Exposure of Rh+(CO)(2) on Rh/Al2O3 to NO causes CO desorption and adsorption of NO as Rh-NO+; exposure of Rh+(CO)(2) to NO/H-2 produced N2O at 573 K, The presence of both reductant (i.e., CO) and oxidant (i.e., NO or O-2) in the reactant pulse is needed to initiate and sustain the NO-CO redox reaction cycle for CO2 formation. (C) 2000 Academic Press.