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.
The investigation by microkinetic simulations provide detailed reaction mechanisms about the NH 3 oxidation on the RuO 2 (110) surface. There are 41 elementary reactions involved in the microkinetic model in which all the thermodynamic and kinetic parameters are obtained from density functional theory (DFT) calculations, and the entropy effects of each reaction are considered in the simulation. The differences in reaction mechanisms between the batch type and the steady state were characterized in this study. The selectivities to the oxidation products, including N 2 , NO, and N 2 O, depend on the oxidation conditions. The simulated results show that the O 2 /NH 3 ratio, system temperature, and pressure are the controlling factors that could alter the results of the oxidation. The microkinetic modeling demonstrates how these parameters affect the NH 3 conversion and the selectivities. The simulations showed that N 2 and NO could be a primary product under different oxidizing conditions; however, N 2 O could only be a minor product because of the nature of its formation mechanism. The highest N 2 O selectivity obtained in the simulations is 30%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.