High-index facet NiFeB@H-NiFeBO core–shell nanowires for a highly efficient oxygen evolution reaction in water splitting

Abstract

Efficient electrocatalysts of non-precious metals are essential for advancing the oxygen evolution reaction (OER) in water splitting. In this study, we present a novel nanowire catalyst, comprising a NiFe borate shell grown along a high-index facet (HIF) that coats a NiFe-boride (NiFeB) core, denoted as NiFeB@H-NiFeBO. In situ and ex situ experimental calculations along with theoretical calculations reveal that the presence of the NiFeB nucleus reduces the surface energy of the HIF in the H-NiFeBO shell, promoting its directional growth along the HIF and enhancing the lattice oxygen oxidation mechanism (LOM) to boost the OER activity. Additionally, the NiFeB core stabilizes the *OO-V_O intermediates in the LOM pathway, enhances the reversibility of NiFeB@H-NiFeBO and averts structural collapse, thereby improving the long-term stability of the OER. The resulting NiFeB@H-NiFeBO catalyst demonstrates outstanding OER performance with a low overpotential of 212 mV at a current density of 100 mA cm⁻². Furthermore, the optimized catalyst delivers a low voltage of 1.52 V@1 A cm⁻² for 1000 h at 80 °C in an anion-exchange membrane water electrolyzer. This work presents a promising avenue for the design of efficient electrocatalysts for industrial water splitting applications.