Adsorption and decomposition of NO on O-covered planar and faceted Ir(2 1 0)

Reduction of NO by CO on Unsupported Ir: Bridging the Materials Gap

“…Significantly, on faceted Ir(210), N 2 is desorbed in two features: a prominent peak together with a small shoulder on the low-temperature side, in contrast to the one feature seen for NO on clean faceted Ir(210). [27] On planar Ir(210), N 2 is desorbed in a very narrow peak with a surface explosion feature, as described above, in contrast to the broad N 2 peak from NO on clean planar Ir(210). [27] The marked differences in the TPD spectra of N 2 on both surfaces in Figure 5 from those generated by decomposition of NO on clean planar and faceted Ir(210) [27] are indicative of strong local interaction between coadsorbed NO and CO on planar and faceted Ir(210), which is most likely governed by competition of NO and CO for the surface electron density available for backdonation into the corresponding 2p* orbitals.…”

“…Size effects were also not found in CO oxidation by pre-adsorbed oxygen [26] and dissociation of NO [27] on faceted Ir(210) (5-14 nm). The absence of size effects in reduction of NO by CO at 0.2 ML CO is consistent with the absence of size effects in dissociation of NO on clean faceted Ir(210) [27] since pre-adsorbed CO at this level does not affect dissociation of NO as concluded above. The observation of size effects in re- duction of NO by CO on faceted Ir(210) at 1 ML CO ( Figure 6) may be due to stabilization of NO by pre-adsorbed CO on Ir edge and corner atoms between the boundaries of the facets on faceted Ir(210).…”

“…Faceted Ir(210) is more active for reduction of NO by CO with higher selectivity to N 2 than planar Ir(210), as evidenced by less desorption of NO and N 2 O from faceted Ir(210). Comparison with the TPD spectra from the decomposition of NO on clean planar and faceted Ir(210) [27] leads to the conclusion that the N-containing TPD spectra on both surfaces in Figure 4 resemble those from NO on the clean Ir surfaces at low NO exposure, that is, pre-adsorbed CO at this level essentially does not affect NO dissociation. Thus, the rate-limiting step for reduction of NO by CO on both surfaces is NÀO bond breaking, whereby formation of N 2 and CO 2 proceeds through NO dissociation (NO!N + O) followed by recombination and desorption of N yielding N 2 and reaction of O with CO producing CO 2 .…”

A DFT study of the NO dissociation on gold surfaces doped with transition metals

“…The comparison of data calculated for the doped surfaces suggests a rather local character for the NO-surface interaction. For instance, the calculated adsorption energies for NO on pure Ir surfaces are of about 3.0 eV, 69 which is not far from the calculated energies for NO on Ir@Au(111), E ads = −2.79 eV and on Ir@Au(110), E ads = −3.26 eV.…”

“…The choice of the Ir and Rh doping elements is based on previous works where it was found that these elements are able to stabilize the adsorption of the reactants and to reduce the activation energies barriers for N-O bond dissociation. 53,54,69 The choice of the Ni (cheap metal) and Ag (frequent metal in catalysts) elements is also based on previous studies where it was found that these metals seem to be good catalysts for the dissociation of O-X bonds (X = H, N, or O). [70][71][72] …”