Azomethane Decomposition Catalyzed by Pt(111):  An Example of Anti-Brönsted−Evans−Polanyi Behavior

Abstract

The molecular mechanism of azomethane decomposition on a clean Pt(111) surface has been studied by means of a periodic density functional theory (DFT) approach. Three main elementary steps have been considered, which imply either N-N or C-N scission. The thermodynamic order of stabilities suggests that the most favored reaction involves N-N scission into two methylnitrene NCH 3 adsorbed species. However, it is found that kinetic effects play a crucial role and the most favored reaction appears to be that leading precisely to the less stable reaction product. A similar trend is found for the other two explored reaction pathways: the less the stability of the resulting product, the lower the corresponding energy barrier. Therefore, the reaction mechanism is found to obey an anti-Bro ¨nsted-Evans-Polanyi relationship. Implications for surface-catalyzed reactions are discussed.

Accounting for van der Waals interactions between adsorbates and surfaces in density functional theory based calculations: selected examples

“…A similar arrangement but on the Pt(111) surface was found also for azomethane. 81 To estimate the magnitude of these interactions, the authors employed the semi-empirical van der Waals correction term proposed by Grimme 18 which was simply added to the total energy at different distances from the surface with the molecular geometry fixed at the optimum predicted by the calculations with the PBE exchange-correlation potential. This allowed the authors to obtain an estimate of its effect on the equilibrium distance from the molecule to the surface and of its contribution to the adsorption energy.…”

A Minimal Cluster Model of Valence Electrons in Adatom-Assisted Adsorbed Molecules: NCH3/Cu(110) and OCH3/Cu(110)

“…Thus, single-point calculations were performed for the IE. (2) The core electrons of the Cu atom do not participate in ionization below 10 eV, and an effective core potential of the LANL2DZ 37−39 basis was used for Cu. (3) CISD was adopted to include the final state interaction.…”

“…In this study, we will select methylnitrene (NCH 3 ) on Cu(110) as our probing system. Characterizing this system is fundamentally significant to understand several catalytic processes. − Previously, it has been found that azomethane (CH 3 NNCH 3 ) adsorbed on Cu(110) in ultrahigh vacuum decomposes into NCH 3 at room temperature, and the stable existence of the decomposed NCH 3 on Cu(110) has been identified by vibrational spectra, temperature-programmed desorption, UPS, and scanning tunneling microscopy (STM). , Moreover, quite recently, we have proposed the most plausible structure of this adsorption system based on density functional theory (DFT) calculations and STM imaging . We discovered that a key feature of its bonding is that each NCH 3 does not form a bond to the flat Cu(110) directly but that to the Cu adatoms through the N–Cu bonds.…”

Four Generations of Volcano Plots for the Oxygen Evolution Reaction: Beyond Proton-Coupled Electron Transfer Steps?

“…52 The approximation of the electrocatalytic activity based on heuristic descriptors such as η TD , ESSI, and G max (U) relies on the assessment of adsorption free energies, whereas the kinetics in terms of the transition states is assumed to scale with the thermodynamics by the BEP relation. Given that deviations from the BEP relation have been reported in the literature, 53 it might be of relevance to expand the volcano concept toward an unbiased integration of the kinetics. On the one hand, this train of thought violates the notion of a heuristic approach as the inclusion of transition states requires the calculation of the entire free-energy landscape along the reaction coordinate instead of simplifying it to the thermodynamic picture only.…”