Multi‐chambered, carbon‐coated Ni 0.4 Fe 2.6 O 4 nanoparticle superlattice microspheres for boosting water oxidation reaction

Developing active and robust non‐noble‐metal‐based electrocatalysts for the oxygen evolution reaction (OER) is of vital practical significance for accelerating the kinetics of water splitting. Here, a novel double emulsion template method is proposed to design and prepare hierarchically multichambered, carbon‐coated Ni 0.4 Fe 2.6 O 4 nanoparticle superlattice microspheres (M‐NFO@C‐NSMs) for the highly efficient oxygen evolution. The high‐temperature calcination under inert gas enables an improved electrochemical property by rationally transforming the long‐chain organic capping ligands into partially graphitized uniform carbon coatings. More importantly, benefiting from the unique hierarchical superstructure with macro‐/meso‐/microporosities and three‐dimensional continuous conductive carbon frameworks, M‐NFO@C‐NSMs exhibit comprehensively enhanced OER activity in a dilute alkaline electrolyte as compared to their solid counterparts and most spinel‐based electrocatalysts reported to date. Notably, the collective property of supraparticles endowed M‐NFO@C‐NSMs with superior long‐term cyclic stability. This work sheds light on the sophisticated design of functionalized supraparticles for efficient water splitting.