Modulating Photogenerated Electron Transfer and Hydrogen Production Rate by Controlling Surface Potential Energy on a Selectively Exposed Pt Facet on Pt/TiO₂ for Enhancing Hydrogen Production

Abstract

We reported the results of the modulation of photogenerated electrons transfer and photocatalytic hydrogen evolution behaviors of Pt/TiO2 photocatalyst via controlling surface potential energy on a selectively exposed Pt facet for a highly efficient photocatalytic hydrogen generation from water. By photosensitization using Eosin Y as an antenna molecule, distinct differences in photocatalytic hydrogen evolution performances over Pt/TiO2 with different exposed facets ({100}, {100/111}, and {111}) of Pt under visible light irradiation were observed. Pt{111}/TiO2 photocatalyst exhibited a much higher photocatalytic hydrogen generation activity than those of Pt{100}/TiO2 and Pt{100/111}/TiO2. As evidenced by photoluminescence spectra, photoelectrochemical characterizations, electrochemical impedance spectra (EIS) measurements, and Mott–Schottky measurements, Pt nanoparticles with exposed {111} facets were more effective in trapping the electrons from the conduction band of TiO2 than that of {100} facets due to their higher Fermi level of {111} facets. In addition, Pt{111}/TiO2 exhibited much lower apparent activation energy for hydrogen generation than those of other samples because the fraction of Pt atoms located on edges and corners on Pt{111} nanoparticles was higher than that on Pt{100} nanoparticles. Therefore, Pt{111}/TiO2 can provide more reaction sites for water reduction. In addition, Pt{111}/TiO2 exhibits much lower apparent activation energy or hydrogen generation than those of other samples because this catalyst can provide more reaction sites for water reduction. The formation of hydrogen via recombination between chemisorbed H atoms is more likely to occur over Pt{111} facets because of the reasonable transition state geometry of chemisorbed H on Pt{111} facets. This study discloses the facet-dependent effect of noble-metal cocatalyst on semiconductors in photocatalytic water reduction and will give an insight into design and synthesis of high-efficient metal/semiconductor hybrid photocatalysts.