Biomass-derived nanoporous carbons as electrocatalysts for oxygen reduction reaction

Abstract

Electrocatalysts (ECs) for the oxygen reduction reaction (ORR) are crucial in fuel cells and for this reason developing cost-effective metal-free ECs with high electrocatalytic activity and high-volume production remains a huge challenge. Herein, we report the application as ORR electrocatalysts of a series of high grade nanoporous carbons, prepared by chemical activation of acid-chars obtained from the H2SO4 digestion and polycondensation (acid-mediated carbonization) of a biomass residue (Agave sisalana).All the nanoporous carbons presented good ORR electrocatalytic activities in alkaline medium. The AC1 carbon exhibited the most promising ORR performance with Eonset = 0.84 vs. RHE, jL, 0.26 V, 1600 rpm = -3.12 mA cm−2 and nO2 = 3.6 electrons. The Tafel slopes of all carbons varied between 47 mV dec−1 (AC3) and 250 mV dec−1 (AC1). Furthermore, the carbons revealed superior tolerance to methanol when compared with commercial Pt/C and a competitive long-term electrochemical stability, with current retentions of 75–85 % after 20,000 s.The results obtained in this work suggest a promising method based on sustainable and economical biomass residues towards the development and engineering of novel value-added biomass-derived carbons as effective metal-free electrocatalysts for alkaline fuel cells.