Highly Efficient and Selective Co@ZIF-8 Nanocatalyst for Hydrogen Release from Sodium Borohydride Hydrolysis

Sodium borohydride hydrolysis catalyzed by composite nano-materials has long been proposed as a viable possibility for hydrogen generation, but it required either expensive noble metals or sophisticated composites. Herein, the catalysis of NaBH4 hydrolysis is studied with single earth-abundant Fe, Co, Ni, and Cu nanoparticles supported by a metal organic framework (MOF), ZIF-8. It appears that CoNPs@ZIF-8 is the most efficient and selective catalyst in this series. The turnover frequency (TOF) related to the total atoms number within the cobalt nanoparticles reaches 14000 mL(H2)min(-1) g(Co)(-1) at 30 degrees C, and the TOF(s) related to the number of surface atoms of the cobalt nanoparticles 19400 mL(H2)min(-1) g(Co)(-1) at 30 degrees C. Kinetic studies including a high kinetic isotope effect disclosed using D2O (k(H)/k(D)=6.85) and the favorable effect of NaOH lead to the suggestion of an oxidative addition of a O-H bond of water in the rate-determining step.