(114h) Consequences of Non-Thermal Plasma Stimulation on Catalyst Reactivity

Non-thermal, plasma-assisted catalysis has emerged as an alternative strategy to facilitate chemical transformations under mild conditions, driven by electrical energy. Integrating a catalyst into a plasma system can direct reactions and enhance reaction rates under ambient temperatures and pressures. However, experiments are often overshadowed by significant contributions from plasma-phase reactions that in many cases dominate the plasma-catalysis results. Further, the catalyst can be impacted by exposure to the plasma phase, resulting in sintering or changes in surface structure. To understand the influence of plasma-catalyst interactions on the observed chemistry, it is important to distinguish plasma-phase reactivity from the plasma-catalysis reactions occurring on the surface of the catalyst. Our group has adopted a sequential dosing methodology to separate plasma-phase reactions from surface-mediated pathways. In this presentation, we will discuss two cases: 1) nitrogen non-thermal plasma stimulation of supported metal catalysts followed by thermal reactions with hydrogen (or oxygen) to drive ammonia (or NOx) synthesis, and 2) in situ and ex situ characterization of hydrogen non-thermal plasma treated, supported metal catalysts to identify changes in catalyst structure and function. Through these experiments, we discern that plasma-assisted activation of nitrogen creates reactive surface nitrogen species that can be coupled to reactive gases, and product desorption peaks are sensitive to the selection of the metal catalyst. Additionally, from hydrogen plasma stimulation experiments, we observe the typical effects associated with strong-metal support interactions but induced by low temperature plasma stimulation. Collectively, these results highlight the potential of plasma stimulation for nitrogen conversion under ambient conditions, while underscoring the potential for plasma-catalyst interactions to alter the nature of the catalyst under plasma exposure.