Schiff-base polymer derived ultralong FeCo/N-doped carbon nanotubes as bifunctional oxygen electrocatalyst for liquid and flexible all-solid-state rechargeable zinc–air batteries

Controllable designing of robust and cost-effective bifunctional electrocatalysts toward oxygen reduction/evolution reaction (ORR/OER) is essential to zinc-air batteries (ZABs) but still a challenge. Herein, a promising strategy is proposed to construct a bifunctional oxygen electrocatalyst composed of FeCo alloy nanoparticles embedded in ultralong N-doped carbon nanotubes (FeCo-LCNT). The in-situ catalytic generated FeCo-LCNT is yielded via the condensation polymerization of 2,5-dihydroxy-p-benzoquinone and tripolycyanamide, followed by the coordination with Fe3+/Co2+ ions and subsequent pyrolysis. The as-obtained FeCo-LCNT manifests improved bifunctional activity and durability in comparison with commercial Pt/C and IrO2. The experimental results and DFT calculations demonstrate that the interaction between alloy nanoparticles and CNT and the presence of N-doped carbon species are of crucial importance in enhancing the catalytic activities of the FeCo-LCNT. Impressively, the FeCo-LCNT can serve as air-electrode catalyst, endowing the assembled rechargeable liquid and flexible all-solid-state ZABs with good high-rate performance, long cyclic life (for the former) and enhanced stability at various bending angles (for the latter).