Microkinetic Simulation of Temperature-Programmed Desorption

Abstract

The temperature-programmed desorption (TPD) spectra were simulated by combining density functional theory (DFT) calculations and microkinetic modeling. In the microkinetic analyses, all kinetic and thermodynamic parameters were obtained from DFT calculations to minimize artificial assumptions. For the case study, the desorptions of NH 3 and H 2 O from the RuO 2 (110) surface were simulated. The coverage-dependent desorption energies were introduced into the microkinetic model because different adsorbates on the surface will exhibit different desorption behaviors. In addition, temperature-dependent pre-exponential factors were applied to the desorption rate equations. The calculated preexponential factors are ranged from 10 14 to 10 17 s −1 , which are greatly larger than 10 13 s −1 , a generally accepted empirical value for desorption processes. The desorption temperatures obtained from microkinetic simulations consist with experimental results, and the simulated TPD patterns are also similar to the experimental observations.

Effective and Highly Selective CO Generation from CO2 Using a Polycrystalline α-Mo2C Catalyst

“…To further confirm the present assignments, Figure includes the experimental TPD profile and desorption peak temperatures calculated from the present theoretical models (see Tables and ). The simulation has been carried out for each of the identified minimum energy structures and using a similar approach to that applied and discussed in detail elsewhere. − Note that adsorption energies from PBE-D3 were used, as dispersion terms noticeably contribute to the strength of binding to the catalyst surface. The comparison in Figure shows that the observed broad temperature range for CO desorption is indeed explainable as consisting of superimposed desorption peaks from numerous exposed CO binding sites.…”

Understanding the Phase Diagram of Self-Assembled Monolayers of Alkanethiolates on Gold

“…Generally, it is possible to combine DFT data with a microkinetic model or a kinetic Monte Carlo algorithm to directly simulate a TPD experiment. , Such simulations have primarily been carried out for systems with adsorbates without hydrocarbon chains though. For extended thiolates additional complicating factors would arise relating to e.g.…”

Microkinetic Simulation of Ammonia Oxidation on the RuO2(110) Surface

“…In our previous study, 11 we derived the rate constants of adsorption (k ads ) and desorption (k des ) from the collision theory. They are (2)(3)(4) and the pre-exponential factor of the desorption process (ν des ) is…”

“…ads des (2)(3)(4)(5)(6)(7)(8)(9)(10)(11) In eq 2-10, E A is the energy of a single adsorbate in the gas phase, E RuO 2 is the energy of the clean surface, and E A/RuO 2 is the total energy of the adsorption system. A positive value of E des indicates an endothermic desorption process.…”