Critical removal of surface carbonates on -Al2O3 to enhance nucleation of Pt atomic layer deposition

It is crucial to attain a sufficient surface distribution density of metal nanoparticles to achieve high catalytic performance in oxide-supported metal catalysts. Atomic layer deposition (ALD) is a powerful technique for preparing supported nanocatalysts to precisely regulate the metal particle size, structure and distribution in nanoscale. Not only suitable ALD deposition parameters, but also supports with sufficient ALD nucleation sites on the surface are required when using ALD to synthesize supported metal particles with ultrafine size and ultrahigh density. How to regulate the surface nucleation sites to acquire metal nanoparticles with high surface density and elucidating the mechanism are of great importance. Herein, we present a simple thermal treatment approach to activate the surface of gamma-Al2O3, significantly enhancing the Pt loading and the density of Pt nanoparticles compared to raw gamma-Al2O3 under identical deposition conditions. Detailed mechanism investigations reveal that removing carbonates on the surface of gamma-Al2O3 during thermal treatment induces the generation of isolated -OH groups, which are verified to be nucleation sites of Pt ALD. The increase in the number of isolated -OH and its high reactivity towards anchoring Pt precursor molecules in ALD reaction both contribute to a high density of Pt nanoparticles. This work provides a novel approach to promote Pt ALD nucleation on the surface of gamma-Al2O3 and an in-depth understanding of the mechanism for the nucleation promotion, which can be applied to other oxide supports.