Biomass Electrocatalysts: Exploiting Haemoglobin-derived Fe Sites Supported by Waste-derived, S and N-enriched Carbon for Efficient Oxygen Electro-reduction

Abstract

Biomass resources offer a diverse array of low-cost feedstocks having interesting functional properties for the manufacture of electrocatalysts for the energy sector. In this study, haemoglobin (Hb), lignin, tannic acid and urea were used to make high surface area S, N-codoped carbon electrodes rich in highly dispersed heme-like (Fe-Njats:subx</jats:sub>) sites. By pyrolyzing precursor mixtures containing un-purified Hb, lignin, tannic acid and urea, in appropriate mass ratios, a high surface-area S, N-codoped carbon nanostructured electrocatalyst was obtained. The electrocatalyst had surface pyridinic and pyrrolic species together with highly dispersed N-coordinated Fe sites. 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 of 0.87 V and a low Tafel slope of 54 mV/dec. This work encourages the design of biomass-derived electrocatalysts for ORR, in particular showing that haemoglobin in bovine blood is suitable for use as an iron source when making Fe-N-C electrocatalysts.