Fractal Behavior of Nanostructured Pt/TiO[sub.2] Catalysts: Synthesis, Characterization and Evaluation of Photocatalytic Hydrogen Generation

The fractal characterization of supported nanoparticles is a useful tool for obtaining structural and morphological information that strongly impacts catalytic properties. We have synthesized and characterized Pt supported on TiO[sub.2] nanostructures. Triblock copolymers with thermosensitive properties were used as templating agents during the synthesis process. In addition to the several techniques used for the characterization of the materials, we carried out fractal analysis. The prepared materials showed a reduction in the band gap of TiO[sub.2] from 3.44 to 3.01 eV. The extended absorption in the 500–700 nm regions is mostly attributed to the presence of supported Pt nanoparticles. The ability of the nanostructured Pt/TiO[sub.2] catalysts to generate H[sub.2] in an aqueous solution was evaluated. The test reaction was carried out in the presence of methanol, as a hole scavenger, under simulated solar light. Pt/TiO[sub.2]-3TB shows the highest rate of H[sub.2] (4.17 mmol h[sup.−1] g[sub.cat] [sup.−1]) when compared to Pt/TiO[sub.2]-0TB (3.65 mmol h[sup.−1] g[sub.cat] [sup.−1]) and Pt/TiO[sub.2]-6TB (2.29 mmol h[sup.−1] g[sub.cat] [sup.−1]) during simulated solar light irradiation. Pt/TiO[sub.2]-3TB exhibits a more structured organization (fractal dimensions of 1.65–1.74 nm at short scales, 1.27–1.30 nm at long scales) and a distinct fractal behavior. The generation of hydrogen via photocatalysis can be linked to the fractal characteristics.