Core–Ring Structured NiCo 2 O 4 Nanoplatelets: Synthesis, Characterization, and Electrocatalytic Applications

An innovative nanostructure, namely the core–ring structure, is reported in this paper. It occurs in NiCo 2 O 4 nanoplatelets, synthesized by the coprecipitation decomposition method using sodium hydroxide as the precipitant. The yield of core–ring hexagonal NiCo 2 O 4 nanoplatelets is greater than 80% at 200 °C. A high‐resolution transmission electron microscopy and energy dispersive spectroscopy investigation reveals the typical core–ring nanostructure, which shows a strong enrichment of Co in the core with a Co content higher than 80%. A mechanism for the core–ring structure formation is proposed. The core–ring NiCo 2 O 4 can be used as an electrocatalyst for an oxygen evolution reaction (OER) in alkaline water electrolysis. Compared with the electrodes of ordinary NiCo 2 O 4 and Co 3 O 4 , or other NiCo 2 O 4 electrodes prepared by alternate methods, the electrode coated by core‐ring NiCo 2 O 4 nanoplatelets exhibits the greatest electrocatalytic properties, with an over‐potential of 0.315 V at a current density of 100 mA cm −2 .