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

Abstract

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.