Ni-CeO2 nanocomposite with enhanced metal-support interaction for effective ammonia decomposition to hydrogen

Abstract

Ammonia is a promising hydrogen storage material due to its ease of storage and decomposition to COx-free hydrogen. Herein, we report colloidal solution combustion synthesis (CSCS) to construct Ni-CeO2 nanocomposite catalysts for efficient ammonia decomposition to generate hydrogen. Unlike conventional supported Ni/CeO2 catalyst, the prepared Ni-CeO2 nanocomposite catalyst exhibited nickel embedded in CeO2 matrix with enhanced metal-support interaction. The physicochemical properties and metal-support interaction of the catalysts can be tuned by adjusting the amount of silica sol template. The resulted Ni-CeO2 nanocomposite catalysts exhibited outstanding catalytic performance in terms of activity and stability. The hydrogen production rate reached 32.9 mmol gcat−1 min−1 at 500 °C, which is superior to other state-of-the-art Ni-based catalysts and even comparable or better than some reported Ru-based catalysts. The systematic characterizations demonstrated that the unique Ni-CeO2 nanocomposite structure with enhanced metal-support interaction, not only provided a rich Ni-CeO2 interface to stabilize small-sized Ni nanoparticles, but also had a high concentration of oxygen vacancy to strengthen electronic metal-support interaction, making nickel surface electron-rich. The integrated studies of kinetics, temperature-programmed surface reaction, and DFT calculations corroborated that this enhanced metal-support interaction including geometric and electronic effects, favored the enrichment of NH3 on the catalyst surface and facilitated rate-determining N≡N bond formation step, thereby boosting the reaction rate. This study highlights the importance of designing new structural catalysts with enhanced metal-support interaction for boosting hydrogen production from ammonia decomposition.