Electronic Structure Engineering of Sub‐1 nm Ni(OH)2 Nanowires Through Fe Incorporation in Polyoxometalates for Superior Water Oxidation

Abstract NiFe‐based electrocatalysts have shown considerable promise as outstanding candidates to replace the Ru/Ir‐based oxides for the oxygen evolution reaction (OER). However, conventional NiFe‐based materials suffer from low active‐site density and poorly defined structures, thus hindering elucidation of Fe's role in catalytic performance. Herein, a facile solvothermal strategy is reported for the fabrication of 1D sub‐1 nm NiFe‐based nanowires, constructed through the self‐assembly of Fe‐substituted polyoxometalate (PMo 11 Fe) clusters with Ni(OH) 2 . The resulting Ni(OH) 2 ‐PMo 11 Fe sub‐1 nm hybrid nanowires (SHNWs) form an ordered end‐to‐end configuration, as confirmed by molecular dynamics (MD) simulations. Benefiting from their unique 1D sub‐1 nm architecture and precisely controlled composition, these SHNWs demonstrate remarkable OER performance, requiring an overpotential of only 229 mV to achieve a current density of 10 mA cm⁻ 2 , along with excellent long‐term stability. Experimental analyses and density functional theory (DFT) calculations reveal that Ni serves as the primary active site, forming Ni─OOH intermediates during OER, while Fe modulates the electronic structure of Ni, thereby enhancing the overall catalytic activity. This work highlights the potential of structurally and compositionally well‐defined NiFe‐based catalysts to address the challenges of low OER activity, while offering critical insights into the synergistic role of Fe in NiFe systems.