High Energy Efficiency on Zn–Air/Iodide Hybrid Batteries with Iron Phthalocyanine Coupled Co Single Atoms Dual Active Sites

Rechargeable zinc–air batteries (ZABs) are hindered by substantial voltage hysteresis and limited cycling stability. To address these challenges, a dual-innovation strategy is developed through synergistic electrolyte engineering and catalyst design. First, electrolyte engineering is implemented through the incorporation of KI into the electrolyte, transforming conventional ZABs into zinc–air/iodide hybrid batteries (ZAIHBs). This modification replaces the oxygen evolution reaction (OER) with the iodine oxidation reaction (IOR), which operates at a significantly reduced overpotential. Second, FePc@CoSAs/NC catalyst is constructed by anchoring iron phthalocyanine (FePc) on Co single-atom/N-doped carbon substrates. FePc@CoSAs/NC exhibiting a half-wave potential of 0.89 V for ORR and achieving 1.26 V at 10 mA cm⁻² for IOR with a record-low ORR/IOR voltage gap of 0.37 V. The optimized ZAIHBs demonstrate exceptional energy efficiency of 75% and cycling stability (73.5% retention over 350 h), surpassing conventional ZABs. Density functional theory calculations reveal that the Co–Fe dual-site coordination optimizes adsorption energetics for critical reaction intermediates (OH* in ORR and I* in IOR), elucidating the enhanced reaction kinetics. This work establishes a co-design paradigm for high-performance hybrid energy systems through integrated electrolyte and catalyst engineering.