Oxygen-vacancy-mediated electron localization at the nickel sites in nickel/iron layered double hydroxide towards efficient oxygen evolution reaction

Abstract

Nickel/iron layered double hydroxide (NiFe-LDH) represents a promising electrocatalyst for the challenging oxygen evolution reaction (OER), yet the precise role of iron (Fe) in enhancing its activity remains unclear. Herein, we conduct a comprehensive investigation aimed at unraveling the influence of Fe incorporation on the atomic environments and electronic structure of NiFe-LDH, with the ultimate goal of establishing a correlation between these factors and elucidating the mechanisms by which Fe amplifies the OER performance. Our findings reveal that Fe dopants induce weakening of the nickel (Ni)-oxygen (O) coordination, and then generate abundant oxygen vacancies (O_V), which can mediate the electron transfer from Fe to Ni and finally result in electron localization at the Ni centers. The electron localization around Ni leads to the creation of a new energy level near the Fermi level and the formation of an electron-rich structure, resulting in a favorable electronic conductivity and reaction kinetics. The optimal NiFe-LDH sample exhibits an extraordinary electrocatalytic performance, requiring ultra-low overpotentials of only 189 and 248 mV to achieve current densities of 10 and 100 mA cm⁻², respectively, in a 1.0 M KOH electrolyte. The comprehensive understanding obtained from this study can guide future design of high-performance NiFe-LDH-based electrocatalysts.