Direct plasma conversion of liquid methanol provides a compact route for producing hydrogen-rich gas, but discharge development in liquids is strongly affected by electrode geometry and transient gas-channel formation. In conventional fixed-gap configurations, increasing the electrode spacing may enlarge the available reaction region while simultaneously reducing breakdown reliability and discharge continuity. In this work, a liquid phase gliding arc (LGA) configuration with upward-diverging electrodes was investigated as a strategy to spatially extend the discharge without sacrificing its stability. The LGA reactor was compared with needle-to-needle configurations having electrode gaps of 4, 8, 16, and 32 mm under comparable time-averaged discharge powers of approximately 320 W. High-speed imaging, synchronized voltage-current measurements, electrostatic simulation, optical emission spectroscopy, and gas chromatography were employed to correlate electrode geometry with discharge dynamics and methanol conversion. Fixed-gap needle discharges remained relatively stable at small gaps but were confined to localized regions near the electrode tips. Increasing the gap to 16 mm resulted in strongly intermittent operation, with the plasma duty cycle decreasing to approximately 25%, whereas breakdown could not be sustained at 32 mm. In contrast, the diverging-electrode configuration enabled the discharge channel to initiate at the narrow lower gap and subsequently glide upward, maintaining a near-continuous discharge while expanding the average projected plasma area to above 50 mm². This extended discharge region produced more than 2.4 L/min of H₂, with the gaseous products consisting mainly of approximately 65 vol.% H₂ and 33 vol.% CO. The specific electrical energy consumption for H₂ production reached approximately 2.2 kWh/m³, corresponding to an H₂ mass productivity of 39.9 g/kWh. Meanwhile, electrode mass loss was reduced from more than 50 mg for the 4 mm needle configuration to approximately 5 mg for the LGA because the moving arc distributed the thermal load over a larger electrode surface. These results indicate that guiding the spatial motion of the discharge is more effective than simply increasing a fixed electrode gap for enlarging the active plasma region, providing a practical design concept for stable liquid-phase plasma reactors used in electrically driven fuel conversion and hydrogen-rich syngas production.
 

Liquid phase plasma,Gliding arc discharge,Electrode geometry,Methanol conversion,Hydrogen-rich syngas