Title : Microkinetic modeling of ammonia oxidation over Pt(211)- the role of the surface coverage

Abstract:

The effect of surface coverage (θ) on single NO^*, N^* and O^* and double NO^*–(N^*−Pt), NO^*−(O^*–Pt), N^*– (O^*−Pt) and O^*–(N^*−Pt) co-adsorbed systems on Pt(211) stepped surface has been studied by using periodic density functional theory (DFT). The effect of the surface coverage on the activation energies of elementary reactions for the ammonia oxidation network was also investigated at θ values of 1/12 and 1/6 mL, respectively. It was found that binding energy for single and double adsorption decreases almost linearly as θ increases. This effect is stronger for double co-adsorbed systems than for single adsorption cases. A threshold coverage (θ^T) of 0.08 mL for which the linear dependency of binding energies with θ will tail off was estimated. Activation energies also decrease as θ increases, with the lateral interactions between the reactants being the major contributor to the overall energy barrier. Finally, the results of this study permit the inclusion of the surface coverage effects not only on the enthalpies of reaction but also on the activation energies for products formation during ammonia oxidation modeling, ensuring the thermodynamic consistency.

Audience take-away:

• People working in chemical kinetics, catalytic activity and heterogeneous catalysis will learn how to use periodic molecular modeling to get insight into the reaction mechanism taking place at the catalytic surface.
• This research provides all the parameters needed to include the surface coverage effect in the microkinetic modeling of ammonia oxidation on platinum Pt(211) which appears to be a more active surface for product formation than the most thermodynamic stable facet Pt(111).
• Finally, with the results of this research, the microkinetic modeling of ammonia oxidation on platinum using chemical kinetics simulators such as Chemkin or Fluent can be carried out in a thermodynamically consistent way, avoiding fitting and other approximations that can result in inaccurate modeling of the catalytic process

Biography:

Dr. Juan David Gonzalez studied Chemistry at Antioquia University and graduated in 2008 with honors. He then joins Prof. Fanor Mondragon's research group at the Chemistry Institute of the same university to do a Master of Science in Chemistry. In 2013 he won the prestigious Australian Award and Australian Leadership Award to do his Ph.D. in Chemical Engineering at The University of Sydney. He received his Ph.D. in 2017. In 2018 he returned to his home country Colombia and obtained a position as an associate professor at Remington University.