According to a first aspect of the present invention, there is provided an apparatus for forming NOx from nitrogen and oxygen, the apparatus comprising: a gliding arc discharge, GAD, device arranged to generate a plasma; a passageway including an inlet for a feed gas comprising nitrogen and oxygen and an outlet for the NO.sub.x, wherein the passageway extends, at least in part, through the GAD device wherein, in use, the nitrogen and oxygen are reacted in the generated plasma, thereby forming the NO.sub.x from at least some of the nitrogen and oxygen; and a post-discharge container for adjusting the NO.sub.2/NO ratio in the formed NO.sub.x to from 1:2 to 2:1.

The present invention concerns the fabrication of large graphene electrodes. In the electrolysis of water or in the operation of a hydrogen fuel cell. the electrical conductivity is important to reduce the energy consumption. Titanium electrodes are widely used but their conductivity is only about 4% of copper. Graphene is 70% more conductive than copper and is chemically stable provided there are no metal ions in the electrolyte. By irradiating a mixture of carbon dioxide gas and hydrogen gas quantities of graphene can readily be produced which can then be manufactured into large electrodes by way of the described press formation.