Biowaste derived activated carbon electrocatalyst for oxygen reduction reaction: Effect of chemical activation

Abstract

Conversion of bio-wastes to useful doped carbon materials for various energy applications is emerging as a cost-effective strategy. A novel activated carbon electrocatalyst derived from chicken feather rachis (RCF), a poultry industry bio-waste is explored for oxygen reduction reaction (ORR) catalysis. The rachis is the central stem from which the fibrous ramus is completely removed and it is more crystalline compared to feather ramus. Nitrogen doped activated carbon (CNAx) electrocatalyst is prepared by chemical activation coupled pyrolysis. The chemical activators used include potassium hydroxide (KOH), phosphoric acid (H3PO4) and zinc chloride (ZnCl2) followed by pyrolysis at 500, 700 and 900 °C. Electrochemical performance has been evaluated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) using a rotating disk electrode (RDE). KOH activated electrocatalyst exhibits remarkable improvement in surface area favouring improved onset potential (−0.02 V vs Ag/AgCl). This increased activity is due to increase in number of well-exposed ORR active sites on activation. The effect of chemical activators on the structure and morphology of the activated carbons are discussed using Raman spectroscopy, adsorption-desorption isotherm study, electron microscopic techniques, atomic force microscopy (AFM), and XPS studies. KOH activated CNAx-900 exhibits best combination of properties and confirms its feasibility to be a suitable electrocatalyst for PEMFC. Hence, RCF derived electrocatalysts are propitious alternates for ORR catalysis.