Effect of BaNH, CaNH, Mg3N2 on the activity of Co in NH3 decomposition catalysis

Development of active and non-noble metal-based catalyst for H-2 production via NH3 decomposition is crucial for the implementation of NH3 as a H-2 carrier. Co-based catalysts have received increasing attention because of its high intrinsic activity and moderate cost. In this work, we examined the effect of BaNH, CaNH and Mg3N2 on the catalytic activity of Co in the NH3 decomposition reaction. The H-2 formation rate ranks the order as Co-BaNH > Co-CaNH > Co-Mg3N2 approximate to Co/CNTs within a reaction temperature range of 300-550 degrees C. It is worth pointing out that the H-2 formation rate of Co-BaNH at 500 degrees C reaches 20 mmol(H2) g(cat)(-1) min(-1), which is comparable to those of the active Ru/Al2O3 (ca. 17 mmol(H2) g(cat)(-1) min(-1)) and Ru/AC (21 mmol(H2) g(cat)(-1) min(-1)) catalysts under the similar reaction conditions. In-depth research shows that Co-BaNH exhibits an obviously higher intrinsic activity and much lower E-a (46.2 kJ mol(-1)) than other Co-based catalysts, suggesting that BaNH may play a different role from CaNH, Mg3N2 and CNTs during the catalytic process. Combined results of XRD, Ar-TPD and XAS show that a [Co-N-Ba]-like intermediate species is likely formed at the interface of Co metal and BaNH, which may lead to a more energy-efficient reaction pathway than that of neat Co metal for NH3 decomposition. (C) 2019 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.