Co@Co3O4@PPD Core@bishell Nanoparticle‐Based Composite as an Efficient Electrocatalyst for Oxygen Reduction Reaction

Durable electrocatalysts with high catalytic activity toward oxygen reduction reaction (ORR) are crucial to high‐performance primary zinc‐air batteries (ZnABs) and direct methanol fuel cells (DMFCs). An efficient composite electrocatalyst, Co@Co 3 O 4 core@shell nanoparticles (NPs) embedded in pyrolyzed polydopamine (PPD) is reported, i.e., in Co@Co 3 O 4 @PPD core@bishell structure, obtained via a three‐step sequential process involving hydrothermal synthesis, high temperature calcination under nitrogen atmosphere, and gentle heating in air. With Co@Co 3 O 4 NPs encapsulated by ultrathin highly graphitized N‐doped carbon, the catalyst exhibits excellent stability in aqueous alkaline solution over extended period and good tolerance to methanol crossover effect. The integration of N‐doped graphitic carbon outer shell and ultrathin nanocrystalline Co 3 O 4 inner shell enable high ORR activity of the core@bishell NPs, as evidenced by ZnABs using catalyst of Co@Co 3 O 4 @PPD in air‐cathode which delivers a stable voltage profile over 40 h at a discharge current density of as high as 20 mA cm −2 .