Tannic acid-derived metal–phenolic networks with dual-atom ORR and single-atom OER sites for bifunctional oxygen electrocatalysts

Abstract

Developing highly efficient and cost-effective bifunctional oxygen electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critical for the widespread application of rechargeable zinc–air batteries. Herein, we report a green-synthesized, tannic acid-derived metal–phenolic networks electrocatalyst featuring well-defined dual-atom ORR sites and single-atom OER sites, which synergistically deliver exceptional bifunctional activity. The unique structure originates from the precise coordination of earth-abundant metal ions with the polyphenol ligand of natural tannic acid, providing well-defined active sites and efficient mass/electron transport. The optimized catalyst Co_0.85Fe_0.15@TA-Salphen exhibits outstanding ORR performance with a half-wave potential of 0.923 V (vs. RHE) and superior OER activity with an overpotential of only 282 mV at 10 mA cm⁻², surpassing most reported bifunctional catalysts. When integrated into zinc–air batteries, the catalyst demonstrates high power density (198 mW cm⁻²) and excellent cycling stability (over 500 cycles), highlighting its potential for practical applications. This work not only presents a high-performing and durable bifunctional oxygen electrocatalyst with well-defined ORR/OER active sites but also highlights the potential of green, biomass-derived materials for advanced energy applications.