MOF-on-MOF Strategy to Construct a Nitrogen-Doped Carbon-Incorporated CoP@Fe-CoP Core-Shelled Heterostructure for High-Performance Overall Water Splitting.

The design and preparation of efficient and low-cost catalysts for water electrolysis are crucial and highly desirable to produce eco-friendly and sustainable hydrogen fuel. Herein, we prepared nitrogen-doped carbon-incorporated CoP@Fe-CoP core-shelled nanorod arrays grown on Ni foam (CoP@Fe-CoP/NC/NF) through phosphorization of ZIF-67@Co-Fe Prussian blue analogue (ZIF-67@CoFe-PBA). The hierarchical nanorod arrays combined with the core-shelled structure offer favorable mass/electron transport capacity and maximize the active sites, thus enhancing the electrochemically active surface area. The synergistic effect of the bimetallic components and the nitrogen-doped carbon matrix endow the composite with an optimized electronic structure. Benefiting from the above superiorities of morphological and chemical compositions, this self-supported CoP@Fe-CoP/NC/NF heterostructure can drive alkaline hydrogen evolution reaction and oxygen evolution reaction with overpotentials of 97 and 270 mV to yield 100 mA cm ^-2 , respectively. The two-electrode alkaline electrolyzer constructed by this heterostructure shows a low cell voltage of 1.58 V to yield 10 mA cm ^-2 , superior to the precious-metal-based electrocatalyst apparatus (IrO ₂ ∥Pt/C). This study offers a feasible and facile approach to develop efficient electrocatalysts for water electrolysis, which applies to other electrochemical energy conversion and storage applications.