B-site W ion-doped La0.5Sr0.5Co1−xWxO3−δ perovskite nanofibers with defects as bifunctional oxygen catalysts for rechargeable zinc-air batteries

The exploration of bifunctional oxygen electrodes towards oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is the bottleneck for the development of rechargeable zinc-air batteries as clean energy storage and conversion devices. In this work, a series of porous La0.5Sr0.5Co1−xWxO3−δ perovskite nanofibers with a high ratio of Co2+/Co3+ and oxygen defects were prepared by doping W ions at B-sites. It was revealed that the W dopant effectively optimized the electronic structures of La0.5Sr0.5Co1−xWxO3−δ (x = 0.3), which not only reduced the electron numbers of the eg orbital, but also regulated the O 2p-band closer to the Femi level, calculating for the expressively enhanced bifunctional oxygen catalytic activity. Optimized LSCW0.3 possessed a low oxygen evolution potential of 1.58 V vs. RHE to reach a current density of 10 mA cm−2 and an excellent long-term stability for 50 hours in 1 M KOH electrolyte. In addition, LSCW0.3 with the efficient bifunctional oxygen catalytic activity was used as the cathode in the rechargeable zinc-air battery. The LSCW0.3-based zinc-air battery delivered a high power density of 121.23 mW cm−2 at a current density of 156 mA cm−2, which was much higher than that of the Pt/C + RuO2-based zinc-air battery. The LSCW0.3-based zinc-air battery demonstrated a stable voltage gap after 1000 galvanostatic charge–discharge cycle tests.