Direct Growth of CoFe2 Alloy Strongly Coupling and Oxygen‐Vacancy‐Rich CoFe2O4 Porous Hollow Nanofibers: an Efficient Electrocatalyst for Oxygen Evolution Reaction

Abstract

AbstractEfficient electrocatalysts for the oxygen evolution reaction (OER) is crucial for improving the performance of metal−air batteries and water splitting. In this study, the CoFe2 alloy strongly coupling and oxygen‐vacancy‐rich CoFe2O4 (CoFe2 alloys/CoFe2O4) porous hollow complex nanofibers, as a highly efficient and stable electrocatalyst for OER, have been synthesized via a facile method of electrospinning combining with two‐step heat treatment. The obtained CoFe2 alloys/CoFe2O4 porous hollow complex nanofibers show high electrical conductivity with the smaller charge transfer resistance than that of the commercial RuO2, and even two orders of magnitude lower than that of the single CoFe2O4 porous hollow nanofibers. When used as an electrocatalyst for OER, it demonstrates a superior electrochemical performance with an over‐potential of 300 mV at the current density of 10 mA cm−2, which is comparable to that of the commercial RuO2 but obviously better than that of the single CoFe2O4 porous hollow nanofibers. Moreover, the CoFe2 alloys/CoFe2O4 porous hollow complex nanofibers exhibit remarkably stability with negligible potential increase of only 1.2 % at high current density of 100 mA cm−2 for 16 h. Meanwhile, the CoFe2 alloys/CoFe2O4 porous hollow complex nanofibers also show an excellent hydrogen evolution reaction (HER) activity, affording an over‐potential of 152 mV at the current density of 10 mA cm−2. When using for water splitting in 1 M KOH, the CoFe2 alloys/CoFe2O4 porous hollow complex nanofibers delivers a current density of 10 mA cm−2 at a cell voltage of 1.687 V. More important, the direct growth of CoFe2 alloys on the CoFe2O4 base of the porous hollow nanofibers can be an effective way to control the coupling of the CoFe2 alloys and CoFe2O4, the electronic conductivity and the active sites, and then the electrochemical performance of OER.