Interaction of Nitric Oxide with Late 3d Transition Metals: Dissociation and Metal Oxidation

Heterogeneous interfaces influence chemical reactions by stabilizing the adsorption of reactive intermediates, lowering activation barriers of rate- and selectivity-determining steps. Here, we elucidate periodic trends in metal surface oxidation resulting from interaction with nitric oxide and subsequent adsorbate reaction chemistry across the late 3d transition-metal series with surface-sensitive ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and density functional theory calculations. Metals with open d-shell orbitals (e.g., Fe, Co) favor stabilization of nitric oxide dissociation products (nitrogen adatoms, N*), while metals having near (e.g., Ni) or completely (e.g., Cu) closed d shells promote nitric oxide oxidation toward nitrite and lower total nitrogen and N* coverage. Adsorbate core-level (O 1s and N 1s) binding energies capture electron localization around nitrogen, and eventually oxygen, as nitric oxide moves toward dissociation. Metal-nitride covalency increases with decreasing transition metal electronegativity, where nitrogen adatom binding energies decrease as the transition metal d-band is pushed toward the Fermi level. This work illustrates experimental and theoretical relationships between the nature of the d-band in facilitating nitric oxide adsorption and dissociation chemistry, furthering fundamental understanding of the role of metal electronic structure in determining catalytically relevant adsorption properties.