Dual‐Doped CoFe Hydroxide Through Chromium and Sulfur Incorporation for Efficient Oxygen Evolution in Alkaline Seawater Electrolysis

The oxygen evolution reaction (OER) remains a critical kinetic bottleneck in water electrolysis for sustainable hydrogen production, necessitating the development of efficient and durable electrocatalysts. Herein, a sulfur-incorporation strategy is employed to regulate the activity and stability of CoFeCr hydroxide toward OER in alkaline and seawater environments. Sulfur-incorporated CoFeCr hydroxide (S-CoFeCr-OH) is synthesized via a two-step hydrothermal-sulfurization process, which preserves the nanosheet architecture while enabling uniform sulfur incorporation into the hydroxide lattice without forming inactive sulfide phases. As a result, S-CoFeCr-OH delivers a low overpotential of 289 mV at 10 mA cm^-2 with a reduced Tafel slope of 56.8 mV dec^-1, accompanied by accelerated charge-transfer kinetics, an enlarged electrochemical surface area, and enhanced intrinsic activity as evidenced by current densities normalized to the electrochemically active surface area. Notably, the catalyst exhibits excellent durability over 40 h and strong tolerance to chloride-containing environments. This behavior is attributed to sulfur-derived anionic surface modulation acting synergistically with chromium-mediated electronic and structural stabilization, enabling sustained OER performance under alkaline seawater conditions. These findings highlight the effectiveness of a cooperative cation-anion codoping strategy that integrates sulfur-mediated anionic modulation with multimetal hydroxide chemistry, providing a viable design principle for robust and earth-abundant OER electrocatalysts for practical seawater electrolysis.