A density functional theory study of reactions of relevance to catalytic hydrocarbon synthesis and combustion

Abstract

Synthesis and combustion of hydrocarbons on a series of metal surfaces (Ag, Au, Al, Cu, Rh, Pt and Pd) were investigated using density functional theory (DFT). The adsorption energies for all species involved in these reactions, as well as the reaction energies and activation barriers on these surfaces, were calculated using the same models and DFT methods. The results were used to test the validity of the Brønsted-Evans-Polanyi (BEP) and transition state scaling (TSS) relationships for these reactions on these metal surfaces. The BEP relationship appears to be a valid indicator for the synthesis reactions with R 2 values of 0.83, 0.88 and 0.94 for CO dissociation, CO hydrogenation and formyl (CHO) dissociation to CH + O, respectively. In addition to CH splitting, which has been studied before, the BEP relationship also appears to be valid for the CH oxidation and CHO dissociation to CO + H combustion reactions with R 2 values of 0.94, 0.89 and 0.88, respectively. Also, the TSS relationship is excellent with a R 2 value of 1 for all synthesis and combustion reactions. The BEP and TSS relationships were subsequently used to estimate the energetics of the synthesis and combustion reactions on Ni, Co and Fe surfaces. The results reveal that the transition state energies estimated by the TSS relationships are in better agreement with data obtained from DFT calculations than the activation energies estimated by the BEP relationships. Therefore, the TSS relationship is preferred when predicting energetics of these reactions on these surfaces.

Mechanistic and microkinetic study of non-oxidative methane coupling on a single-atom iron catalyst

“…The Brønsted–Evans–Polanyi (BEP) relation was also applied to the scaling, but this approach was found to be much weaker than both transition-state scalings, showing R 2 values of 0.19, 0.01, 0.87, and 0.88, respectively. Although the transition-state scaling was not necessarily stronger than the BEP relation 12 , previous studies have shown that the transition-state energies of particular surface reactions, such as hydrocarbon combustion and formation at high temperatures, are more suitably estimated by transition-state scaling 13 , 14 . According to Hammond’s postulate 15 , we can speculate that the transition states are structurally more similar to the initial states than to the final states.…”

Functionalized Electrochemical Aptasensor for Sensing of Ochratoxin A in Cereals Supported byin SilicoAdsorption Studies

“…Calculated negative adsorption energies indicate stabilization and an exothermic adsorption process. 89,90 The lower the negative energy, the stronger the adsorption between the adsorbate and substrate. On the basis of the increase in the anodic peak current observed at E pa = +0.3 V in Figure 3 (ii) of our nanocomposite, the presence of the aptamer greatly contributes to its stabilization.…”