Plasma synthesis of ammonia in a tangled wire dielectric barrier discharge reactor: Effect of electrode materials

Abstract

Plasma synthesis of NH3 from N2 and renewable H2 under mild conditions is very attractive for decentralised sustainable green ammonia production using intermittent renewables. In this study, NH3 synthesis was performed under ambient conditions in a dielectric barrier discharge (DBD) plasma reactor. Different tangled wire internal electrodes were employed to understand the influence of electrode materials on plasma ammonia synthesis. Compared with a rod electrode, a tangled wire electrode substantially enhanced the NH3 concentration and reduced the energy cost for ammonia production, which can be attributed to the expanded surface area and the chemisorption properties of the tangled electrodes. The influence of the N2/H2 molar ratio and total flow rate on the reaction performance was also evaluated. The lowest energy cost (59.0 MJ mol−1) for ammonia production was achieved using a Cu tangled electrode at a total flow rate of 250 ml min−1 and a discharge power of 20 W. The electrical diagnostics of the plasma process showed that the tangled wire electrodes decreased the breakdown voltage of the DBD and enhanced charge deposition, which enhanced the NH3 production. The reaction mechanism was discussed for the process optimisation of ammonia synthesis in a tangled wire DBD system.