A Triatomic Cobalt Catalyst for Oxygen Electrocatalysis

The advancement of rechargeable zinc-air batteries significantly depends on bifunctional oxygen electrocatalysts to provide outstanding oxygen reduction/evolution reaction (ORR/OER) performance. However, it is still challenging to design electrocatalysts with excellent bifunctional activity and stability. Here, we adopt an ultrafast printing method to efficiently embed a triatom cobalt complex precursor onto graphene nanosheets to obtain a triatomic catalyst (Co₃-NG), exhibiting a durable and excellent bifunctional catalyst in the electrocatalytic ORR (E_half-wave = 0.903 V) and OER (E_{j = 10} = 1.596 V). The Co₃-NG-assembled zinc-air battery can output a maximum power density of 189.0 mW cm^-2 at 330 mA cm^-2 and can be charged and discharged over 3000 cycles, significantly outperforming the Pt/C + RuO₂ benchmark (146.5 mW cm^-2, 360 cycles) under testing conditions of 25 °C. In situ XAS analysis and theoretical calculations disclose that Co₃ON₆ is the catalytic site for bifunctional ORR/OER electrocatalysis. The constructed triangular pyramidal active sites effectively regulate the d-band center and electronic configuration and promote the adsorption/desorption of oxygen intermediates. This work uncovers that the geometry and electronic structure of triatomic active centers play a key role in improving bifunctional ORR/OER performance for electrochemical energy applications.