Construction of CuO/PPy heterojunction nanowire arrays on copper foam as integrated binder-free electrode material for high-performance supercapacitor

Abstract

Herein, we report a synthesis of 3D CuO/PPy heterojunction nanowire arrays formed on Cu foam via anodizing and electropolymerization. The prepared electrode shows superior performance as a supercapacitor electrode. The CuO NAs are vertically grown on the 3D Cu foam with a diameter of about 200 nm and uniformly coated by conductive polypyrrole (PPy) nanosheets with a length of about 40 nm. The electrodeposition time of PPy also affects the morphology of the material and influences the material's electrochemical properties. The experimental electrochemical results indicate that the CuO/PPy NAs-600 electrode, the optimum electrodeposition time for PPy, could achieve an excellent real-capacitance of 1080 mF cm−2 (675 F g−1) at a current density of 2 mA cm−2. Surprisingly, even at the current density of 20 mA cm−2, the actual capacitance still has 880 mF cm−2, and it could reach 103.57% of the original capacitance after 8000 cycles. Besides, an asymmetric supercapacitor (ASC) using CuO/PPy NAs-600 as positive electrode and activated carbon (AC) as negative electrode can provide an energy density of 0.93 mWh cm−2 at a power density of 1.71 mW cm−2 at a current density of 2 mA cm−2. Furthermore, a 1.8 V LED is lighted for 2 min by three ASC in series. Benefiting from the 3D heterojunction nanowire array structures and the good electronic conductivity between CuO, PPy and Cu foam substrate, the CuO/PPy NAs electrode has potential applications in capacitive energy storage.