Biochar made from Luffa cylindrica and applied as a bifunctional electrocatalyst in Zn–air batteries

Abstract

Biochar has been prepared by pyrolysis of Luffa cylindrica (the vegetable sponge produced by Luffa aegiptiaca) and activated by mixing the pyrolyzed powder with KOH and pyrolyzed again. Non-activated and activated biochar have both been structurally and then electrochemically characterized to record their differences and assess their suitability as bifunctional oxygen reduction and oxygen evolution reaction electrocatalysts in Zn–air batteries. Non activated biochar carries several functional groups; however, the activation procedure led to a material with mainly O and Mg groups. Biochar activation improved its electrocatalytic properties, but both activated and non-activated luffa biochar were functional as bifunctional electrocatalysts to a satisfactory degree. This is justified by the fact that both carried a large percentage of carbon and graphitic carbon. The advantage of the non-activated biochar versus the activated biochar was its variety of functional groups while that of the activated biochar was its large specific surface area.