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

Catalytic NH3 synthesis and decompositionoffer a newpromising way to store and transport renewable energy in the formof NH3 from remote or offshore sites to industrial plants.To use NH3 as a hydrogen carrier, it is important to understandthe catalytic functionality of NH3 decomposition reactionsat an atomic level. Here, we report for the first time that Ru speciesconfined in a 13X zeolite cavity display the highest specific catalyticactivity of over 4000 h(-1) for the NH3 decomposition with a lower activation barrier, compared to mostreported catalytic materials in the literature. Mechanistic and modelingstudies clearly indicate that the N-H bond of NH3 is ruptured heterolytically by the frustrated Lewis pair of Ru & delta;+-O & delta;- in the zeoliteidentified by synchrotron X-rays and neutron powder diffraction withRietveld refinement as well as other characterization techniques includingsolid-state nuclear magnetic resonance spectroscopy, in situ diffusereflectance infrared transform spectroscopy, and temperature-programmedanalysis. This contrasts with the homolytic cleavage of N-Hdisplayed by metal nanoparticles. Our work reveals the unprecedentedunique behavior of cooperative frustrated Lewis pairs created by themetal species on the internal zeolite surface, resulting in a dynamichydrogen shuttling from NH3 to regenerate framework Bronstedacid sites that eventually are converted to molecular hydrogen.