Efficient utilization of solar energy is a high-priority target and the search for suitable materials as photocatalysts that not only can harvest the broad wavelength of solar light, from UV to near-infrared (NIR) region, but also can achieve high and efficient solar-to-hydrogen conversion is one of the most challenging missions. Herein, using Au/La Ti O (BP-Au/LTO) sensitized with black phosphorus (BP), a broadband solar response photocatalyst was designed and used as efficient photocatalyst for H production. The optimum H production rates of BP-Au/LTO were about 0.74 and 0.30 mmol g h at wavelengths longer than 420 nm and 780 nm, respectively. The broad absorption of BP and plasmonic Au contribute to the enhanced photocatalytic activity in the visible and NIR light regions. Time-resolved diffuse reflectance spectroscopy revealed efficient interfacial electron transfer from excited BP and Au to LTO which is in accordance with the observed high photoactivities.
Two-dimensional
layered black phosphorus (BP) with a tunable band
gap of 0.3–2.0 eV has received great interest in broad-spectrum-active
photocatalysis, but rapid charge recombination limits its potential
applications. Herein, we report that BP quantum dots (QDs) work as
active photosensitizer in a ternary heterostructure consisting of
BP QDs, Au nanorods (NRs), and CdS nanowires (NWs), which efficiently
photocatalytically generates H2 at full solar spectrum,
especially in the near-infrared (NIR) region. The superior performance
of the BP–Au–CdS heterostructure arises from the overall
photoabsorption contribution, the dual role (electron relay and plasmonic
electron donor) of Au NRs, as well as the appropriate band alignment
and strong coupling between the three components. Tracking the electron
and hole transfers via femtosecond transient absorption spectroscopy
shows a unidirectional electron flow from BP to Au and then to CdS,
which has been achieved by the high conduction band level of BP, the
well-harnessed work function match in BP–Au, and the well-established
Schottky barrier in Au–CdS heterojunction.
Visible
and near-infrared (NIR) light utilization is a high-priority
target for solar-to-chemical energy conversion. In this work, a promising
surface heterojunction-based plasmonic photocatalyst was developed
by integrating Au nanorods (NRs) with La2Ti2O7 nanosteps (Au-LTO NSP) for photocatalytic H2 evolution in visible and near-infrared (NIR) regions. At wavelengths
longer than 420 nm, Au-LTO NSP displayed H2 production
rate that was separately 2.4 and 4.7 times that of Au-LTO nanosheets
(NS) and Au–P25 composites, using methanol as the sacrificial
agent. At wavelengths longer than 780 nm, the enhancement was 2.3
and 5.8 times, respectively. The high apparent quantum efficiency
(AEQ) of 1.4% at 920 nm irradiation makes the Au-LTO NSP photocatalyst
especially efficient for the NIR light utilization. The broadband
photocatalytic activity of Au-LTO NSP was mainly caused by longitudinal
surface plasmon resonance of Au NRs, generating and injecting hot
electrons into LTO NSP. Substantial electrons transferred from Au
NRs to the (010) facets and then directionally migrated to the (012)
facets of LTO NSP, as consequence of the successive (010) and (012)
surface heterojunctions within a LTO NSP single particle. The unique
step structure of LTO retarded the recombination of the photoinduced
electrons and holes in Au NRs, showing the powerful role of the semiconductor
surface heterojunction in favoring the plasmon-induced interfacial
hot electron transfer.
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