Plasma-enhanced catalytic ammonia decomposition over ruthenium (Ru/Al2O3) and soda glass (SiO2) materials

Abstract

Catalytic ammonia (NH3) decomposition has been identified as a COx-free, sustainable hydrogen production method for fuel cell applications. In this study, the performance of plasma–catalyst-based NH3 decomposition over ruthenium (Ru/Al2O3) and soda glass (SiO2) catalytic materials at atmospheric pressure and ambient temperature was investigated. NH3 decomposition reactions were conducted in a dielectric barrier discharge plasma plate-type reactor. NH3 was fed into the plate catalytic microreactor at flow rates of 0.1–1 L/min and plasma voltages of 12–18 kV. Compared to plasma NH3 decomposition without a catalyst, plasma–catalyst-based NH3 decomposition showed a significant enhancement of the hydrogen production rate and energy efficiency. Furthermore, the hydrogen concentration results obtained over the Ru/Al2O3 catalyst were higher than those over the SiO2 catalyst because Ru/Al2O3 possesses good electronic properties and exhibits high sensitivity to NH3 decomposition. In addition, the resulting plasma heat enhanced the activation of the catalytic material, subsequently leading to an increase in the hydrogen production rate from NH3. The maximum conversion rates were 85.65% and 84.39% for Ru/Al2O3 and SiO2, respectively. Moreover, the energy efficiency of NH3 decomposition over the Ru-based catalyst material was higher than that over the SiO2 material. The presence of the catalyst active sites and plasma enhanced the mean electron energy, which could enhance the dissociation of NH3. It can be concluded that the SiO2 material can be utilised as a catalyst and that its combination with plasma accelerates the decomposition process of NH3 and incurs a lower cost compared to Ru materials.