In this work, we demonstrated the practical use of Au@Cu2O core–shell and Au@Cu2Se yolk–shell
nanocrystals
as photocatalysts in photoelectrochemical (PEC) water splitting and
photocatalytic hydrogen (H2) production. The samples were
prepared by conducting a sequential ion-exchange reaction on a Au@Cu2O core–shell nanocrystal template. Au@Cu2O and Au@Cu2Se displayed enhanced charge separation as
the Au core and yolk can attract photoexcited electrons from the Cu2O and Cu2Se shells. The localized surface plasmon
resonance (LSPR) of Au, on the other hand, can facilitate additional
charge carrier generation for Cu2O and Cu2Se.
Finite-difference time-domain simulations were carried out to explore
the amplification of the localized electromagnetic field induced by
the LSPR of Au. The charge transfer dynamics and band alignment of
the samples were examined with time-resolved photoluminescence and
ultraviolet photoelectron spectroscopy. As a result of the improved
interfacial charge transfer, Au@Cu2O and Au@Cu2Se exhibited a substantially larger photocurrent of water reduction
and higher photocatalytic activity of H2 production than
the corresponding pure counterpart samples. Incident photon-to-current
efficiency measurements were conducted to evaluate the contribution
of the plasmonic effect of Au to the enhanced photoactivity. Relative
to Au@Cu2O, Au@Cu2Se was more suited for PEC
water splitting and photocatalytic H2 production by virtue
of the structural advantages of yolk–shell architectures. The
demonstrations from the present work may shed light on the rational
design of sophisticated metal–semiconductor yolk–shell
nanocrystals, especially those comprising metal selenides, for superior
photocatalytic applications.