FePc-Modified CoFe₂O₄ Synergistic Boost Oxygen Electrocatalysis for Metal-Air Batteries

A key challenge in metal-air batteries (MAB) is the slow kinetics of both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Therefore, it is necessary to develop catalysts that can optimize their kinetic performance. Herein, a bifunctional catalytic material, FePc-CoFe₂O₄/CNT, was fabricated through a scalable and facile method due to the π-π stacking effect. The introduction of FePc promotes electron transfer from the Fe sites in FePc and the Co sites in CoFe₂O₄ to the lattice oxygen in CoFe₂O₄. This process not only overcomes the poor intrinsic conductivity of FePc and enhances the catalytic activity of the Fe-N₄ sites but also increases the number of Co³⁺ active sites. Systematic investigations demonstrate that the synergistic interaction between FePc and CoFe₂O₄/CNT markedly accelerates the reaction kinetics, resulting in a reduced potential gap between the OER potential at 10 mA cm^-2 and the ORR half-wave potential (ΔE = 0.82 V). When used as an air electrode in aqueous zinc-air batteries (ZAB), the catalyst achieves a power density of 199.5 mW cm^-2 and stable cycling for over 1000 h at a current density of 2 mA cm^-2, outperforming the benchmark Pt/C + RuO₂. Remarkably, the catalyst also exhibits excellent performance in lithium-air batteries (LAB), maintaining a capacity retention rate of 99.8% after 225 cycles. This study provides valuable insights into the design of catalysts for MAB.