Single Phase Trimetallic Spinel CoCr_xRh_2‐xO₄ Nanofibers for Highly Efficient Oxygen Evolution Reaction under Freshwater Mimicking Seawater Conditions

Abstract Electrochemical water splitting is a promising pathway for sustainable oxygen production in terms of energy conversion. Seawater electrolysis, especially, is a sustainable approach to carbon‐neutral energy conversion without reliance on freshwater; however, extreme corrosion of anodic electrode caused by highly corrosive Cl⁻ is a main challenge of seawater oxidation. To address this issue, herein, nanofibers of trimetallic spinel CoCr_xRh_2‐xO₄ with various composition ratios are prepared for highly sustained water oxidation electrocatalysis. Among a series of CoCr_xRh_2‐xO₄, CoCr_0.7Rh_1.3O₄ nanofibers exhibit excellent electrocatalytic activity for oxygen evolution reaction (OER): the highest mass activity, the lowest overpotential at 10 mA cm⁻² and the smallest Tafel slope with robust long‐term stability under alkaline electrolyte. In addition, CoCr_0.7Rh_1.3O₄ nanofibers deliver better OER performances in simulated seawater than a commercial benchmark catalyst (IrO₂ nanoparticles), demonstrating that feasibility of alkaline seawater electrolysis with CoCr_0.7Rh_1.3O₄ nanofibers as an OER electrocatalyst.