Paired Fe Single-Atoms Coordinated by N and Se as Oxygen Electrocatalysts for High-Performance Zinc-Air Battery

In recent years, zinc-air battery (ZAB) has received great attention because of their high energy density, low manufacturing cost, environmental friendliness, and high safety. The main obstacle to the widespread use of ZAB is the design and preparation of low-priced and high-performance electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, the paired Fe single-atoms with Se, N-atom coordination supported on N, S-codoped carbon (FeN_xSe_y@SNC) are designed and synthesized as catalyst for ZABs. The physical and chemical characterizations indicate the existence of paired Fe single-atoms. The FeN_xSe_y@SNC exhibits exceptional ORR catalytic activity with a half-wave potential (E_1/2) of up to 0.92 V_RHE and an onset potential (E_onset) of 1.057 V_RHE and a overpotential of 346 mV for OER at 10 mA cm^-2. The FeN_xSe_y@SNC-based ZAB shows a high peak power density of 307 mW cm^-2 at 475 mA cm^-2, a high specific energy density of 760.9 mAh g^-1 at 10 mA cm^-2, and superior long-term durability. DFT reveal that the asymmetric Fe─Se─Fe bridging bonds and S-atom coordination in the Fe₂N₅SeS allow precise control of Fe active sites, and can well modulate the electronic properties of Fe sites, optimize the adsorption energies of oxygen intermediates and improve catalytic performance.