Enhanced oxygen reduction reaction for Zn-air battery at defective carbon fibers derived from seaweed polysaccharide

Carbon fibers with intrinsic carbon defects (D-CFs) were fabricated through heteroatoms doping and de-doping using seaweed polysaccharide as the precursor. When evaluated as oxygen reduction reaction (ORR) electrocatalyst, D-CFs display an initial potential of 0.92 V (vs. RHE) and a limiting diffusion current density of 5.38 mA·cm−2 in KOH electrolyte (0.1 M). The high peak power density of zinc-air batteries (ZABs) assembled by D-CFs is 238 mW·cm−2, that is much better than commercial Pt/C (154 mW·cm−2). In the light of density functional theory (DFT) results, enriched electrons in defects make the hybridization energy levels of active defective sites and adsorbed oxygen atoms rise to Fermi level, indicating that O2 molecules are inclined to be adsorbed onto defective carbon atoms. Therefore, abundant renewable seaweed sources, together with the excellent ORR catalytic activity, make D-CFs as the substitute of Pt/C catalyst for large-scale application of ZABs.