Reusable CoxNi1−x dye adsorbents as supercapacitor electrode materials

Abstract

Herein, a novel method was developed to synthesize a CoNi binary metal/Co–Ni oxide@carbon (M/MO@C-600) composite by sintering CoNi nanoparticles with Congo Red (CR) at 600 °C and under a N₂ atmosphere; this composite was then utilized to prepare electrode materials. Herein, C and O originated from the CR molecule. The M/MO@C-600 composite with a flaky structure delivered a capacitance of 1134.9 F g⁻¹ at 1 A g⁻¹ and a cycling stability with 66% retention even at the high current density of 10 A g⁻¹ after 2000 cycles. Furthermore, a simple asymmetric supercapacitor (ASC) was developed with the M/MO@C-600 composite as the positive electrode material and commercial activated carbon as the negative electrode material. A high specific capacitance of 111.2 F g⁻¹ (at 0.5 A g⁻¹) and excellent energy density of 44.6 W h kg⁻¹ (at 0.425 kW kg⁻¹) were obtained for the ASC device, and 100% capacitance was retained even after 10 000 cycles at 6 A g⁻¹. This method for the preparation of electrode materials may facilitate to simultaneously relieve the environmental and energy pressure.