PBA-derived FeCo alloy with core-shell structure embedded in 2D N-doped ultrathin carbon sheets as a bifunctional catalyst for rechargeable Zn-air batteries

To overcome slow kinetics of oxygen reduction/evolution reactions (ORR/OER), the development of bifunctional electrocatalysts remains a huge challenge. FeCo alloy as an active-species usually suffers from its poor catalytic stability by easy corrosion. Here, we synthesize a core (FeCo)-shell (carbon) alloy anchored on nitrogen-doped porous carbon-nanosheets (FeCo/NUCSs) via a self-growth strategy. FeCo/NUCSs (140 m2 g-1) exhibits promising half-wave potential (E1/2 =0.89 V) and methanol tolerance for ORR. Prussian blue analog-derived carbon shell protects binary active-sites (Fe-Nx/Co-Nx) on FeCo core to stabilize ORR activity. FeCo/NUCSs also displays a higher OER activity (overpotential of 300 mV) than RuO2, due to generation of highly-active FeOOH/CoOOH species on FeCo alloys as indicated by in situ X-ray diffraction. Assembled Zn-air battery (ZAB) exhibits promising open-circuit voltage of 1.51 V, specific capacity of 791.86 mA h g-1, and durability (102 h). This novel bimetallic alloy-based catalyst provides an interesting option for design of durable oxygen-electrocatalysts for ZAB.