(691f) Understanding Plasma Catalysis, Using Multi-Modal Operando Spectroscopy

Non-thermal, atmospheric pressure plasmas produce ions, electrons, radicals, and vibrationally-excited molecules that are not normally present at thermal equilibrium at low temperatures. These reactive species could be exploited to drive chemical transformations that are otherwise difficult or impossible, by integrating a plasma into a catalytic system. In order to exploit the full potential of plasma catalytic systems, a fundamental understanding of plasma-catalyst interactions should be gained. In this talk, I will describe a novel multi-modal operando spectroscopy technique that we are developing to probe plasma-catalyst interactions in-situ under realistic operating conditions. The tool consists of a reactor unit that has ZnSe windows to allow for spectroscopic characterization of catalyst surfaces using polarization-modulation infrared-reflection absorption spectroscopy (PM-IRAS). The commercial reactor unit has been modified (1) to incorporate a dielectric barrier discharge plasma jet that impinges reactive plasma species onto the catalyst surface; and (2) to allow additional optical access to the gas-phase plasma for characterization by optical emission spectroscopy (OES). This tool is capable of performing three measurements simultaneously in the presence of a plasma: (1) characterization of excited species in the plasma-phase using OES; (2) detection of surface-adsorbed intermediates using PM-IRAS; and (3) detection of gas-phase products using mass spectrometry. Thus, this technique can correlate plasma-phase chemistry to surface chemistry and ultimately to final products. This is a unique tool for studying plasma-catalyst interactions, which could enable a more rational design of plasma-assisted catalytic processes.