Efficient unitary oxygen electrode for air-based flow batteries

Air-based flow batteries have triggered huge interests as promising large-scale energy storage devices due to their high energy density and extremely low cost. However, the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) lower their energy conversion efficiencies. Herein, we in situ grow amorphous NiSx-FeOy particles on sulfur doped carbon fiber paper (termed as NiSx-FeOy/SCFP) as practical self-supported oxygen electrode through a simple and economic synthesis route. Benefiting from the synergetic effects of amorphous NiSx-FeOy and SCFP, NiSx-FeOy/SCFP possesses massively accessible active sites, enhanced electrons and reactants transfer, and stable integrated structure, exhibiting a low overpotential (0.37 V) at 10 mA cm(-2) for OER, a positive half-wave potential for ORR and a small potential gap (0.82 V). Zinc air flow battery assembled with newly developed NiSx-FeOy/SCFP shows a coulombic efficiency of 100% and a voltage efficiency of 50% at the charge-discharge current of 10 mA cm(-2), and vigorously operates 110 h without performance decay, showing highly catalytic activity and super cycling stability, which are among the best performance ever reported. We believe that this work will open up new ways for fabricating practical oxygen electrode for metal air based batteries applications.