Effect of substrate temperature on the structure and HOR activity of ALD-synthesized Ru nanoparticles for alkaline membrane exchange fuel cells

Ruthenium nanoparticles (Ru NPs) were synthesized on carbon supports using atomic layer deposition (ALD) to develop high-performance, non-platinum catalysts for the hydrogen oxidation reaction (HOR) toward anion exchange membrane fuel cells (AEMFCs). The influence of substrate temperature on the structure and catalytic activity of Ru NPs was systematically investigated. Ru deposition was carried out at 250-350 °C using an ALD system, yielding Ru NPs with uniform distribution and tunable crystallinity. Characterization by TEM, XRD, and XPS revealed that higher deposition temperatures led to increased crystallinity and Ru loading, while certainly high temperatures (>= 350 °C) produced particle agglomeration and non-uniform growth. Among them, the catalyst synthesized at 300 °C exhibited the most favorable properties, ∼2.2 nm particles with partial crystallinity and roughened surfaces resulting in the high electro-chemical surface area (ECSA), optimal hydrogen binding energy (HBE), and superior HOR activity. Electrochemical analysis confirmed that ALD Ru catalyst at 300 °C outperformed commercial Ru/C in both mass and specific activities. These findings highlight the critical role of temperature-controlled ALD in tailoring the structure-activity relationship of Ru catalysts, providing a scalable pathway toward efficient and durable AEMFC anode materials.