Drastic Enhancement of Photocatalytic Activity of TiO2 Particles with Well-Defined Crystal Facets upon Deposition of Platinum
Christiane Adler a, Dariusz Mitoraj a, Radim Beranek a
a University of Ulm, Albert-Einstein-Allee 11, Ulm, Germany
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#SolFuel19. Solar Fuel Synthesis: From Bio-inspired Catalysis to Devices
Berlin, Germany, 2019 November 3rd - 8th
Organizers: Roel van de Krol and Erwin Reisner
Poster, Christiane Adler, 439
Publication date: 18th July 2019

Light-driven heterogeneous photocatalysis is one of the most promising low-cost methods for carrying out various useful redox transformations. However, typical semiconductor photocatalysts suffer from very low quantum efficiencies (few per cent) due to inefficient charge separation and fast recombination of photogenerated charge carriers. Apart from other approaches, two promising strategies for mitigating this problem consist in i) fabrication of photocatalysts with well-defined crystal facets,1 and ii) deposition of redox catalysts that should enhance the rate of interfacial redox reactions,2 whereby these strategies can be combined.3 However, the factors governing the photocatalytic activity of such engineered photocatalyst particles still need to be elucidated. In this work, we investigate the effect of facet-selective deposition of platinum nanoparticles onto anatase TiO2 crystals prepared by hydrothermal method in fluoride-containing solution.  We achieved a facet-selective photodeposition of metallic Pt nanoparticles on the “reductive” {101} facet of as-prepared (non-calcined) TiO2 anatase crystals. Notably, while the as-prepared TiO2 particles were completely inactive in photocatalytic degradation of 4-chlorophenol (4-CP) under UV irradiation, the deposition of Pt led to drastic enhancement of photocatalytic activity. Our mechanistic investigations suggest that the improvement is due to the enhancement of the reductive pathway (trapping of electrons and catalysis of oxygen reduction at Pt nanoparticles). Interestingly, Pt photodeposition on TiO2 crystals with low fluoride surface concentration (calcined at 450 °C) resulted in facet-nonselective deposition. This suggests that the selective deposition of Pt is a result of (001) surface blockage by fluoride, rather than by intrinsic directional facet-selective charge separation.

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