Cu/CuxO@C nanocomposites as efficient electrodes for high-performance supercapacitor devices

Abstract

A novel method, reduction followed by oxidation procedure, has been developed to fabricate efficient electrodes derived from metal–organic frameworks (MOFs), which were synthesized using terephthalic acid (TP) and 1,3,5-benzenetricarboxylic acid (BTC) as organic ligands. The copper-based composites, namely Cu/Cu_xO@C (x = 1 and 2), were obtained through two steps: first calcining the precursors at high temperature under a nitrogen atmosphere, and then calcining in air to increase the number of porous active sites. For a more convenient description, the calcined materials are denoted as 800-TP, 900-TP, 800-BTC and 900-BTC, respectively, according to the calcination temperature and the corresponding organic ligand. Their electrochemical performances in supercapacitors (SCs) suggest that a higher calcination temperature endows the as-resultant materials with a larger specific surface area, higher carbon content, higher electrical conductivity, and better ion transport ability. For example, the 900-BTC electrode delivers a specific capacity of 400 C g⁻¹ at a current density of 3 A g⁻¹ under a three-electrode configuration. Even under a double-electrode system, the corresponding 900-BTC//AC device (AC represents activated carbon) also achieves superior electrochemical performance with an energy density of 24.02 W h kg⁻¹ at a power density of 825 W kg⁻¹ and the specific capacitance retention rate for the device is maintained at 91.7% after 3000 unceasing loops, indicating its potential for practical applications.