Hydrogen generation by dielectric barrier discharge plasma assisted ammonia decomposition

Abstract

Ammonia, which can serve as a hydrogen carrier for later dehydrogenation in zero-carbon hydrogen generation, is considered one of the key solutions. However, this solution is challenged by the high decomposition temperature and low reaction efficiency. In this paper, non-equilibrium plasma was used to effectively improve the reaction performance of ammonia decomposition to hydrogen and nitrogen using a dielectric barrier discharge reactor. Impacts of operating conditions including discharge parameters, diluted gases, and ammonia concentration on hydrogen generation were investigated. The ammonia decomposition breakdown voltage followed the order of 1 % ammonia/carbon dioxide (4000 V) > 1 % ammonia/nitrogen (3500 V) > 1 % ammonia/helium (1500 V) ≈ 1 % ammonia/argon (1500 V). The effect of pulse voltage and frequency is more significant on plasma-assisted ammonia decomposition compared to the pulse width. When the pulse frequency and width were 30 kHz and 100 ns at 298 K, the ammonia conversion reached 26.3 %, 34.1 % and 40.9 % at 5000, 7000, and 10000 V, respectively. With the addition of argon in 5 % ammonia/helium, the resulting penning effect makes the discharge easier and more uniform to promote ammonia decomposition. Furthermore, the kinetic analysis was investigated to better understand the conversion and utilization of ammonia in plasma-assisted reactions.