Defect engineering of mesoporous nickel ferrite and its application for highly enhanced water oxidation catalysis

Abstract

Spinel nickel ferrite (NiFe2O4) emerges as a promising low-cost catalyst for water splitting but it usually shows low catalytic activity because of its limited number of active sites and poor conductivity. For the first time, herein we have successfully overcome its weaknesses using defect engineering approach by creating oxygen vacancies in NiFe2O4. The existence of oxygen vacancy not only shifts up the d-band center, strengthens the adsorption of H2O, and thus provides more active catalytic sites, but also tunes the electron configuration and creates massive number of defective donor states in the band gap to facilitate charge transfer processes. The optimal defective catalyst showed significantly enhanced catalytic OER performance with an OER overpotential as low as 0.35 V at 10 mA cm−2 and a Tafel slope of only ∼40 mV dec−1. Moreover, the impressive specific mass and area current density of 17.5 A g−1 and 0.106 A m−2 at 1.58 V vs. RHE have been achieved, which are ∼23 and ∼36 times higher than that of defect-free counterpart, respectively.