Cu/Co mixed hierarchical tubular heterostructures for alkaline supercapacitors

Abstract

The hierarchical hollow structures of electrode materials s of supercapacitors is effective for the large specific surface area and fast ions and charge transports. Cu nanowires as self-engaged templates provide sites and paths for the nucleation and growth of the ZIF-67. Meanwhile, Cu atoms can disperse into metal organic frameworks (MOFs) to form Cu-Co mixed oxides and construct heterostructures. In this case, Cu nanowires are used as a template and an activated part to improve the internal electronic structures. The electrochemical performance can be improved due to these features. Herein, Cu nanowires and MOFs are combined via a mild and efficient approach to fabricate Cu-Co-O/CuO electrode materials. This electrode exhibits excellent electrochemical performance with a specific capacitance of 834.1 F g−1 at 1 A g−1. The assembled asymmetric supercapacitor (ASC) shows an ultra-high energy density of 40.7 W h kg−1 at a power density of 915 W kg−1 and a good capacitance retention after 8000 cycles in a 2 M KOH aqueous solution. The results otained in this work indicate a strategy of the combination of reactive metals with metal organic frameworks used as electrode materials for electrochemical supercapacitors.