Highly Active CoNi-CoN 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 composite site containing CoNi alloyed nanoparticles and CoN moieties is first constructed in N-doped carbon nanosheet matrix (CoNi-CoN/C). Benefiting from the high electroactivity of CoNi-CoN composite sites and large surface area, CoNi-CoN/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. Theoretical calculations have demonstrated that the introduction of CoNi alloys has modulated the electronic distributions near the CoN moiety, inducing the d-band center of CoNi-CoN 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/C as catalyst, a large power density (250 mW cm) and high specific capacity (804 mAh g) are achieved. The in-depth understanding of the electroactivity enhancement mechanism of interactive metal nanoparticles and metal coordinated with nitrogen (MN) moieties is crucial for designing novel high-performance metal/nitrogen-doped carbon (M─N─C) catalysts.