Decomposition of ammonia by atmospheric pressure AC discharge: Catalytic effect of the electrodes

Abstract

An atmospheric pressure AC discharge reactor with nickel (Ni), stainless steel (SS) and copper (Cu) tube electrodes has been systematically studied for ammonia decomposition. Ammonia conversion increased in the following order: Cu<SS<Ni. Conversion induction period was observed for both Ni and SS electrode reactors. The changes of the ammonia conversion, caused by the cover of the external surface of the Ni, SS and Cu electrodes with quartz tubes and the replacement of the Ni electrode and SS electrode by Cu electrode, suggested that the Cu electrode was inert, whereas the Ni and SS electrodes were all active catalysts and the catalytic conversion of ammonia on the catalytic electrodes contributed approximately 50% to the total ammonia decomposed, in which the high-voltage electrodes showed higher activity than the ground electrodes. The combinations of the pre- and post-treatments of the electrodes with the characterizations of the electrodes showed that Fe, Ni and their nitrides were the active phases for the catalytic decomposition of ammonia. Comparatively, the nitrides of Fe and Ni had better catalytic activity. The ammonia conversion induction of the SS and Ni electrode reactors was the in situ nitridation process of the SS and Ni electrodes in nature.