Self-Templated Synthesis of CoFeP @ C Cage-In-Cage Superlattices for Enhanced Electrocatalytic Water Splitting

Designing highly-efficient, cost-effective, and stable electrocatalysts for water splitting is of great significance for implementing renewable energy technologies. Herein, a self-templated strategy is employed to fabricate 2D porous electrocatalysts of heterometallic phosphides featuring a cage-in-cage superlattice architecture. The as-made heterometallic phosphide electrocatalysts, comprising a layer of close-packed CoFeP nanocages intimately embedded in an interconnected carbon-cage framework, are converted from carbon-coated CoFeO nanocrystal superlattices by one-step phosphidation. Benefiting from the unique hierarchical porous structure and the ability of modulating the Co/Fe molar ratio, such 2D CoFeP @ C cage-in-cage superlattices show remarkable activity and stability for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. Moreover, water electrolyzers constructed using CoFeP @ C superlattices as both cathode and anode require a low cell voltage of 1.55 V to achieve a current density of 10 mA cm(-2), outperforming most nonprecious metal-based electrocatalysts reported previously. The superior electrocatalytic performance of CoFeP @ C superlattices is revealed by density functional theory calculations. These findings provide new opportunities for developing efficient and stable bifunctional electrocatalysts for water splitting.