Microkinetic modelling of post-plasma catalysis to improve the conversion of dry reforming of methane in a gliding arc plasmatron

Plasma conversion of the greenhouse gases CO₂ and CH₄ into useful products via dry reforming of methane (DRM) has shown promising results in gliding arc and other warm plasmas, but the conversions and product distribution can be further improved. In this work, we investigate the effects of adding a post-plasma Ni catalyst, to achieve extra CO₂ and CH₄ conversion via the catalytic DRM reaction. We developed a 0D microkinetic model to calculate gas-phase and surface reactions in the plasma, afterglow, and catalyst surface, which can be used to study both conversion trends, as well as the underlying reaction mechanisms. We examined a range of relevant parameters, and the results show an improvement in conversion, especially at high catalyst site density, catalyst bed gas temperature and fraction of gas converted by the plasma. At the optimal 30/70 CO₂/CH₄ input gas mixture, our model predicts an increase in conversion from 25 %, to 68 % and 43 % for CO₂ and CH₄, respectively, upon Ni catalyst addition. The pathway analysis reveals that adsorbed C atoms (C*) play a critical role, and upon recombination with O* into CO*, they link the CO₂ and CH₄ conversion mechanisms, albeit a balance must be maintained to avoid C*-poisoning. In addition, the pathway depends on the Ni facet, with most conversion taking place on Ni(1 1 0). Overall, our model demonstrates the positive effects of integrating post-plasma catalysis to a warm plasma, guiding experimental work to obtain the highest possible conversions, by tuning the input conditions.