Thin Porous Alumina Sheets as Supports for Stabilizing Gold Nanoparticles

Thin porous alumina sheets have been synthesized using a lysine-assisted hydrothermal approach resulting in an extraordinary catalyst support that can stabilize Au nanoparticles at annealing temperatures up to 900 degrees C. Remarkably, the unique architecture of such an alumina with thin sheets (average thickness similar to 15 nm and length 680 nm) and rough surface is beneficial to prevent gold nanoparticles from sintering. HRTEM observations clearly showed that the epitaxial growth between Au nanoparticles and alumina support was due to strong interfacial interactions, further explaining the high sinter-stability of the obtained Au/Al2O3 catalyst. Consequently, despite calcination at 700 degrees C, the catalyst maintains its gold nanoparticles of size predominantly 2 +/- 0.8 nm. Surprisingly, catalyst annealed at 900 degrees C retained the highly dispersed small gold nanoparticles. It was also observed that a few gold particles (6-25 nm) were encapsulated by an alumina layer (thickness less than 1 nm) to minimize the surface energy, revealing a surface restructuring of the gold/support interface. As a typical and size-dependent reaction, CO oxidation is used to evaluate the performance of Au/Al2O3 catalysts. The results obtained demonstrated Au/Al2O3 catalyst calcined at 700 degrees C exhibited excellent activity with a complete CO conversion at similar to 30 degrees C (T-100% = 30 degrees C), and even after calcination at 900 degrees C, the catalyst still achieved Its T-50% at 158 degrees C. In sharp contrast, Au catalyst prepared using conventional alumina support shows almost no activity under the same preparation and catalytic test conditions.