Cobalt nanoparticles packaged into nitrogen-doped porous carbon derived from metal-organic framework nanocrystals for hydrogen production by hydrolysis of sodium borohydride

Abstract

Efficient safe transportation and generation of hydrogen are the key technologies for the hydrogen economy development in future. Sodium borohydride (NaBH4) features highly volumetric density and environmentally benign hydrolysis products, which making it a promising candidate for chemical hydrogen storage. Cobalt nanoparticles packaged into nitrogen-doped porous carbon were successfully prepared by pyrolysis of MOFs. The addition of Zn in MOFs as a “fence” expanded the distance of adjacent Co atoms in space and simultaneously, the leaving Zn2+ sites generated free N sites during pyrolysis. These are beneficial to reduce the sizes of Co nanoparticles and enhance the dispersity of active sites. The modification method allows the cobalt nanoparticles to be uniformly and finely confined within the porous carbon. Contributed by highly dispersed Co nanoparticles and confinement effect, the catalyst showed excellent catalytic activity with hydrogen production rate of 1807 mL (H2) min−1·gCo−1 and lower activation energy (20 kJ/mol) than ever reported. The stability test confirmed that deactivation of catalyst occurred due to deposition of borate species at the surface of catalyst. This observation may provide an idea to modify and upgrade stability of catalyst.