High-Voltage aqueous supercapacitors based on l-lysine pH Self-Buffering Coating-modified carbon cloth electrode

Achieving a high working voltage window beyond the water electrolysis limit (1.23 V) is always a challenge for aqueous supercapacitors (SCs). Increasing the oxygen evolution reaction (OER) overpotential or hydrogen evolution reaction (HER) overpotential of the carbon-based electrode is an effective way to broaden the voltage window of SCs. In this work, we propose an efficient strategy of surface engineering to autonomously regulate the pH of the electrode/electrolyte interface microenvironment by using the amphoteric dissociation of amino acids, which suppress the OER and consequently broadens voltage window. L-Lysine was modified on the surface of carbon cloth to prepare the SC positive electrode. The voltage window of SCs based on L-Lysine modified electrode is enhanced from 1.2 V to 1.5 V and the energy density has increased by 59.42 % at 0.5 A g −1 . This is a promising strategy to design and engineer carbon-based aqueous SCs with a boosted energy density.