A competitive coordination strategy to synthesize Co3O4@carbon flower-like structures for high-performance asymmetric supercapacitors

2D nanosheets are attractive for energy conversion and storage because of their scale-dependent physical and chemical properties. However, nanosheets synthesized by liquid-phase method are easy to stack and it is difficult to obtain nanosheets with uniform dispersion and thickness. Here, a new strategy was developed to obtain uniformly dispersed 2D nanosheets. The regular dodecahedron structured ZIF-67 was employed as templates and NH4F was adopted as competitive units. 2D nanosheets of coordination polymers were induced vertically grow from the surface of ZIF-67, which effectively avoiding the stack of nanosheets. After carbonization, the obtained composites of Co3O4@carbon retained their original structure. The composites show excellent characteristics as the electrode of a supercapacitor. The capacitance of the NS-Co3O4@PC electrode is 940 F g(-1) at a current density of 1 A g(-1) , which is about 7 times than that of composite which derived from ZIF-67 under the same conditions. The most important is that the rate performance and cycling life were also improved as the result of hierarchical porous structure and good structure robustness. The method developed here may open up a novel and innovative approach to manipulate the structure of classical MOFs to obtain 2D nanosheets for a wealth of breakthrough applications.