Catalytic decomposition of ammonia to COx-free hydrogen over Ni/ZSM-5 catalysts: A comparative study of the preparation methods

A series of Ni/ZSM-5 catalysts are prepared by the methods of wet impregnation (IM), deposition-precipitation (DP), solid state ion exchange (SSIE), and modified solid state ion exchange (MSSIE), and used for catalytic decomposition of ammonia to COx-free hydrogen. Their physicochemical properties are characterized by XRD, N2 sorption, TEM, NH3-TPD, H2-TPR, solid-state NMR, and XPS techniques. It is revealed that the preparation methods could obviously influence the Ni species and catalytic performance of Ni/ZSM-5 catalysts, and the catalyst prepared by MSSIE method exhibits the best catalytic activity due to the presence of strong metal-support interaction between highly dispersed Ni nanoparticles and ZSM-5 support. The stability testing results showed almost no activity loss over Ni/ZSM-5(MSSIE) catalyst at 650 °C for 60 h, indicating a very promising catalyst for ammonia decomposition.