Octahedral Coordinated Trivalent Cobalt Enriched Multimetal Oxygen‐Evolution Catalysts

Abstract Octahedral coordinated trivalent cobalt cations (Co_Oh³⁺) in metal oxyhydroxides are highly active catalytic sites for the oxygen evolution reaction (OER), a critical bottleneck for efficient water splitting; however, previous synthetic methods have limited control over these sites. Herein, a scalable electrodeposition method coupled with in situ oxidation to produce amorphous Co–Fe–W trimetallic oxyhydroxides enriched with Co_Oh³⁺ is developed. X‐ray absorption, in operando spectroscopic analysis, and computational studies reveal that 72% of the Co atoms are present in Co_Oh³⁺ sites. Fe and W synergistically affect the electronic structure of Co and provide a favorable coordination environment. The Co–Fe–W oxyhydroxide exhibits superior OER catalytic performance with an impressive turnover frequency of 1.96 s⁻¹ at an overpotential of 300 mV, a low Tafel slope of 32 mV dec⁻¹, and small activation energy of 53 kJ mol⁻¹ in alkaline electrolyte. The catalyst directly deposited on Ni foams can serve as a robust OER electrode in two‐electrode water electrolyzers; they deliver a current density of 100 mA cm⁻² at a small overpotential of 234 mV in alkaline electrolyte with excellent durability under 100 mA cm⁻² over 120 h. These catalysts are excellent for practical water splitting applications.