Biomass Electrocatalysts: Exploiting Haemoglobin-derived Fe Sites Coordinated with S, N-enriched Carbon for Efficient Oxygen Electro-reduction

Biomass resources offer a diverse array of low-cost feedstocks for the manufacture electrocatalysts for the energy sector. In this study, haemoglobin (Hb), lignin, tannic acid and urea were used to develop FeSN/C electrocatalysts comprising iron highly dispersed on S,N-codoped carbon for the oxygen reduction reaction (ORR). By pyrolyzing precursor mixtures containing Hb, lignin, tannic acid and urea in appropriate mass ratios, S,N-codoped carbons with highly dispersed Fe sites were obtained with ORR performance superior to Pt/C. The developed FeSN/C electrocatalyst exhibited an ORR onset potential of 0.98 V vs. RHE in 0.1 M KOH, a half-wave potential (E1/2) of 0.87 V and a low Tafel slope of 54 mV/dec. Notably, the electrocatalyst selectively catalysed the 4-electron ORR pathway and exhibited a high methanol tolerance. This work encourages the design of biomass-derived electrocatalysts for oxygen reduction reaction, in particular showing that haemoglobin in bovine blood is a suitable for use an iron source when making Fe-N-C electrocatalysts.