Engineering Electronic and Morphological Structure of Metal-Organic-Framework-Derived Iron-Doped NiP/NC Hollow Polyhedrons for Enhanced Oxygen Evolution.

The rational design of an oxygen electrocatalyst with low cost and high activity is greatly desired for realization of the practical water-splitting industry. Herein, we put forward a rational method to construct nonprecious-metal catalysts with high activity by designing the microstructure and modulating the electronic state. Iron (Fe)-doped NiP hollow polyhedrons decorated with nitrogen-doped carbon (Fe-NiP/NC HPs) are prepared by a sequential metal-organic-framework-templated strategy. Benefiting from the strong electronic coupling, rapid charge-transfer capability, and abundant catalytic active sites, the obtained Fe-NiP/NC HPs exhibit an impressive electrocatalytic performance toward the oxygen evolution reaction (OER) with an ultralow overpotential of 228 mV at a current density of 10 mA cm and a small Tafel slope of 33.4 mV dec, superior to the commercial RuO and most reported electrocatalysts. Notably, this catalyst also shows long durability with an almost negligible activity decay over 210 h for the OER. Combining density functional theory calculations with experiments demonstrates that the doped Fe and the incorporated carbon effectively modulate the electronic structure, enhance the conductivity, and greatly reduce the energy barrier of the rate-determining step in the process of OER. Thus, fast OER kinetics is realized. Moreover, this synthetic strategy can be extended to the synthesis of Fe-NiS/NC HPs and Fe-NiSe/NC HPs with excellent OER performance and long-term durability. This work furnishes an instructive idea in pursuit of nonprecious-metal materials with robust electrocatalytic activity and long durability.