Surface metal-EDTA coordination layer activates NixFe3-xO4 spinel as an outstanding electrocatalyst for oxygen evolution reaction.

ABSTRACT

Nickel-iron oxides are competitive electrocatalysts for oxygen evolution reaction, but their practical applications are restricted by the less-than-desirable intrinsic activity and working stability. To tackle the challenge, surface coordination chemistry is applied to the nickel-iron oxides through a complex-assisted in-situ crystal growth strategy. The ethylenediaminetetraacetate (EDTA) coordinated NixFe3-xO4 (NixFe3-xO4-EDTA) is prepared by a simple one-pot hydrothermal process. The coordinated EDTA molecules can deeply alter the surface coordination structure of the NixFe3-xO4. The NixFe3-xO4-EDTA demonstrates outstanding intrinsic activity towards oxygen evolution reaction, requiring only a small overpotential of 180 mV to reach 10 mA cm-2 in 1.0 M KOH. Moreover, the NixFe3-xO4-EDTA exhibits extremely stable long-term working stability. Density functional theory calculations show that the highly enhanced intrinsic activity is attributed to the surface coordinated EDTA-induced favorable electronic structure and coordination environment, which tunes the adsorption strength of the intermediates and optimizes the energetics of the elementary steps, while the high stability is ascribed to the strong coordination ability of EDTA.