Valence State Regulated Nickel Iron Layered Double Hydroxides by Amine Intercalation as Efficient Electrocatalysts for Seawater Oxidation

The manipulation of the valence state along with electronic spin configurations of metal sites in NiFe layered double hydroxides has been recognized as a feasible strategy to boost intrinsic electrocatalytic oxygen evolution reaction activity. In this study, high-valence Ni³⁺ with a low-spin configuration has been introduced in NiFe layered double hydroxide nanosheets by facile amine intercalation in the interlayers. The influence of such valence state regulations with a favorable electronic low-spin configuration of Ni³⁺ was found to be very impactful toward an efficient water oxidation mechanism. Certainly, the Jahn–Teller distortion associated with the low-spin electronic configuration instigates a defect center often known to be an active center leading to surface reconstruction beneficial for OER activity. The electrocatalyst exhibited an outstanding OER activity with an ultralow overpotential of 216 mV to achieve a 20 mA cm^–2 current density and a lower Tafel slope value of 50 mV dec^–1 in alkaline media. The ability of the electrocatalyst was further explored toward seawater oxidation, demonstrating it to be a potential candidate with an outstanding durability of over 160 h at a high current density of 500 mA cm^–2 in alkaline real seawater.