Thiomolybdate [MoS] nanoclusters, as a molecular mimic of MoS edge sites, showed high efficiency in catalyzing photochemical H evolution from a molecular system of Ru(bpy)Cl-ascorbic acid (HA) under visible light irradiation (≥420 nm), providing a turnover number of 1570 and an initial turnover frequency of 335 h for H evolution based on the [MoS] catalyst.
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.
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