A new aspect of heterogeneous catalysis: Highly reactive cis-(NO)2 dimer and Eley–Rideal mechanism for NO–CO reaction on a Co-dimer/γ-alumina catalyst

A catalytic aspect, ‘surface catalytic NO reactions assisted by gas phase CO molecules’ on a Co2+-ensemble/γ-Al2O3 catalyst, was elucidated by successive density functional theory (DFT) calculations on a Co2+-dimer/γ-Al2O3 model surface. Unique cis-(NO)2 dimeric species formed due to a specific alignment of the unoccupied orbitals on the Co2+-dimer, whose vibrational frequencies were almost identical to those for conventional gem-dinitrosyl species. The cis-(NO)2 species showed much higher reactivity with CO than the gem-dinitrosyl species, through the 2π∗–2π∗ bonding between the two NO adsorbates. Detailed DFT calculations for the reaction pathways indicated an Eley–Rideal mechanism with an unusually large reactive cross-section.