Optical emission spectroscopy measurement of plasma parameters in a nanosecond pulsed spark discharge for CO2/CH4 dry reforming.

In this paper, a nanosecond pulsed spark discharge in CO2/CH4 mixture gas at atmospheric pressure is studied with optical emission spectroscopy. A high-voltage pulse is applied across two plate-shaped electrodes at a repetition frequency of 1 kHz. Emphatically, plasma parameters of this discharge are estimated by spectroscopic methods for giving an insight into the underlying dry reforming reaction mechanism. The time-averaged optical emission is mainly caused by atomic spectral lines of excited O, H, and C+, and C2 swan bands. The vibrational temperature of 8500 ± 50 K and rotational temperature of 3200 ± 100 K are estimated by the excited C2 molecules, respectively. The electron density is calculated by Stark broadening of O (844.6 nm), Hα (656.3 nm), and Hβ (486.1 nm) for 3.4 ∼ 7.71 × 1017 cm-3 while C+ (723.6 nm) for 4.37 × 1018 cm-3 with an electron excitation temperature of 0.58 eV that is estimated by the intensity ratio of Hα and Hβ. The determination of plasma parameters offers essential data for subsequent reaction kinetics research of the plasma-assisted dry reforming of CH4.