Reactions of Nb2 and Nb3 with CO, D2, N2, and O2: Reconciling experimental kinetics with density functional theory-calculated reaction profiles

Abstract

Calculated energy profiles for the reactions of neutral Nb(2) and Nb(3) metal clusters with CO, D(2), N(2), and O(2) are presented. In each reaction path, both a physisorption energy minimum, where the reactant remains intact, and a chemisorption energy minimum, where the reactant has dissociated, are calculated and linked by saddle points. We calculate branching ratios for the forward (dissociative) and reverse reactions which we compare with the experimental kinetic data. It is found that a combination of average thermal energies and barrier heights leads to wide variation in branching ratios which compares favourably to previously determined experimental reaction rates.

Adsorption and dehydrogenation of ammonia on vanadium and niobium nitride cluster cations

“…Here, the evaluation of the vacancy effect would provide valuable information for the design of novel nitride catalysts. Thus far, there have been many mass-spectrometric experiments on the reactions of gas-phase vanadium and niobium clusters with N 2 [18][19][20][21][22][23] and the firstprinciples calculations of structures of V n N 2 and Nb n N 2 [22,24,25]. However, the reactivity studies of clusters (even monomers) of vanadium and niobium and their nitrides toward ammonia are quite limited.…”

Enhanced Stability of Rhombic Dodecahedron Nb15– with Well-Organized Superatomic States

“…This was demonstrated to be consistent with its relatively larger HOMO–LUMO gaps and ionization energy. , Among others, the dehydrogenation of the mono-, di-, and trimethyl-substituted benzenes on cationic niobium clusters was studied by an FT-ICR mass spectrometer, showing dramatic size dependence of partial or complete dehydrogenation for these clusters . Extensive studies have also been devoted to understanding size-dependent stability and properties of niobium-involved clusters and complexes. − For example, photoelectron spectra of the anionic niobium clusters Nb n – and doped systems were studied, showing a variety of patterns correlated with geometrical structures. − However, the magic number of ionic niobium clusters has not been experimentally identified by far to the best of our knowledge.…”

Reactions of N2O and CO on neutral Rh10On clusters: a density functional study

“…Many of these studies have been motivated by the use of rhodium in automotive three-way catalytic converters 9 and the reactions of N 2 O, [10][11][12] NO, [13][14][15][16][17][18][19][20][21][22] CO 23,24 and CO 2 25 have been extensively investigated on both pure and doped [26][27][28] rhodium clusters. Given that spectroscopic methods such as infrared multiple photon dissociation spectroscopy (IRMPD) 29 use mass spectroscopy to identify the species of interest, they generally provide information only about the products of reactions and reactivity studies therefore often include computational investigation, 30,31 typically using density functional theory (DFT), but sometimes including higher level methods such as CCSD(T). 32 Two particular reactions that are of interest for automotive catalytic converters are the reduction of NO x to N 2 and the oxidation of CO to CO 2 .…”