Improving the electrochemical performance of nickel-cobalt organic framework by hybridizing with carbon quantum dots

Abstract

To improve the electrochemical properties of nickel-cobalt metal-organic skeleton materials, two carbon quantum dots (CQDs), namely, CQD-CA and N-doped CQD-CAn, were prepared by using citric acid as carbon source and then introduced into NiCo-MOF to prepare CQDs/NiCo-MOF composites. Through the application of physical characterization and electrochemical analysis methods, such as SEM, TEM, XRD, XPS and BET, it was found that NiCo-MOF@CA and NiCo-MOF@CAn exhibited a nano thinner lamellar structure, higher specific surface area, larger pore structure, and excellent electron transport ability. Especially, by introducing CQDs, the charge could transfer from oxygen to Ni and Co, and there was some higher electron cloud density around active metals Ni and Co in NiCo-MOF@CAn than in NiCo-MOF, effectively activating the metal center Ni and Co. As the result, the specific capacitance of NiCo-MOF@CAn reached 1917.7 F·g⁻¹ at the potential scan rate 5 mV·s⁻¹, significantly higher than that of NiCo-MOF (1173.4 F·g⁻¹) and NiCo-MOF@CA (1489.3 F·g⁻¹). The method might provide an alternative strategy for modulating the morphology, porous structure and the partial electron structure of the target materials by introducing various CQDs.