Covalent triazine-based framework as an efficient catalyst support for ammonia decomposition

Abstract

The covalent triazine-based framework (CTF), a new type of nitrogen-containing microporous polymer, was employed as a catalyst support for ammonia decomposition. Either in terms of NH₃ conversion rate or turnover frequency, Ru/CTF-1 has a highly enhanced performance compared to Ru/CNTs, which rank as one of the best un-promoted catalysts reported so far. The compositional and structural information of Ru/CTF-1 and Ru/CNTs catalysts have been characterized by ICP, N₂ physisorption, XRD, TEM, XPS, and NH₃-TPD techniques. Ru particles on CTF-1 and CNTs are ca. 3 nm in diameter and have a similar degree of dispersion. However, the binding energy of Ru 3p electrons is ca. 0.6 eV less for Ru/CTF-1 than that for Ru/CNTs showing significant increase in electron density in the former, which is likely due to the interaction between the nitrogen-rich groups of CTF-1 and the Ru nanoparticles. Moreover, the presence of CTF-1 enhances the chemisorption of NH₃, which, together with the increased electron density of Ru, may facilitate the competitive chemisorption of NH₃ and recombinative desorption of adsorbed nitrogen via lowered activation energy and thus, enable faster reaction rate.