Gas-pressure-assisted strategy for precise control of palladium-based nanoparticle sizes: Unveiling size effects on methanol oxidation activity.

Understanding the relationship between catalyst particle size and activity is crucial for developing efficient catalytic systems. However, the size-dependent behavior of Pd-based alloy catalysts remains poorly understood, requiring a comprehensive investigation. This study presents a straightforward and effective gas-pressure-assisted heat-treatment method that allows precise control over the particle sizes of various Pd-based catalysts, including Pd, Pd3Fe, Pd3Co, Pd3Ni, and Pd3Cu. Our findings demonstrate that high pressure significantly inhibits nanoparticle sintering by increasing energy barriers for both metal atomic diffusion and nanocluster migration. A linear relationship has been established between average particle size and applied gas pressure. Specifically, this method was employed to synthesize Pd3Fe nanoparticles (NPs) with an average particle size ranging from 2.8 to 6.9 nm. Furthermore, we explored the size effect of Pd3Fe/C in the methanol oxidation reaction (MOR). The mass activity (MA) of the catalyst exhibited a volcano-shaped trend as particle size decreased. Notably, the Pd3Fe/C-7 MPa catalyst with a particle size of 3.9 nm demonstrated superior MA compared to other samples within this range of sizes tested in this study. This work offers a valuable approach for systematically studying the size effect on catalytic performance, which aids researchers in designing high-performance catalytic materials.