Semicrystalline Nickel Cobalt Tungstate Solid-Solution for Enhanced Electrocatalytic Oxygen Evolution Activity in Alkaline Media

The present study features a compositional tuning strategy to fabricate semicrystalline nickel cobalt tungstates in gram-scale using a one-step coprecipitation method. Among all samples, the results indicate that the 1:3 molar ratio of Ni-to-Co (N 1 C 3 W) catalyst exhibits the optimal oxygen evolution reaction (OER) activity in 1 M KOH. Structural analysis reveals that N 1 C 3 W forms a solid-solution comprising a unique blend of amorphous and crystalline phases, which result in a high electrochemical active surface area of ∼102.0 m 2 g –1, significantly greater than its individual crystalline or amorphous counterparts. This hybrid structure enhances the exposure of active sites to the electrolyte, facilitating improved electrocatalytic performance. N 1 C 3 W manifests promising alkaline oxygen evolution activity, requiring only ∼301 mV overpotential to achieve 10 mA cm –2, along with a low Tafel slope of ∼44 mV dec –1 as determined by rotating disk electrode (RDE) evaluation. The N 1 C 3 W catalyst outperforms commercial IrO 2 in terms of mass transport, charge transfer kinetics, and stability. These findings demonstrate that semicrystalline nickel cobalt tungstates are promising and durable candidates for enhancing OER performance in alkaline electrolyzers.