NiFe-Layered Double Hydroxides Modified with Co–Mo Nitride for the Oxygen Evolution Reaction in Seawater

Abstract

Direct electrolysis of seawater offers a promising pathway for sustainable hydrogen production while avoiding the issues caused by freshwater shortages. However, the sluggish four-electron transfer kinetics and the competitive adsorption of Cl^– ions of the oxygen evolution reaction (OER) during seawater electrolysis remain as key challenges in designing effective catalysts. Herein, leveraging the electron-absorbing properties of molybdenum cobalt nitride (CoN/Mo₂N) to modulate the electronic structure of nickel–iron layered double hydroxide (NiFe-LDH), a nanoscale hierarchical heterostructure of NiFe-LDH coated on CoN/Mo₂N (CoN/Mo₂N/LDH) was engineered to achieve highly efficient OER. Operando electrochemical impedance spectroscopy reveals that the heterointerface facilitates charge transport kinetics. Additionally, charge density analysis and adsorption energy calculations confirm that the NiFe-LDH preferentially adsorbs OH^– over Cl^– in alkaline seawater. The CoN/Mo₂N/LDH nanostructure requires only 249 mV overpotential to achieve 500 mA·cm^–2 in 6 M KOH + seawater, maintaining 94.8% of its initial activity over 10 days of continuous operation. This work elucidates the electron-absorption-driven modulation of electronic structures in nitride-regulated LDH nanomaterials, enabling their application in industrial-scale seawater electrolysis. The tailored nanoscale design achieves simultaneous high-efficiency oxygen evolution and exceptional stability, advancing scalable green hydrogen production from seawater.