Remarkable enhancement of the alkaline oxygen evolution reaction activity of NiCo2O4 by an amorphous borate shell

Abstract

It is highly desirable but still a challenging task to find a simple, fast and straightforward method to greatly improve the alkaline oxygen evolution reaction (OER) performance of a NiCo₂O₄ catalyst. In this communication, we demonstrate that developing an amorphous borate shell on a NiCo₂O₄ surface can boost its OER activity in alkaline media. As a 3D catalyst electrode, a NiCo₂O₄@Ni–Co–B nanoarray on carbon cloth needs an overpotential of only 270 mV to achieve a geometrical catalytic current density of 10 mA cm⁻² in 1.0 M KOH, which is 100 mV less than that for a NiCo₂O₄ nanoarray. Notably, this electrode also demonstrates strong electrochemical durability, maintaining its activity for at least 100 h. The superior activity of NiCo₂O₄@Ni–Co–B is attributed to the amorphous Ni–Co–B shell on NiCo₂O₄ favoring the in situ electrochemical generation of more active species during water oxidation.