On the Controlled Loading of Single Platinum Atoms as a Co-Catalyst on TiO₂ Anatase for Optimized Photocatalytic H₂ Generation.

Abstract

Single-atom (SA) catalysis is a novel frontline in the catalysis field due to the often drastically enhanced specific activity and selectivity of many catalytic reactions. Here, an atomic-scale defect engineering approach to form and control traps for platinum SA sites as co-catalyst for photocatalytic H₂ generation is described. Thin sputtered TiO₂ layers are used as a model photocatalyst, and compared to the more frequently used (001) anatase sheets. To form stable SA platinum, the TiO₂ layers are reduced in Ar/H₂ under different conditions (leading to different but defined Ti³⁺ -O_v surface defects), followed by immersion in a dilute hexachloroplatinic acid solution. HAADF-STEM results show that only on the thin-film substrate can the density of SA sites be successfully controlled by the degree of reduction by annealing. An optimized SA-Pt decoration can enhance the normalized photocatalytic activity of a TiO₂ sputtered sample by 150 times in comparison to a conventional platinum-nanoparticle-decorated TiO₂ surface. HAADF-STEM, XPS, and EPR investigation jointly confirm the atomic nature of the decorated Pt on TiO₂ . Importantly, the density of the relevant surface exposed defect centers-thus the density of Pt-SA sites, which play the key role in photocatalytic activity-can be precisely optimized.