Se-vacancy induced structural reconstruction of iron nickel selenium nanosheets for efficient and durable electrocatalytic alkaline water and seawater oxidation†

Abstract

The development of efficient and stable catalysts for the oxygen evolution reaction (OER) is critical for the progress of electrocatalytic alkaline water and seawater hydrogen production. Herein, we report Se-vacancy-rich Fe-doped NiSe (V_Se-FeNiSe/NFF) nanosheets with remarkable OER performance in both alkaline and seawater media. It is revealed that the Se vacancies significantly promote structural reconstruction during the OER process, which facilitates the formation of highly active NiFeOOH and SeO₄²⁻ species, thus delivering exceptional catalytic activity and stability. Moreover, theoretical calculations reveal that introducing selenium vacancies upshifts the d-band center toward the Fermi level, facilitating electron excitation and interfacial charge transfer, while reducing the Gibbs free energy barrier of the rate-determining step. In alkaline media, they require an overpotential of 242 mV to achieve a current density of 100 mA cm⁻², with a low Tafel slope of 30 mV dec⁻¹ and robust stability over 500 h. Meanwhile, in seawater media, they just require an overpotential of 253 mV to achieve 100 mA cm⁻², with a Tafel slope of 35.5 mV dec⁻¹. Impressively, they could be operated stably for 100 h at 100 mA cm⁻². This work not only elucidates the roles of Se vacancies in the reconstruction of selenides during the OER process, but also offers meaningful insight into exploring advanced electrocatalysts for the OER in both alkaline water and seawater media.