reveal ruthenium-doped iridium nanoparticles as the first system that combines high CH(3)Br selectivity (up to 93 %) with unprecedented stability, outperforming any of the previously reported catalysts. This superior performance was rationalized by the intimate interaction between the two metals, forming ruthenium-poor surface alloys, which enable suppressing deactivation mechanisms as well as over hydrogenation/coking pathways.