Encapsulated cobalt nanoparticles as a recoverable catalyst for the hydrolysis of sodium borohydride

The significant challenges encountered when replacing precious-metal-based catalysts in the hydrolysis of sodium borohydride (NaBH4) are related to the low durability and efficiency of nonprecious metals. In this study, we synthesized nitrogen-doped mesoporous graphitic carbon encapsulated cobalt nanoparticles (Co@NMGC) with a core-shell structure by the carbonization of ethylenediaminetetraacetic acid (EDTA)-derived carbon. These structures were then used as catalysts for the hydrolisis of NaBH4. Among different calcination temperatures, 500 degrees C resulted in the best catalytic activity, with a hydrogen production rate of 3575 mL min(-1) g(-1) at 25 +/- 0.1 degrees C and low activation energy of 35.2 kJ mol(-1) for NaBH4 hydrolysis. The maximum hydrogen production rate using the cobalt-based complex catalyst was about three-fold that achieved using the pure cobalt catalyst. We found that the complex catalyst showed high durability, retaining 82.5% of the initial catalytic activity after 20 hydrolysis cycles. The catalyst was also magnetic, making it 100% recyclable. Density functional theory (DFT) calculations showed that the graphitic carbon shell promoted electron penetration from the Co nanoparticles into the graphitic carbon surface, which prevented oxidation of the Co nanoparticles, while the Co core provided better conductivity. This work provides a novel method for the synthesis of shelled-structure catalysts, which have potential applications in the hydrolysis of sodium borohydride.