Ammonia decomposition over low-loading ruthenium catalyst achieved through “adiabatic” plasma reactor†

Abstract

Electrified catalytic processes for ammonia (NH₃) decomposition have been considered as essential technologies for distributed CO_x-free hydrogen production. Here we show that efficient NH₃ decomposition can be achieved over low-loading Ru/Al₂O₃ using an adiabatic dielectric barrier discharge (DBD) plasma reactor. Specifically, we demonstrate that the activity of NH₃ decomposition in the adiabatic plasma reactor is up to 4.9 times higher than that under nonadiabatic conditions. The NH₃ conversion was 73% (in the adiabatic plasma reactor) over the 0.05 wt% Ru/Al₂O₃ catalysts at a plasma power of 19 W, whereas, the conversion is only 15% when performed in the nonadiabatic plasma reactor, moreover, the catalyst was almost inactive in the thermal catalytic NH₃ decomposition. Additionally, nearly 100% NH₃ conversion was achieved over the 0.5 wt% Ru/Al₂O₃ catalyst at 19 W or over higher Ru loading catalysts at lower powers. We suggested that more efficient NH₃ decomposition was attributed to the enhanced synergy between plasma-activated radicals ·NH_x and vibrationally excited NH^v₃, and the catalytically active Ru sites when using the adiabatic plasma reactor – in contrast to the nonadiabatic counterpart.