Unveiling Structure-Activity Relationship of Polyoxometallate-Confined Single Atom Electrocatalyst and...

The practical application of neutral Zn-air batteries (ZABs) is severely hindered by sluggish kinetics of oxygen reduction/evolution reaction (ORR/OER) and dendrite growth on the Zn anode. A precisely controlled preparation of Fe single atoms (FSAs) is achieved on a Fe-substituted H₃PW₁₂O₄₀∙nH₂O (abbr. {FePW₁₁O₃₉}) dotted Co/N doped carbon (Co-N-C), which ensures a well-dispersed, stable, and high loading (3.55%) of FSAs because the pore size (≈1 nm) of Co-N-C) is similar to the diameter of {FePW₁₁O₃₉}. FSAs show high ORR half-wave potential (0.824 V) and low OER potential (1.52 V) at 10 mA cm^-2 in neutral electrolyte. Density functional theory (DFT) calculations indicate that 4-fold hollow sites on {FePW₁₁O₃₉} are the most energetically favorable sites for ORR/OER, and the rate-determining step is *OH↔*O. Dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride groups are modified on polyvinylidene fluoride and then electrostatically connected with H₃PW₁₂O₄₀∙nH₂O anions to form a separator. The long chain groups and H₃PW₁₂O₄₀∙nH₂O promote OH^- transfer and minimize dendrite growth, confirmed by DFT. Solid ZABs with the FSA cathode and separator exhibit excellent performance within 60 to -60 °C, indicating that this strategy is highly promising for preparing advanced energy materials.