Electron Donation Enhanced CO Oxidation over Ru-Loaded 12CaO·7Al₂O₃ Electride Catalyst

It is widely recognized that CO oxidation effectively proceeds over Au nanoparticles supported on a reducible oxide, such as TiO₂ and Fe₂O₃, in which the support supplies oxygen during the reaction (Mars–van Krevelen (MvK) type mechanism). Here we examine the stable electride, [Ca₂₄Al₂₈O₆₄]⁴⁺(e^–)₄ (C12A7:e^–), with a low work function (2.4 eV), as a Ru catalyst support for CO oxidation. Ru-loaded C12A7:e^– exhibited more than a 3-fold higher turnover frequency (TOF) and a lower activation energy than Ru-loaded TiO₂, Al₂O₃, and [Ca₂₄Al₂₈O₆₄]⁴⁺(O^2–)₂ (C12A7:O^2–) catalysts. The high catalytic performance of Ru/C12A7:e^– is not due to the MvK type mechanism but to efficient electron transfer from C12A7:e^– to the species adsorbed on the Ru catalyst, in which the association reaction between adsorbed CO molecules and O adatoms is promoted on the Ru surface.