pH based supercapacitors: Achieving high capacitance in gold metallized regenerated cellulose amide supercapacitor electrodes by pH gradient

Abstract

High energy density was achieved through pH gradient creation in an amidic cellulose incorporated with gold nanoparticles. Three different pH gradients (6–8, 4–10, and 2–12) showed respective specific capacitances of 218, 423 and 603 Fg−1 energy densities of 34, 67 and 96 WhKg −1. The pH gradient overpotential were 0.011, 0.014 and 0.020 V for the three respective pH gradients, where the electrode having the highest overpotential had the highest energy density. The electrode with a pH gradient of 2–12 had the lowest diffusion-based activation energy of 1.358 KJmol −1, and the highest diffusion current. This work successfully show that pH gradient contributes to an additional diffusive current in supercapacitor electrodes and the diffusion current improves the overall specific capacitance. The work also show that pH gradient creates an overpotential that consequently improves the energy density of the electrodes. The retention capacities of 94%, 92% and 91% were obtained for the 6–8, 4–10 and 2–12 respective pH gradients, to establish that pH gradient had no obvious effect on the retention capacity of the electrodes.

Keywords

• pH gradient
• Cellulosic electrodes
• Supercapacitor
• Energy density