Hierarchical porous cobalt nanoparticles encapsulated in heteroatom-doped hollow carbon as an enhancing multifunctional catalyst for hydrolysis of sodium borohydride and hydrogenation of bromate in water

Abstract

Multifunctional heterogeneous catalysts have been consistently explored in recent years because of their distinctive catalytic activity in different catalysis areas at once. Here, a cobalt (Co) nanoparticles encapsulated in nitrogen-doped hollow carbon (denoted as Co@NHC) is prepared by two-step modifications of acid etching and high temperature carbonization in the inert atmosphere using a peculiar polyhedral configuration Co-ZIF as an initial template. Benefiting from an intriguing polyhedral configuration hollow structure with high specific surface area and pore volume supplying plentiful active sites, Co@NHC shows exceptional catalytic activity in catalyzing hydrolysis of NaBH4 and hydrogenation of toxic bromate in water. From experimental results, Co@NHC could efficiently enhance the generation of H2 with a H2 generation rate of 1515.4 mL min−1 gcat−1 meanwhile the activation energy (Ea) calculated from Co@NHC/NaBH4 system was only 12.6 kJ mol−1. Besides, the combination of Co@NHC and NaBH4 could further reduce toxic bromate ions into bromide via catalytic hydrogenation with a maximum bromate removal capacity of 390.6 μmol g−1. More importantly, due to its strong magnetization, Co@NHC could be simply recovered after reactions, making it well-preserve the unique structure as well as catalytic activity for multiple continuous recycles in both catalytic applications. Additionally, the plausible reaction mechanisms in catalyzing hydrolysis of NaBH4 and hydrogenation of bromate were also proposed. This work has pioneered a promising approach on preparing an engrossing magnetic heterogeneous Co-based catalyst that is practically applicable in various areas of catalysis.