Confined Ru Sites in a 13X Zeolite for Ultrahigh H₂ Production from NH₃ Decomposition

Abstract

High Resolution Image Download MS PowerPoint Slide Catalytic NH 3 synthesis and decomposition offer a new promising way to store and transport renewable energy in the form of NH 3 from remote or offshore sites to industrial plants. To use NH 3 as a hydrogen carrier, it is important to understand the catalytic functionality of NH 3 decomposition reactions at an atomic level. Here, we report for the first time that Ru species confined in a 13X zeolite cavity display the highest specific catalytic activity of over 4000 h –1 for the NH 3 decomposition with a lower activation barrier, compared to most reported catalytic materials in the literature. Mechanistic and modeling studies clearly indicate that the N–H bond of NH 3 is ruptured heterolytically by the frustrated Lewis pair of Ru δ+ –O δ− in the zeolite identified by synchrotron X-rays and neutron powder diffraction with Rietveld refinement as well as other characterization techniques including solid-state nuclear magnetic resonance spectroscopy, in situ diffuse reflectance infrared transform spectroscopy, and temperature-programmed analysis. This contrasts with the homolytic cleavage of N–H displayed by metal nanoparticles. Our work reveals the unprecedented unique behavior of cooperative frustrated Lewis pairs created by the metal species on the internal zeolite surface, resulting in a dynamic hydrogen shuttling from NH 3 to regenerate framework Brønsted acid sites that eventually are converted to molecular hydrogen.