Investigation of methane plasmalysis in a nanosecond pulsed plasma reactor

Methane (CH₄) pyrolysis driven by electric energy in the form of plasma represents a powerful valorization strategy that could lead to reducing the emissions of a potent greenhouse gas. Nanosecond pulsed discharge (NPD) plasma is particularly effective in delivering high-energy and short pulses to the gas feedstock. Thereby, by controlling the specific energy input (SEI) to the pure CH₄ feed stream, conversion levels above 80% can be attained. Acetylene (C₂H₂) and hydrogen (H₂) are the main reaction products and are produced with individual selectivity above 70%. Hence, H₂ energy cost can be as low as 35 kWh/kg, which matches the thermodynamic limit of water electrolysis, and is close to high-temperature plasma set-ups. Besides, an energy conversion efficiency (ECE) of 57% is obtained by accounting for all the gas products, indicating effective transformation of discharge energy into chemical energy.