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CoP2/Fe-CoP2 yolk-shell nanoboxes as efficient electrocatalysts for the oxygen evolution reaction.

The development of an efficient electrocatalyst is an important requirement for water splitting systems to produce clean and sustainable hydrogen fuel. Herein, we synthesized CoP2/Fe-CoP2 yolk-shell nanoboxes (YSBs) as efficient electrocatalysts for the oxygen evolution reaction (OER). Initially, zeolitic imidazolate framework-67/CoFe-Prussian blue analogue (ZIF-67/CoFe-PBA) YSBs were prepared by the reaction of ZIF-67 and [Fe(CN)6]3- ions in the presence of a small amount of water as an etching agent. The size of the CoP2 yolk depends on the amount of water. The heteronanostructure composed of the CoP2 yolk and the FexCo1-xP2 shell with a cubic shape was obtained by phosphidation of ZIF-67/CoFe-PBA YSBs. Benefiting from the unique structure and chemical composition, the CoP2/Fe-CoP2 YSB electrocatalyst has a large specific surface area of 114 m2 g-1 and shows superior electrocatalytic performances for the OER such as a low overpotential of 266 mV, a small Tafel slope value of 68.1 mV dec-1, and excellent cyclic stability.