Fe-N-C Self-Doped Sewage Sludge-Derived Biocarbon With Catalytic Activity For The Oxygen Reduction Reaction

The development of numerous biomass-derived carbon catalysis toward the oxygen reduction reaction (ORR) have been reported in the last decade. The catalytic activity for the ORR improves with heteroatom doping and is notably high when Fe-N-C type bonds are present. In this work, we developed a novel method to obtain Fe-N-C self-doped sewage sludge-derived biocarbons (SSBs) by intermittent microwave heating (IMH) technique. The effect of IMH on the structural and textural properties of SSBs, and their correlation with the catalytic activity for ORR was studied. The most active biocarbon was labeled as SSF, which was obtained by two-step process: chemical activation using KOH and then it was functionalized with methanol by IMH. Therefore, the obtained SSF micro-mesoporous biocarbon had high surface area (1127 m2 g-1) and quaternary-N and thiophene-S species. In addition, Fe-N-C bonds were detected on the surface of SSF. On the other hand, it was observed that IMH treatment improved the electrochemical parameters such as the on-set potential (E0), current density (j), electron transfer number (n) and %HO2 - production. In this regard, SSF shows the best performance toward the ORR (E0= 0.89 V vs RHE, j= -3.01 mA cm-2, n= 3.4 and %HO2 - = 25.85). These results indicate that sewage sludge could be used as raw material for the manufacture of cathodes, and that the treatment by IMH seems a promising eco-friendly alternative.