Panpan Xu

One-step synthesis of copper compounds on copper foil and their supercapacitive performance

Nanowire-like Cu(OH)2 arrays, microflower-like CuO standing on Cu(OH)2 nanowires and hierarchical CuO microflowers are directly synthesized via a simple and cost-effective liquid–solid reaction. The specific capacitance of Cu(OH)2, CuO/Cu(OH)2 and CuO are 511.5, 78.44 and 30.36 F g−1, respectively, at a current density of 5 mA cm−2. Therefore, the Cu(OH)2/Cu-foil electrode displays the best supercapacitive performance. The capacitance retention reaches up to 83% after 5000 charge/discharge cycles with the columbic efficiency of ∼98%. More importantly, the nanowire Cu(OH)2 transformed into stable nanosheet CuO after about 600 constant current charge–discharge cycles. Additionally, we fabricate an asymmetric supercapacitor with nanowire Cu(OH)2/Cu-foil as a positive electrode, activated carbon (AC) as a negative electrode and 6 mol dm−3 KOH as electrolyte, which exhibits an energy density of 18.3 W h kg−1 at a power density of 326 W kg−1.

Preparation of porous cadmium sulphide on nickel foam: a novel electrode material with excellent supercapacitor performance

Large surface area, high electrical conductivity, and abundant channels have been recognized to favor faradic capacitors, but their realization at the same time by a facile preparation process is still a great challenge. Here, we synthesized porous cadmium sulphide freely standing on nickel foam (CdS/NF) via a one-step hydrothermal method which possesses high specific capacitance, good rate capability and outstanding cycling stability. The CdS/NF microspheres present pores with a mean size of ∼3 nm, resulting in fast diffusion of ions, facile transportation of electrons and high activity, which make great synergistic contributions to reversible redox reactions. In the resulting supercapacitors, a specific capacitance of 909 F g−1 is achieved at a current density of 2 mA cm−2 with excellent rate capability that 88% of the original capacitance is retained at 50 mA cm−2. After 5000 charge–discharge cycles at current densities as large as 50 mA cm−2, 104% of initial capacitance is maintained. Finally, asymmetric supercapacitors with a high energy density of 28 W h kg−1 at a power density of 160 W kg−1 were obtained.

Preparation of binder-free CuO/Cu2O/Cu composites: a novel electrode material for supercapacitor applications

Cuprous(I) oxide (Cu2O) carries high theoretical specific capacitance (2247.6 F g−1), however, the amount of research about the supercapacitive performance of Cu2O is relatively small compared with other transition metal oxides. A composite of metal and metal oxide could improve the electrochemical performance efficiently. In this work, the results of XRD and XPS demonstrate that CuO/Cu2O/Cu is prepared successfully via a facile, eco-friendly, one-step template-free growth process. SEM figures show that cubic CuO/Cu2O/Cu uniformly and densely covers a skeleton of nickel foam. The binder-free CuO/Cu2O/Cu electrode exhibits excellent supercapacitive performance with a high specific capacitance of 878 F g−1 at a current density of 5 mA cm−2 (1.67 A g−1), when the current density is enlarged ten times (50 mA cm−2 (16.7 A g−1)), the specific capacitance still remains at 545 F g−1. Furthermore, we have first successfully constructed a CuO/Cu2O/Cu//AC asymmetric supercapacitor, which can achieve an energy density of 42 W h kg−1 at a power density of 0.44 kW kg−1. The good electrochemical performance and simple accessibility prove that the as-prepared CuO/Cu2O/Cu/NF electrode has a potential application in electrochemical capacitors.