One-pot Preparation and the Electrochemical Properties of the composite NiCo Bimetallic Organic Framework and Carbon Quantum Dots

Designing metal-organic framework (MOF) materials with high conductivity is crucial for their application in energy storage devices. In this study, a simple process, namely, one-pot hydrothermal method was used for simultaneously synthesizing the composite of carbon quantum dots (CQD) and NiCo-MOF, and the effect of various carbon sources for CQD was compared. The results showed that it was very necessary to choose appropriate carbon source for obtaining NiCo-MOF with the expected lower Rs and Rct. Carbon sources significantly affected the morphology of NiCo-MOF, and in turn its specific surface area, pore volume and pore size. Particularly, after introducing CQD derived from citric acid, the electron cloud density around metal Co atom in NiCo-MOF composite became higher, improving electron transfer ability, activating the metal center Co and alleviating the polarization. As the result, the obtained NiCo-MOF-CA composite exhibited a capacitance of 1826.8 F g-1 at 1 A g-1, significantly higher than that of NiCo-MOF (1060.3 F g-1). An amplifying circuit model was proposed for explaining the phenomenon. Its cyclic performance also became better, but still left to be further improved. The simple synthesis process might be applied to preparing other similar composites. In addition, the conductivity of MOF was improved by introducing specific conductive additive to alter the electron structure of metal atom in active materials, providing an effective strategy for other researchers.