Fully conjugated covalent organic polymers with FeN4 sites and adjacent Co nanoparticles synergistic catalysis for ultra-stable zinc-air batteries

Elaborate designed active sites and reasonable regulation of their electronic structure to develop efficient electrocatalysts are essential yet challenging for promoting the practical applications of zinc-air batteries. Instead of randomly fabricating metal‑nitrogen moieties on a carbon matrix by pyrolysis, an efficient composite electrocatalyst (Fe-COP/Co@HCF) is constructed in this study through π-π interaction between the well-designed π conjugated iron-covalent organic polymers (Fe-COP) with the atomically Fe N 4 centers and hollow carbon nanofibers supported by Co nanoparticles (Co@HCF) with high electrical conductivity and mass transfer capability. Additionally, the optimized Fe-COP/Co@HCF exhibits an outstanding electrocatalytic activity with a half-wave potential of 0.90 V (vs. RHE), attributed to the synergistic effect and intrinsic activity of the Fe N 4 moiety, as well as the unique hollow porous structure of carbon nanofibers. Density functional theory calculations demonstrate a significant electron rearrangement occurs around Fe centers, accompanied by the d-band center upshift, which effectively reduces the energy barrier for oxygen intermediate adsorption and accelerates the ORR kinetics. Notably, the liquid zinc-air battery assembled with Fe-COP/Co@HCF catalyst as a cathode achieves a peak power density of 204 mW cm −2 with extremely long-term stability (>2300 h). This work provides a feasible method for precisely designing active sites of electrocatalysts.