Rational design of CuO nanostructures grown on carbon fiber fabrics with enhanced electrochemical performance for flexible supercapacitor

It is known that Faradaic redox reactions take place on the surface or inside of materials through ion insertion/extraction on the surface. Therefore, rational design of nanostructures to enlarge the specific surface of electrode materials is an effective way to achieve desirable electrochemical performance. In this paper, three kinds of copper oxide structures, including flower-like, particle-like and coral-like arrays grown on the carbon fiber fabrics, are prepared by the hydrothermal method under different conditions. These flowers, particles and corals are further assembled by nanoscale sheets, rods and porous networks, respectively. The flexible solid-state symmetric supercapacitor based on two electrodes of these CuO nanostructures is fabricated, and the electrochemical properties of these CuO nanostructures are investigated, from which we find that the supercapacitor based on the coral-like CuO nanostructure presents better performance than that of particle-like and flower-like CuO due to its higher specific area and suitable pores with rich reaction sites and ion diffusion channels. The specific capacitances of the flower-like, particle-like and coral-like CuO are 164.50, 309.65 and 481.76 F g⁻¹, respectively, at scan rate of 5 mV s⁻¹. The specific capacitance of the coral-like nanostructure keeps 86.45% after 2000 cycles. These results indicate that the morphology influences the electrochemical properties greatly. Three supercapactiors connected in series can light up ten LEDs for 600 s.