Metal hybridization in dilute-alloy catalysts promotes sintering resistance by decreasing surface mobility

Dilute-metal-alloy nanoparticles exhibit enhanced catalytic performance compared with monometallic nanoparticles for many reactions. Anecdotal reports indicate that very dilute alloying can also slow the sintering rates of supported nanoparticles, although this has not been rigorously assessed and cannot be explained using bulk descriptors such as metal melting temperature. Here we utilize methanol synthesis reactivity, microscopy and in situ spectroscopy measurements to demonstrate that 1 atom% Pt addition to ~1-2-nm-diameter Cu (Pt₁Cu₁₀₀) nanoparticles supported on SiO₂ dramatically decreases their sintering rates. Minimal sintering of Pt₁Cu₁₀₀ nanoparticles is observed during aging in H₂ up to 700 °C versus 500 °C for Cu nanoparticles. Scanning tunnelling microscopy reveals that the addition of 0.01 monolayer of Pt to a Cu(110) surface decreases the detachment rate of undercoordinated atoms, demonstrating that dilute dopants can locally decrease the rate of the first step in nanoparticle sintering. Density functional theory calculations quantify the stabilization and predict other sinter-resistant dilute alloys. We find that the degree of host-dopant d-state hybridization correlates with decreased surface mobility, providing a mechanistic framework for designing sinter-resistant catalysts.