Rigid ligand confined rapid synthesis of dual single-atomic sites on carbon black for enhanced oxygen depolarized cathodes

Oxygen reduction reaction (ORR) is crucial for Zn-air batteries, while also serves as a core electrochemical process in oxygen depolarized cathodes (ODCs) for chlor-alkali electrolysis. The lack of cost-effective, highly active ORR electrocatalysts with superior kinetics hinders progress in this field. Herein, we report the Fe/Ni dual single-atomic sites anchored by commercial carbon black (Fe/Ni-N/CB) using rigid ligand confined and high-temperature shock (HTS) strategy in less than 0.5 s. Theoretical calculation reveals that single-atomic Fe is the real active site. Single-atomic Fe and Ni species in Fe/Ni-N/CB synergistically accelerate the kinetics of ORR by reducing the energy barrier of the rate-determining step. A large half-wave potential (E_1/2) of 0.907 V is achieved in 0.1 M KOH aqueous solution. The assembled aqueous Zn-air battery (A-ZAB) with Fe/Ni-N/CB cathode presents remarkable charge-discharge cycling stability for over 650 h without voltage gap degradation. The quasi-solid-state Zn-air battery (QSS-ZAB) exhibits excellent reversibility over a 150-h operation at 0.5 mA cm⁻² with negligible energy conversion efficiency recession. Impressively, Fe/Ni-N/CB||RuO₂ chlor-alkali flow cell exhibits a low cell voltage of 1.60 V at a large current density of 300 mA cm⁻² at 80 °C, and demonstrates exceptional durability with 7% current density decay over 150 h of continuous operation at 100 mA cm⁻². Fe/Ni-N/CB||RuO₂ achieves near-ideal caustic current efficiency (~97.2%) at the current density of 300 mA cm⁻². This work provides a rapid and economical synthesis technique for the synthesis of catalysts at the atomic scale while demonstrating significant potential for application in energy-saving chlor-alkali electrolyzer.