Solid-State Approach to Bimetallic IrRu/C Catalysts Tuning toward Boosted Oxygen Evolution in Acidic Media

Abstract

Metallic iridium (Ir) and ruthenium (Ru) are among the most active OER electrocatalysts in acidic media. Alloying Ir and Ru can enhance catalytic performance while reducing costs. Here, we introduce a scalable solid-state synthesis method to produce nanostructured IrRu semialloy on a high-porosity carbon substrate for efficient OER. This thermal-based approach offers a straightforward and cost-effective alternative to conventional methods and, therefore, eliminates complex procedures, organic solvents, and capping agents while ensuring fine nanoparticle (NP) dispersion. Electrochemical studies show that Ru-rich samples achieve high initial activity, while Ir-rich samples demonstrate superior stability in 0.1 M HClO₄. Notably, Ir_0.5Ru_0.5/C and Ir_0.25Ru_0.75/C electrodes achieved mass activities of 1605 and 2494 A g_metal^-1 at 1.65 V (versus RHE)., respectively. Among them, Ir_0.5Ru_0.5/C retained 70% of its initial OER performance, outperforming commercial IrO₂ (53%) and other as-prepared catalysts in terms of stability. HAADF-STEM analysis revealed that Ir_0.5Ru_0.5/C has the finest particle size distribution, with the highest fraction of sub-2 nm NPs. Theoretical calculations confirmed that *-OOH formation is the rate-determining step (RDS) for both catalysts of interest. The highest reaction energy for Ir_0.25Ru_0.75/C is 3.94 eV, whereas, for Ir_0.5Ru_0.5/C, it is 4.46 eV. This study demonstrates that solid-state synthesis enables the controlled design of highly active and stable IrRu catalysts and offers a promising approach for scalable OER catalyst production.