Interface-induced Fe-rich NixFe3-xO4 electrode for efficient oxygen evolution at high current densities

Utilizing renewable electricity to obtain “green” hydrogen is challenging due to the deterioration of active site activity and mass transfer capabilities at high current densities. Herein, a unique Fe-rich Ni x Fe 3−x O 4 @CP (Fe-NFC) self-supported electrode, directed by a special deep eutectic solvent (DES)-philic interface on the carbon paper (CP) collector, is developed. The Fe-NFC electrode exhibits high intrinsic catalytic activity and a stable catalyst-collector interface, enhancing oxygen evolution reaction (OER) activity and stability at elevated current densities. The regulated electronic structure of Fe-NFC is ascribed to the unique DES-philic carbon directing effect, which optimizes the adsorption energy of intermediates to further accelerate the O 2 formation during the OER process. The catalyst-collector interface also improves the mass transfer, which is favorable for the OER process at high current densities. Fe-NFC achieves a low OER overpotential of 360 mV at 1.5 A cm −2 and maintains stability for over 100 h. This work demonstrates the effectiveness of DES-interfaced engineering in optimizing active site structures and highlights the critical role of mass transport in OER at high current densities, offering a new direction for designing advanced functional materials for other gas evolution reactions.