Co/CoO nanoparticles loaded on multi-walled carbon Nanotubes@Covalent organic frameworks for electrocatalytic hydrogen evolution

Abstract

Producing hydrogen by electrolyzing water has received increased attention. Nevertheless, a major challenge remains in the search for high performance hydrogen evolution reaction (HER) electrocatalysts. In this work, multi-walled carbon nanotubes (MWCNTs) capped by TpPa covalent organic framework (TpPa-COF) react with cobalt nitrate hexahydrate (Co(NO3)2·6H2O) to form a novel ternary one-body complex (MWCNTs@TpPa-COF@Co/CoO). Wherein, TpPa-COF is constructed from 2,4,6-Triformylphloroglucinol (Tp) and p-phenylenediamine (Pa) as structural units. This COF is relatively inexpensive, provides more coordination sites for metal loading, and is particularly stable in acidic and basic media. The results show that the composite material has high electrocatalytic HER activity in a potassium hydroxide (KOH) condition with an overpotential value of 28.8 mV and a Tafel slope of 69.07 mV dec−1 at a current density of 10 mA cm−2. Meanwhile, the MWCNTs@TpPa-COF@Co/CoO showed excellent stability after 2000 cycles in alkaline media. The characterization demonstrated that the material provided low resistance during the charge transfer process, which resulted in improved electrochemical performance. In addition, the COF loaded with cobalt nanoparticles provided more active sites for the reaction. Thus, the synthesized MWCNTs@TpPa-COF@Co/CoO emerges turns out to be a Pt-free, stable and efficient HER electrocatalyst, holding significant promise for practical applications.