Plasma Catalysis Modeling: How Ideal Is Atomic Hydrogen for Eley–Rideal?

The Journal of Physical Chemistry C, vol. 128, pp. 11196–11209

Abstract

High Resolution Image Download MS PowerPoint Slide Plasma catalysis is an emerging technology, but a lot of questions about the underlying surface mechanisms remain unanswered. One of these questions is how important Eley–Rideal (ER) reactions are, next to Langmuir–Hinshelwood reactions. Most plasma catalysis kinetic models predict ER reactions to be important and sometimes even vital for the surface chemistry. In this work, we take a critical look at how ER reactions involving H radicals are incorporated in kinetic models describing CO 2 hydrogenation and NH 3 synthesis. To this end, we construct potential energy surface (PES) intersections, similar to elbow plots constructed for dissociative chemisorption. The results of the PES intersections are in agreement with ab initio molecular dynamics (AIMD) findings in literature while being computationally much cheaper. We find that, for the reactions studied here, adsorption is more probable than a reaction via the hot atom (HA) mechanism, which in turn is more probable than a reaction via the ER mechanism. We also conclude that kinetic models of plasma-catalytic systems tend to overestimate the importance of ER reactions. Furthermore, as opposed to what is often assumed in kinetic models, the choice of catalyst will influence the ER reaction probability. Overall, the description of ER reactions is too much “ideal” in models. Based on our findings, we make a number of recommendations on how to incorporate ER reactions in kinetic models to avoid overestimation of their importance.

Authors 4

1. Roel Michiels

   University of Antwerp

   Affiliation as printed

   Research group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, Wilrijk,Antwerp BE-2610, Belgium

2. Nick Gerrits corresponding Aachen Leiden Institute of Chemistry, Gorlaeus Laboratories

   Leiden University · University of Antwerp

   Affiliation as printed

   Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, Leiden 2300 RA, The Netherlands

   Research group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, Wilrijk,Antwerp BE-2610, Belgium

3. Erik Cornelis Neyts

   University of Antwerp

   Affiliation as printed

   Research group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, Wilrijk,Antwerp BE-2610, Belgium

4. Annemie Bogaerts corresponding

   University of Antwerp

   Affiliation as printed

   Research group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, Wilrijk,Antwerp BE-2610, Belgium