Electrostatically connected Fe2O3@Ni-MOF nanosheet array heterojunction for high-performance light-assisted zinc-air batteries

Using sunlight to accelerate the sluggish redox reaction at the cathode of zinc-air batteries is an effective strategy. Fe₂O₃ nanoclusters have excellent photovoltaic properties. However, the photocatalytic redox activity of single Fe₂O₃ is generally low because of severe charge recombination and insufficient redox catalytic sites. Herein, a Fe₂O₃@Ni-MOF nanosheet array (NA) composite exposing abundant Fe₂O₃ nanoclusters was designed and prepared for accelerating photocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). It was demonstrated that the Fe₂O₃@Ni-MOFNA heterojunction composites possessed a staggered S-type heterojunction that promoted charge separation and transfer under illumination. Theoretical calculations showed that Fe₂O₃@Ni-MOFNA composites had lower reaction free energies compared with the pristine component. Furthermore, the zinc-air battery yielded an output voltage of 1.76 V over the theoretical value and a round-trip efficiency of 98 % under illumination. This work provides a strategy for utilizing solar energy and developing light-assisted zinc-air batteries.