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

Abstract

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 Fe_xCo_1−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.