A non-thermal plasma reforming unit operating at atmospheric pressure has been developed for converting methane to COx-free hydrogen. Argon was used to provide additional electrons and photons for higher reaction rates. A series of experiments was performed for positive corona discharge at a fixed inter-electrode distance (15 mm) to study the effects of discharge power (range of 14-20 W) and residence time (60, 120, 180 and 240 s). A second series of experiments studied the effect of inter-electrode distance on hydrogen production, with distances of 15, 20, 25, 30 and 35 mm tested. The analysis of the results shows that both discharge power and residence time, have a positive influence on methane conversion, hydrogen selectivity and energy conversion efficiency. Longer discharge gaps favour hydrogen production. A final series of experiments on corona polarity showed that a positive discharge was preferable. (C) 2013 Elsevier Ltd. All rights reserved.