Adsorbed Cr(VI) based activated carbon/polyaniline nanocomposite: A superior electrode material for asymmetric supercapacitor device

Combating heavy metal pollution and energy crisis together, while maintaining the green chemistry standard is a great challenge. Among heavy metals, the toxicity of hexavalent chromium compounds is well known, one which can be adsorbed from water and can be used as an electrode for energy storage. In this work, a nanocomposite of exhausted activated carbon (extracted from commercial water filter) and polyaniline was used as an adsorbent for toxic Cr(VI) adsorption from mine water, and a high-performance asymmetric energy storage device was developed from it. Firstly, the adsorbent was explored for the proficient removal of toxic Cr(VI) from water. The adsorption data was found to be well fitted with the Langmuir isotherm, and the pseudo-second order kinetics suggested the monolayer chemisorbed nature. In the next step, the adsorbed material was investigated as the cathode material for supercapacitors. The nanocomposite based on Cr(VI)-adsorbed material exhibited a high specific capacitance of 219.6 F/g at 1 A/g current density and moderate cycling stability of 77% after 5000 charges/discharge cycles. An asymmetric device developed using this hybrid material achieved an elevated energy density of 60.8 Wh/kg in organic electrolyte. The device was used to light up a strip of 43 red LEDs connected in parallel.