Synergistic Bifunctional Sites Catalysis in Atomically Mixed Ir x Os1− x Nanoparticles for Efficient NO Reduction by CO

The development of cost-effective alternatives to rhodium for catalytic NO reduction by CO remains urgent and challenging. Here, we report the synthesis of atomically mixed IrxOs1−x solid-solution nanoparticles across the full compositional range. The optimized Ir0.4Os0.6/γ-Al2O3 catalyst achieved a temperature at 50% conversion of 214 °C, far surpassing those of monometallic Ir (300 °C) and Os (266 °C) and rivaling a commercial Rh benchmark. Their activities exhibited a clear volcano-type dependence on the Ir content. Combining X-ray photoelectron spectroscopy, in situ Fourier transform infrared spectroscopy, and density functional theory calculations, we revealed a synergistic bifunctional site mechanism, where Os sites promoted NO dissociation, while Ir sites enabled fast N−N coupling and CO oxidation, with electron transfer from Os to Ir further facilitating N2 formation. This work demonstrated solid-solution alloying as an effective strategy for designing high-performance, low-cost NOx-removal catalysts.