Optimized Pt Single Atom Harvesting on TiO₂ Nanotubes-Towards a Most Efficient Photocatalyst

In the present work the authors show that anodic TiO₂ nanotubes (NT) show excellent harvesting properties for Pt single atoms (Pt SAs) from highly dilute Pt solutions. The tube walls of anodic nanotubes, after adequate annealing to anatase, provide ample of suitable trapping sites-that is, surface Ti³⁺ -O_v (O_v : oxygen vacancy) defects that are highly effective to extract and accumulate Pt in the form of SAs. A saturated (maximized) SA density can be achieved by an overnight immersion of a TiO₂ NT layer to a H₂ PtCl₆ solution with a concentration that is as low as 0.01 mm Pt. Such TiO₂ NTs with surface trapped Pt SAs provide a maximized high activity for photocatalytic H₂ generation (reaching a turnover frequency (TOF) of 1.24 × 10⁶ h^-1 at a density of 1.4 × 10⁵ Pt atoms µm^-2 )-a higher loading with Pt nanoparticles does not further increase the photocatalytic activity. Overall, these findings show that anodic TiO₂ nanotubes provide a remarkable substrate for Pt extraction and recovery from very dilute solutions that directly results in a highly efficient photocatalyst, fabricated by a simple immersion technique.