Bimetallic CoNi Alloy Nanoparticles Embedded in Pomegranate-like Nitrogen-Doped Carbon Spheres for Electrocatalytic Oxygen Reduction and Evolution

Electrocatalysts for oxygen reactions play a vital role in the applications of energy conversion devices, such as in fuel cells, water splitting, and metal–air batteries. Developing novel nonprecious bifunctional electrocatalysts is particularly essential for improved-performance metal–air batteries by overcoming sluggish oxygen reactions. Herein, we demonstrate a composite electrocatalyst with bimetallic CoNi alloy nanocrystals embedded within nitrogen-doped highly graphitic carbon spheres (N-CoNi/PCS). Owing to the efficient design strategy, such a composite electrocatalyst exhibits a unique pomegranate-like morphology and microstructure. When applied to an alkaline electrolyte system, the porous electrocatalyst delivers a low half-wave potential of 0.80 V toward ORR and overpotential of 540 mV toward OER with excellent durability. The high performance is systematically studied and ascribed to the unique nanoarchitecture which enables fast ion transportation and electron transfer, easy access to abundant active sites, and robustness. This work forwards the field of fabricating a highly active, affordable, and stable bifunctional electrocatalyst for energy conversion.