Copper nanocrystal modified activated carbon for supercapacitors with enhanced volumetric energy and power density

Copper nanocrystals homogeneously dispersed in activated carbon (AC) were synthesized by an in situ solution-based absorption–reduction method, and the resulting composites were characterized and studied for supercapacitor application. The effects of copper nanocrystals and their content on the electrochemical properties of the obtained AC composites were investigated using multiple techniques, including X-ray photoelectron spectroscopy, nitrogen sorption analysis, cyclic voltammetry, galvanic cycling, and electrochemical impedance spectroscopy. Results showed that the addition of copper nanocrystals in the AC composites has little effect on the surface area and porosity of AC, and is helpful to reduce its equivalent series resistance, which is favorable to achieve higher charge/discharge rate and improve its power density when used as electrodes for supercapacitors. Copper nanocrystals and the partially oxidized phase CuO act as pseudo-active materials and improve the capacity of the AC composite electrode. The volumetric capacity, energy density, and power density of copper nanocrystal modified activated carbon are much higher than those of AC and AC mechanically mixed with copper particles. Copper nanocrystal modified AC presents a high volumetric capacitance of 62 F cm−3, more than twice of that of unmodified AC.

► Cu modified activated carbon for supercapacitor was synthesized by in situ solution-based absorption–reduction method.
► The incorporation of copper nanocrystals in AC has little effect on the surface area and porosity of activated carbon.
► The incorporation of copper nanocrystals improves the electrical conductivity of the carbon network.
► The addition of Cu can greatly increase the volumetric capacitance and power density of AC.
► The effects of copper content on the electrochemical properties of AC were investigated.