This paper reports the appraisal of two in situ Fourier Transform InfraRed plasma cells with respect to the interrogation of the glow of a non-thermal plasma (using a transmission cell), and the non-thermal plasma/solid (i.e. dielectric/catalyst) interface (with a reflectance cell). The paper also reports, for the first time, a direct comparison of the IR spectroscopy of plasmaand thermally-driven chemistry. The system chosen for study was the reduction of CO 2 as there is a wealth of data in the literature for comparison. The catalyst was Macor, a ceramic material comprising primarily Al, Si and Mg oxides. In both the thermal and plasma experiments, rotationally-excited CO 2 (CO Ã 2 ) was observed: in the plasma system, rotationally-excited CO (CO*) was produced via the reduction of CO 2 . Using the transmission cell, the conversion of CO 2 to CO was estimated and found to be up to 9% at energy efficiencies of ca. 1-2%, in line with the literature. No reaction of CO 2 was observed in the thermal system. The data obtained using the reflectance cell were similar to those obtained with the transmission cell, with the minor differences reflecting the longer residence time and higher specific input energy. Interestingly, two plasma-induced bands were observed in the reflectance experiments which increased in intensity with time and input power: these may be due transverse and longitudinal optical modes of SiO 2 and did not appear to participate in the observed chemistry.

This paper reports in situ Fourier transform infrared (FTIR) spectroscopic studies on the nonthermal plasma reaction of isopropyl alcohol in dinitrogen at Macor (a ceramic containing oxides of Al, Mg, and Si) and the analogous thermally driven process. While isopropyl alcohol did not react at the Macor at temperatures up to 600 °C, the study of the nonthermal plasma-driven process at the ceramic led to unexpected chemistry hitherto not observed, primarily the reaction of IPA in dinitrogen at short time scales to produce methane, HCN, acetone and "cold" CO at ca. 115 K. The CO, methane, and HCN rapidly established steady state concentrations, pointing to the need for faster FTIR studies: at longer times, isophorone and a "polymethylacetylene-like" polymer were formed as a brown oil. The observation of the steady-state gases and brown oil suggested parallel pathways in the plasma, the latter taking place at the plasma/catalyst interface, and the former in the plasma remote from the catalyst. Replacing dinitrogen with argon completely inhibited or negated the production of the oil, had no effect upon the processes taking place in the plasma remote from the Macor, and instead resulted in the production of acetylene.

In situ Fourier Transform Infra Red spectroscopy was employed to study the plasma glow region of a non-thermal plasma between two Macor dielectrics and fed with CO 2 , CH 4 and N 2 . CO, HCN and formaldehyde were produced and rapidly attained steadystate conditions. In addition, the chain oxides C 5 O 2 and ketene were observed (the first time such species have been seen in the dry reforming of methane) and a liquid film was produced comprising multiple components, one of which was acetamide. The data were interpreted in terms of catalysis by the Macor dielectric and a wholly novel, multizone model in which the liquid film plays a direct and important role. The data obtained in the plasma experiments were compared to an analogous, thermal experiment. Importantly, the results from this work could have major implications across the fields of catalysis, synthesis and origin-of-life chemistry.

This paper reports the application of in situ reflectance Fourier Transform InfraRed spectroscopy to the study of the thermal and plasma driven reaction of IsoPropyl Alcohol (IPA) at SnO2-coated Macor, the latter a ceramic material comprised of the oxides of Al, Mg and Si. The data so obtained were compared to those obtained using uncoated Macor. When uncoated Macor was employed, no reaction of the IPA was observed up to 600 °C in the thermal experiments, whereas a number of products were observed in the plasma-driven experiments. The results obtained using coated Macor were somewhat different, with no reaction taking place in the plasma-driven experiments, whilst significant reaction took place in the thermally-driven process. In the latter experiments, the chemistry was observed to show four distinct temperature regions, with electron injection into the conduction band of the SnO2 playing a significant role, culminating in the production of CO2. The data were interpreted in terms of a model in which physisorbed IPA was converted to two forms of isopropoxide: this was converted to acetone and acetaldehyde via adsorbed enolate. The data clearly support the catalytic activity of Macor in the plasma-driven conversion of IPA.

This paper reports on the thermally-driven and non-thermal plasma-driven reaction of IsoPropyl Alcohol (IPA) on ceria (CeO2) with the aim to investigate the differences between plasma catalytic interactions and the analogous thermal reactions.