Highly Active CoNi-CoN 3 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-CoN 3 composite site containing CoNi alloyed nanoparticles and CoN 3 moieties is first constructed in N-doped carbon nanosheet matrix (CoNi-CoN 3 /C). Benefiting from the high electroactivity of CoNi-CoN 3 composite sites and large surface area, CoNi-CoN 3 /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 CoN 3 moiety, inducing the d-band center of CoNi-CoN 3 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-CoN 3 /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.