Highly Active CoNi-CoN₃ Composite Sites Synergistically Accelerate Oxygen Electrode Reactions in Rechargeable Zinc-Air Batteries

Reaching rapid reaction kinetics of oxygen reduction (ORR) and oxygen evolution reactions (OER) is critical for realizing efficient rechargeable zinc-air batteries (ZABs). Herein, a novel CoNi-CoN₃ composite site containing CoNi alloyed nanoparticles and CoN₃ moieties is first constructed in N-doped carbon nanosheet matrix (CoNi-CoN₃/C). Benefiting from the high electroactivity of CoNi-CoN₃ composite sites and large surface area, CoNi-CoN₃/C shows a superior half-wave potential (0.88 V versus RHE) for ORR and a small overpotential (360 mV) for OER at 10 mA cm^-2. Theoretical calculations have demonstrated that the introduction of CoNi alloys has modulated the electronic distributions near the CoN₃ moiety, inducing the d-band center of CoNi-CoN₃ composite site to shift down, thus stabilizing the valence state of Co active sites and balancing the adsorption of OER/ORR intermediates. Accordingly, the reaction energy trends exhibit optimized overpotentials for OER/ORR, leading to superior battery performances. For aqueous and flexible quasi-solid-state rechargeable ZABs with CoNi-CoN₃/C as catalyst, a large power density (250 mW cm^-2) and high specific capacity (804 mAh g^-1) are achieved. The in-depth understanding of the electroactivity enhancement mechanism of interactive metal nanoparticles and metal coordinated with nitrogen (MN_x) moieties is crucial for designing novel high-performance metal/nitrogen-doped carbon (M─N─C) catalysts.