Interfacial engineering of heterostructured CoP/FeP nanoflakes as bifunctional electrocatalyts toward alkaline water splitting.

Exploring highly-effective and nonprecious electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is urgent and challenging for developing the hydrogen economy. Interface engineering is a feasible approach for regulating the surface electronic distribution, thereby promoting the catalytic performance. Herein, the CoP/FeP heterostructure is fabricated via the oxidation and phosphating treatments of Fe-decorated Ni(OH)2 nanoflakes. The hierarchically porous nanoflakes can expose more active species, while the formation of CoP/FeP heterojunctions have provided extra catalytic active sites and accelerated the charge transfer process. Theoretical calculations reveal that the interfacial electron coupling between CoP and FeP in the heterostructure has promoted the adsorption of intermediate species on catalytic sites, thereby decreasing the Gibbs free energy during the catalysis. The as-fabricated CoP/FeP catalyst requires small overpotentials of 190 mV and 280 mV to realize a current density of 10 mA cm-2 for alkaline HER and OER, respectively. The electrolytic cell with CoP/FeP as catalyst needs a voltage of 1.61 V to reach 10 mA cm-2, and can run stably for over 25 h. The present study highlights a superiority of interfacial engineering to construct efficient electrocatalysts for water electrolysis.