Plasma Diffuse Reflectance Infrared Fourier Transform Spectroscopy Cell Design and Experimental Set-Up for Operando-DRIFTS Investigations on Plasma-Induced Heterogeneous Catalyzed Reactions

Herein, the development and application of a customized nonthermal plasma diffuse reflectance infrared Fourier transform spectroscopy cell based on the Harrick reaction chamber is presented, which integrates a miniaturized dielectric barrier discharge (DBD), implemented in a Bruker Invenio S Fourier transform infrared spectroscopy (FTIR) spectrometer. The one-sided closed electrode-tube arrangement, mounted in a PEEK cylindrical holder, is inserted through the observation window. The stable operation of AC-driven (10.6 kHz) dielectric barrier discharges in binary gas mixtures of argon and CO₂ is monitored by electrical measurements, which also allows the determination of the discharge power. The gas outlet is connected to a mass spectrometer for online quantitative product gas analysis, enabling operando FTIR spectroscopic studies of plasma-assisted heterogeneous catalyzed reactions. The impact of applied discharge voltage under the variation of the gas composition, gas flow, catalyst pretreatment procedure, and the distance between electrode and catalyst bed has been studied for the CO₂ splitting employing CeO₂ as a catalyst. The operando FTIR spectroscopic study of the plasma-assisted CO₂ dissociation suggests both an active CO₂ dissociation on the ceria surface and a plasma-induced reorganization of the catalyst surface structure. The results in terms of calculated specific energy input and CO₂ conversion correspond with the trends reported for this transformation in coaxial DBD reactors.