A non-Equilibrium Atmospheric Pressure Capacitively-Coupled-Plasma (CCP) driven at VHF (162MHz) for Plasma Catalysis of CO2 into CO

Abstract The design of a Very-High-Frequency (VHF) 162 MHz driven atmospheric-pressure Capacitively-Coupled-Plasma (CCP), with top and bottom electrodes operated in push-pull configuration, powered via a Power-Splitting-Transmission-Line-Driver (PSTLD), is presented. Application to the reprocessing of carbon dioxide into carbon-monoxide in this high” VHF atmospheric plasma is presented, demonstrating some behaviour of the plasma source. rf  power in the system is characterized using measured current (∼ 1′s Amps peak) and voltage (∼ 10′s Volts peak) waveforms at the electrode; Both are sinusoidal confirming a glow-discharge operational condition. Analysis of Optical Emission Spectra results find a highly non-equilibrium plasma, with high vibrational temperatures (from N2) in the range ∼4000 K, while gas temperature, monitored by a thermocouple at the gas outlet, remains low ∼300 K, and confirmed by analysis of the N2 rotational bands. The relative density of CO produced, as a by-product of CO2 dissociation, is measured optically using N2 as an actinometer. The CO density increases with rf  power and longer gas residence times in the plasma volume. The high VHF atmospheric plasma is found to operate in pure CO2 flows (no helium) with minimal gas heating for the full range of power densities (specific energy input of 0.4 to 2 eV per molecule) investigated.