Redispersion of Gold Multiple-Twinned Particles during Liquid-Phase Hydrogenation

Controlling the particle size of supported metal catalysts is essential to achieving active, selective, and stable catalysts. High-resolution electron microscopy has revealed that large Au particles (∼8 nm), supported on titania and if multiple-twinned, broke up into small particles (2–3 nm) during liquid-phase hydrogenation. Multiple-twinned Au particles, obtained after gas-phase reduction of as-prepared Au/TiO 2 at elevated temperature, break up into smaller particles. EXAFS confirmed that the multiple-twinned particles were agglomerates of smaller particles. In contrast, calcination caused a strong interaction between Au and titania and the formation of mainly single crystalline Au particles (4 to 5 nm), which were relatively stable during liquid-phase hydrogenation. Reduction and calcination lead to gold particles that are fundamentally different.