Cobalt–carbon derived from zeolitic imidazolate framework on Ni foam as high-performance supercapacitor electrode material

Highlights: • Co(MeIM)₂ (MeIM = 2-methy-limidazole) was chosen as precursor to synthesize the cobalt/carbon composites. • Co(MeIM)₂ (MeIM = 2-methy-limidazole) grew on the Ni foam directly and intimately. • The obtained cobalt nanoparticles are 2–3 nm in size and anchored on carbon homogeneously. • The specific capacitance of the composites is up to 512 F g⁻¹ at current density of 1 A g⁻¹. - Abstract: ZIF-67 (Co(MeIM)₂, MeIM = 2-methylimidazole) was selected as a precursor to synthesize the metallic cobalt/carbon composites on Ni foam directly and intimately. The results show that ZIF-67 forms a uniform membrane and densely covers the Ni foam substrate. Besides, the cobalt/carbon composites obtained are composed of cobalt nanoparticles with a diameter up to around 2.6 nm, which are anchored on carbon homogeneously. The specific capacitance of the composites material is up to 512 F g⁻¹ at a current density of 1 A g⁻¹ in 1.0 M KOH electrolyte. Furthermore, the specific capacitance loss is ∼46.4% with increase at the current density from 1 to 20 A g⁻¹. More significantly, the specific capacitance retention rate is 87.5% at a current density of 5 A g⁻¹ after 1000 cycles. These results suggest that the electrochemical performance can be greatly enhanced by the well-controlled size and distribution of the cobalt nanoparticles, which is mainly attributed to the unique structure and composition of ZIF-67.