Investigation on the Distinct Catalytic Origin of Nickel-Iron Sulfides/Selenides Oxygen Evolution Electrocatalyst

Abstract

Nickel-iron based electrocatalysts are efficient oxygen evolution reaction (OER) catalysts and their oxidative transition is widely reported in alkaline water splitting. However, the distinct catalytic origin governing their different catalytic performance is still unclear. Herein, NiFe chalcogenides, NixFe1−xSe and NixFe1−xS, are prepared, and their distinct OER performance and activity origin are comparatively investigated. NixFe1−xSe is found exhibits excellent OER electrocatalytic activity in 1 M KOH with an overpotential of 165 mV at 10 mA cm−2, outperforms that of NixFe1−xS (197 mV). Meanwhile, excellent stability performance is also achieved by NixFe1−xSe in anion exchange membrane water electrolyzer under high current density condition. Experimental analysis reveals that the high intrinsic activity of NixFe1−xSe is originated from the in-situ generated Se-doped γ-NiOOH species, whereas NixFe1−xS is converted into NiO/α-FeOOH during OER. Theoretical calculations show that, compared with NiO/α-FeOOH, Se/γ-NiOOH exhibits a higher degree of electron localization conducive to the stability of the Se/γ-NiOOH electronic structure, faster electron transfer, and favorable adsorption of reaction intermediates. The latter can effectively promote the transformation of *O into *OOH rate-controlling step, thereby exhibiting improved OER performance. These results provide new insights on the distinct catalytic origin of high efficiency NiFe-based OER electrocatalysts.