Overcoming Surface Inactivation through Catalytic Design in Low-Temperature Plasma-Catalytic Conversion of Methane to Hydrogen

In this talk, we demonstrate how catalytic surfaces can be designed in plasma environments to convert methane (CH₄) to hydrogen (H₂) directly while limiting surface inactivation. Conventional methane conversion on catalysts forms layers of carbon (i.e., coking) that reduce catalytic activity and the rate of hydrogen production. In plasma environments, we show that coking does not result in complete catalytic inactivation, but instead, self-assembles into carbon filaments that grow off the surface. We employ a combination of in- (i.e., microscopy) and ex-situ diagnostic techniques (i.e., profilometry) to characterize the growth of carbon in real time on catalysts that are enveloped in plasmas. We utilize density functional theory (DFT) and microkinetic models to show how the design of catalysts can synergize with vibrational excitations of methane to break scaling relations and enable the use of more coke-resistant catalysts. Experiments are repeated to validate these predictions and show how the design of catalysts can further change how carbon is deposited and localized on surfaces. In each case, we quantify H₂ production near catalytic surfaces through argon (Ar) actinometry with optical emission spectrometry (OES) and gas chromatography to evaluate the process efficiency. This research offers insights into the relationship between plasmas and catalysts in environments where surface morphologies change dynamically.