Mechanistic Insights into Plasma-Thermal Field Coupling over Ru/CeO 2 for Enhanced Ammonia Decomposition

Abstract

Ammonia-hydrogen energy conversion is perceived as one of the effective methods to solve the storage and transportation problems of hydrogen energy. In recent years, the plasma-assisted strategy has shown great potential in the field of low-temperature ammonia decomposition. However, its enhancement mechanism for reaction kinetics has rarely been studied. Herein, by comparing the morphology and structural changes of catalysts with and without plasma field assistance before and after the reaction, we investigate the influence mechanism of the plasma field on the kinetics of the ammonia decomposition reaction (ADR). We found that the bombardment effect of high-energy particles in the plasma field can not only excite the reactant NH 3 to the activated NH x radical, but also effectively inhibit the agglomeration of active metal Ru in the catalyst, induce the generation of oxygen vacancies and N-containing carriers on the surface of CeO 2 , and thus change the dissociation path of N ≡ N. Ultimately, under the synergistic effect of the plasma and the catalyst, the low-temperature activity of the catalyst is significantly improved. At 350 ℃, the ammonia conversion rate of the plasma-assisted catalyst (Ru/CeO 2 -PEA) reaches 71%, which is much higher than 35% of the thermocatalytic sample without plasma field assistance, and the equilibrium state of ammonia decomposition can be reached at 450 ℃. This work sets out to elucidate the mechanistic details of plasma-assisted ammonia decomposition by establishing an improved theoretical model.