Synergistic spin effects in medium-entropy Ni-Fe-Mn-Ce oxyhydroxides for seawater oxidation

Efficient and durable oxygen evolution reaction (OER) electrocatalysis is essential for advancing sustainable seawater electrolysis. In this work, a high-performance Ni-Fe-Mn-Ce medium-entropy oxyhydroxide is constructed via in situ electrochemical reconstruction strategy for the OER. Guided by density functional theory (DFT), the effects of eight candidate fourth-metal elements (Al, Ce, Co, Cr, Cu, Sn, Zn, or Zr) on the electronic structure and reaction energetics of the NiFeMn(O)OH matrix are comprehensively investigated, revealing the unique advantages of Ce in optimizing intermediate adsorption energies and lowering the theoretical overpotential. The catalyst requires an overpotential of only 183 mV at 10 mA cm^-2 in 1 M KOH, while maintaining a low overpotential of 224 mV in alkaline seawater, along with excellent resistance to Cl^- corrosion. Operando spectroscopic characterizations reveal dynamic valence evolution and charge redistribution among Ni⁴⁺, Fe³⁺, and Ce³⁺/Mn²⁺ species, which contribute to stabilizing intermediate adsorption and promoting electron transfer. Further electronic structure analysis demonstrates a favorable d-band center near the Fermi level and pronounces spin polarization in the medium-entropy system, which synergistically enhance OER kinetics. This work highlights the potential of entropy engineering combined with theoretical guidance in the development of advanced multi-metallic electrocatalysts for efficient seawater splitting.