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 similar to 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).