A planar volume dielectric barrier discharge (DBD) in pure carbon dioxide (CO₂) for the formation of carbon monoxide (CO) is examined by combined electrical and CO density measurements. The influence of the type of electrode, the barrier material, the barrier thickness, and the discharge gap on the plasma power and the CO formation is analyzed systematically. The electrical characterization by means of charge-voltage plots is based on the simplest equivalent circuit model of DBDs, extended by the so-called partial surface discharge effect and the presence of parallel parasitic capacitances. The stackable discharge arrangement in this study enables one to elucidate the influence of parasitic capacitances, which can be overlooked in the application of such plasma sources. The determination of the discharge voltage from charge-voltage plots and the validity of the so-called Manley power equation are revised by taking into account non-uniform coverage as well as parasitic capacitances. The energy yield ($EY$) of CO is analyzed and compared with the literature. No correlations of $EY$ with the mean reduced electric field strength or the geometric parameters of the DBD arrangement are observed.

The formation of carbon monoxide, oxygen and ozone in a barrier corona discharge (BCD) operating in pure carbon dioxide (CO₂) and binary mixtures of CO₂ and argon is studied. The asymmetric electrode configuration of the BCDs allows plasma operation at pressures exceeding 1 atm, up to 6 bar, at moderate high-voltage amplitudes below 15 kV. Charge–voltage plots and an equivalent circuit model are employed to characterize the electrical parameters at different pressures and gas compositions. Depending on these conditions and the voltage amplitude, full or partial coverage of the electrodes with plasma is obtained. The existence of an optimum pressure for power dissipation for each given operation voltage amplitude and gas composition can be confirmed and explained by the equivalent circuit model. Increasing the CO₂ concentration in the working gas increases the mean reduced electric field strength E/N while pressure reduces it in the BCD. The CO₂ conversion shows a maximum efficiency of about 4% at 1.5 bar for the gas mixture Ar/CO₂ = 1:1 and a voltage amplitude of about 10 kV. The calculation of thermodynamic equilibrium parameters reveals that a relatively small increase in pressure can affect both, the equilibrium parameters and the reaction rates. As a result, the specific required energy for the reaction ( $$\Delta \mathrm{H}/\mathrm{SEI}$$Δ H / SEI ) shows an optimum, but only 8% of the electrical input energy is spent for CO₂ dissociation at these optimum conditions.

A comparative evaluation is reported of the performance of different discharge regimes—AC powered dielectric barrier discharge (DBD) and DC powered corona discharge of positive (DC+) and negative (DC−) polarity—implemented within the same reactor, a benchtop prototype for an advanced oxidation stage in water treatment. For all three modes of operation, DBD, DC+ and DC−, the reactor performance was tested using phenol as model pollutant and determining the process energy efficiency ( k _E and G ₅₀ ), kinetics ( t _1/2 ), nitrated byproducts and extent of mineralization to CO ₂ . Finally, comparison with a smaller DBD reactor of similar configuration previously used in our lab (Marotta et al 2011 Plasma Proc. Polym . 8 867) shows that scaling up was carried out successfully and holds promise for larger scale applications.

To face the worldwide problem of anthropogenic carbon dioxide (CO2) emission new techniques have to be developed. One approach for carbon capture utilization (CCU) is the conversion of CO2 to more valuable chemicals, e.g., carbon monoxide (CO) by means of non-thermal plasma generated at ambient conditions and supplied by excess energy from renewable sources. This paper reports about the effect of the admixture of inert gases, namely nitrogen or argon to CO2 in a coplanar dielectric barrier discharge (DBD). Systematic experiments were conducted to investigate the effects of applied voltage, frequency, flowrate and CO2 concentration in the influent. The composition of products, energy efficiency and yield were determined. Within the investigated parameter ranges, the maximum conversion of CO2 to CO efficiency of 1% was achieved when the specific input energy was 190 J L-1, whereas the maximum CO yield of 0.7% was achieved when the specific input energy was 210 J L-1. In conclusion, the energy efficiency can be significantly increased by operating the plasma in a diluted CO2 gas.