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.

"Dark Deposition" of Ag Nanoparticles on TiO2: Improvement of Electron Storage Capacity To Boost "Memory Catalysis" Activity

"Memory catalysis" (MC) studies have received appreciable attention recently because of the unique talent to retain the catalytic performance in the dark condition. However, the MC activity is still low owing to the relatively limited electron storage capacity of the present materials. Here, a TiO₂@Ag composite was synthesized by a "dark-deposition (DD)" method, which is based on the electron trap effect of TiO₂. Unlike traditional photodeposition (PD), an exploration of the morphology and chemical compositions of as-prepared samples shows that DD can inhibit the growth of Ag nanoparticles and the formation of Ag₂O, which greatly improve the electron storage capacity. We further demonstrated that the maximum electronic capacity was in the order of TiO₂@Ag-DD (1 μmol/mg) > TiO₂@Ag-PD (0.35 μmol/mg) > TiO₂ (0.11 μmol/mg). Moreover, the enhanced MC activity was confirmed by various degradation experiments. Especially, the use of TiO₂@Ag-DD as a round-the-clock catalyst for the degradation of multicomponent pollutants has also been achieved. This strategy opens a door for enhancing the MC activity and reveals that the coupling of photocatalysis and MC may provide a new opportunity for the continuous removal of pollutants in day and night. It also may be extended to other fields, such as energy storage and continuous disinfection.