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 (N1C3W) catalyst exhibits the optimal oxygen evolution reaction (OER) activity in 1 M KOH. Structural analysis reveals that N1C3W 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 m2 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. N1C3W 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 N1C3W catalyst outperforms commercial IrO2 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.