A Co/Cu-based bimetallic metal organic framework for high performance hybrid supercapacitors

Introducing a second metal ion into the monometallic metal organic frameworks (MOFs) is considered as an effective method to improve the energy storage performance of monometallic MOFs. Herein, a Co/Cu bimetallic metal organic framework was successfully prepared by a facile hydrothermal crystallization method. Interestingly, the Co/Cu MOF composite displays unique morphology composed of special spherical structure and the lamellar structure, which is significantly different from the small lamellar structure of Cu MOF and the large lamellar structure of Co MOF. More interestingly, the Co/Cu MOF exhibits a high specific capacity of 70.7 m Ah g−1 (462. 7 F g−1) at 1 A g−1 when the electrolyte is 1 M KOH solution, which is significantly higher than that of the monometallic metal–organic frameworks of Co and Cu. The composite still gives excellent rate capacity at high current density (76 % capacitance retention at 10 A g−1) and cycling performance (capacitance remains at 71 % after 5000 cycles). The reason for the excellent energy storage of Co/Cu MOF would be attributed to the unique morphology and excellent conductivity. Moreover, the asymmetric device was constructed with activated carbon (AC) as the negative electrode and Co/Cu MOF as the positive electrode. The device provides an energy density of 47.08 W h kg−1 when the power density is 750 W kg−1.