Plasma-catalysis: Is it just a question of scale?

Abstract

The issues of describing and understanding the changes in performance that result when a catalyst is placed into plasma are discussed. The different chemical and physical interactions that result and how their combination might produce beneficial results for the plasma-catalytic processing of different gas streams are outlined with particular emphasis being placed on the different range of spatial and temporal scales that must be considered both in experiment and modelling. The focus is on non-thermal plasma where the lack of thermal equilibrium creates a range of temperature scales that must be considered. This contributes in part to a wide range of inhomogeneity in different properties such as species concentrations and electric fields that must be determined experimentally by in situ methods and be incorporated into modelling. It is concluded that plasmacatalysis is best regarded as conventional catalysis perturbed by the presence of a discharge, which modifies its operating conditions, properties and outcomes often in a very localised way. The sometimes used description "plasma-activated catalysis" is an apt one.

Fundamental Properties and Applications of Dielectric Barrier Discharges in Plasma‐Catalytic Processes at Atmospheric Pressure

“…A large variety of comprehensive reviews dealing with the wide field of plasma catalysis has been published during the last decades [6,7,[21][22][23][24][25][26][27][28][29][30][31]. Some of them focus on particular applications such as the oxidation of VOCs [7], while others emphasize the importance of modeling and simulation to understand plasma catalysis [24].…”

Plasma-driven catalysis: green ammonia synthesis with intermittent electricity

“…Previously, such mutual influences of the plasma and the catalyst were extensively discussed by Neyts et al 125,228,229 and Kim et al 219 Recent modelling investigations and characterization have provided novel insights. 230,231 This subsection sets the stage for the assessment of plasma-catalytic ammonia synthesis.…”

“…However, plasma-catalyst interactions and synergies thereof are not trivial to uncover, as the underlying principles of plasma catalysis are not fully understood. 231,233,234 Various possible plasma-catalyst interactions have been proposed for ammonia synthesis, as shown in Fig. 8.…”

“…A multidisciplinary approach is required to understand the mutual influence of the plasma and the catalyst, 219 covering various time-scales and length-scales. 90,231,235,236 So far, most information is obtained by macroscopic performance testing of plasma catalysis reactors. Van Durme et al 237 were the first to systematically categorize the mutual influence of a plasma and a catalyst, a topic heavily discussed thereafter.…”

Effects of oxygen-containing functional groups on the synergy effect in pulsed bipolar plasma-catalytic reactions of volatile organic compounds

“…The interaction between plasma and catalyst is highly complex because their interaction occurs at a far-fromequilibrium state. Whitehead 26,27 described various interactions between plasma and the catalyst, effects of catalysts on the properties of the discharge, and changes in the performance of the catalyst. Neyts et al 6 reported that relatively less information is available on the factors of observed synergy because the process of plasma catalysis is highly complex.…”