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.

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