Direct characterization of interface sites in Au/TiO2 catalysts prepared using atomic layer deposition

Summary

Au/TiO₂ catalysts were developed by growing thin titania films via atomic layer deposition (ALD) on a high-surface-area silica support (SBA-15) to test the effect of both the film thickness and the order of deposition. The physical characteristics of both titania and gold phases were similar in all catalysts except for the thickness of the former, which was varied by using one to four ALD cycles. However, it was found that if the titania film is deposited after the gold nanoparticles, it partially covers the metal surface and reduces the catalytic activity (compared with the case where the gold is deposited last). In those samples, X-ray photoelectron spectroscopy (XPS) data showed a large fraction of partially positively charged Au atoms, and titration of surface sites with CO and infrared absorption spectroscopy detection identified a large fraction of low-coordination Ti sites, with a surface coverage that increased with titania film thickness.