Advanced Photocatalysts: Pinning Single Atom Co-Catalysts on Titania Nanotubes

Single atom (SA) catalysis, over the last 10 years, has become a forefront in heterogeneous catalysis, electrocatalysis, and most recently also in photocatalysis. Most crucial when engineering a SA catalyst/support system is the creation of defined anchoring points on the support surface to stabilize reactive SA sites. Here, a so far unexplored but evidently very effective approach to trap and stabilize SAs on a broadly used photocatalyst platform is introduced. In self-organized anodic TiO2 nanotubes, a high degree of stress is incorporated in the amorphous oxide during nanotube growth. During crystallization (by thermal annealing), this leads to a high density of Ti3+-O-v, surface defects that are hardly present in other common titania nanostructures (as nanoparticles). These defects are highly effective for SA iridium trapping. Thus a SA-Ir photocatalyst with a higher photocatalytic activity than for any classic co-catalyst arrangement on the semiconductive substrate is obtained. Hence, a tool for SA trapping on titania-based back-contacted platforms is provided for wide application in electrochemistry and photoelectrochemistry. Moreover, it is shown that stably trapped SAs provide virtually all photocatalytic reactivity, with turnover frequencies in the order of 4 x 10(6) h(-1) in spite of representing only a small fraction of the initially loaded SAs.

Automated summary

Single atom catalysis has become a leading field in heterogeneous catalysis, electrocatalysis, and more recently in photocatalysis. A novel approach to trap and stabilize single atoms on a widely used photocatalyst platform has been introduced, showing higher photocatalytic activity compared to classic co-catalyst arrangements. Stably trapped single atoms provide the majority of photocatalytic reactivity, with high turnover frequencies despite being a small fraction of the initial load.