Metal-organic framework ZIF-67 derived Co@CN catalysts for the promising generation of hydrogen from ammonia decomposition

Ammonia, a carbon-free hydrogen storage medium comprising up to 17.76 wt% hydrogen, presents considerable advantages for storage and transportation. However, challenges persist in terms of catalytic activity, stability, and process optimization for the effective generation of hydrogen through ammonia decomposition. To address these challenges, a series of Co-based catalysts coated with nitrogen-doped carbon (Co@CN), derived from the metal–organic framework ZIF-67, are synthesized and systematically evaluated for ammonia decomposition. The Co@CN-600 catalyst attains an impressive nearly 100 % ammonia decomposition with an H₂ production rate of 10 mmol H₂·g_cat.^{- 1}·min⁻¹ at a temperature of 550 °C and a gas hourly space velocity of 9,000 mL·g_cat. ^-1·h⁻¹ within the fixed-bed reactor, utilizing an optimized 10 mm reaction tube, aided by ANSYS Icepak simulation. The Co@CN-600 catalyst exhibits a lower activation energy of 79.40 kJ·mol⁻¹ and demonstrates a higher catalytic activity compared to reported Co-based catalysts, rivaling even that of Ru-based catalysts. In addition, the ZIF-67 derived Co@CN catalyst presents a long-term stability for ammonia decomposition. The uniform dispersion of Co nanoparticles within a nitrogen-doped carbon support featuring an optimized pore structure enhances the synergistic interaction between Co and N species. This facilitates the transfer of electrons from pyridine nitrogen to the cobalt species, thereby strengthening the adsorption activation of ammonia molecules on the Co active sites and augmenting catalytic activity. Additionally, the nitrogen-doped carbon support significantly improves the anchoring of Co nanoparticles, markedly enhancing stability. This work offers a design framework for the development of low-temperature, highly efficient non-precious metal catalysts for ammonia decomposition, thus providing innovative insights for low-carbon hydrogen production.