A Green Approach to High-Performance Supercapacitor Electrodes: The Chemical Activation of Hydrochar with Potassium Bicarbonate

Sustainable synthesis schemes for the production of porous carbons with appropriate textural properties for use as super-capacitor electrodes are in high demand. In this work a greener option to the widely used but corrosive KOH is proposed for the production of highly porous carbons. Hydrochar products are used as carbon precursors. It is demonstrated that a mild alkaline potassium salt such as potassium bicarbonate is very effective to generate porosity in hydrochar to lead to materials with large surface areas (>2000 m(2)g(-1)) and a tunable pore size distribution. Furthermore, the use of KHCO3 instead of KOH gives rise to a significant 10% increase in the yield of activated carbon, and the spherical morphology of hydrochar is retained, which translates into better packing properties and reduced ion diffusion distances. These features lead to a super-capacitor performance that can compete with, and even surpass, that of KOH-activated hydrochar in a variety of electrolytes.