The fabrication of the FeSN/C electrocatalyst is schematically depicted in Scheme 1. The preparation of FeSN/C involves the utilization of Hb extracted from bovine blood, alkaline lignin (AL), tannic acid (TA) and urea as precursors. We hypothesized that that synergistic interaction between AL and TA with the haem centres in Hb would assist in forming N and S-enriched carbon structures supporting Fe single atom sites. Urea was added as an additional nitrogen source and as a porosity promoter. We varied the amounts of the different biomass components and urea to explore the effect of electrocatalyst composition and structure on ORR performance. Table lists the amount of each precursor used for synthesis of each catalyst. ). The C 1s spectrum for FeSN/C (Figure ) showed peaks at 284.4, 285.5, 287.8 and 290.6 eV which could readily be assigned to C-C/C=C, C-N/C-S, -CO2H and -* shake-up satellites, respectively. The N 1s spectrum of FeSN/C (Figure ) was deconvoluted into six peaks at 397.9, 398.9, 399.8, 400.9, 402.3 and 403.8 eV, which could readily be assigned to pyridinic N, Fe-Nx, pyrrolic N, graphitic N and two distinct N-oxide species, respectively. Pyridinic N and graphitic N were dominant N species in the sample, both of which are known to be beneficial for boosting ORR activity. The S 2p spectrum for FeSN/C (Figure ) showed peaks at 163. of a Fe 2+ or Fe 3+ species. A further set of peaks at higher binding energy, 717.4 eV (Fe 2p1/2) and 730.5 eV (Fe 2p1/2), are iron shake-up satellites. The XPS data thus shows that the FeSN/C catalyst contained a N,S-codoped carbon support rich in Heme-like (Fe-Nx) sites. Accordingly, the catalyst was expected to offer excellent performance for the ORR in alkaline media.