Unraveling Interband Hot-Electron Transfer in Hydrogenated Au@Cu₂O/TiO₂ Heterostructure Nanocrystals for Enhanced Hydrogen Evolution.

We report the design and fabrication of a novel hydrogenated photoactive composite, H:(Au@Cu₂O/TiO₂). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) confirmed a well-defined core-shell architecture with a p-n heterojunction configuration. Optical and electronic band structures were systematically investigated. The localized surface plasmon resonance LSPR-induced inter-band electron transfer process from Au to Cu₂O shell was elucidated from the transient absorption spectra (TAS) and in situ X-ray absorption spectroscopy (XAS). A comprehensive charge-transfer mechanism was provided; the Z-scheme configuration facilitates charge transfer and separation for improved efficiency with Cu₂O shell and TiO₂ NPs to complete the redox cycle. The hydrogenated heterostructure exhibited an exceptional H₂ evolution rate of 9.3 mmol g⁻ ¹ h⁻ ¹ under AM 1.5 illumination while maintaining excellent stability. This enhancement is mainly attributed to direct injection of Au LSPR, a 3.9 times improvement with respect to H:(Cu₂O/TiO₂) of 2.4 mmol g⁻¹ h⁻¹ which was not reported before. Apparent quantum yield (AQY) measurements reached 2.5% at 650 nm and 0.8% at 800 nm, effectively extending the photocatalytic activity into the near-infrared region. These results highlight the robust H:(Au@Cu₂O/TiO₂) photocatalyst as a highly promising platform for photocatalytic hydrogen evolution with methanol as an efficient hole scavenger and broader photoconversion applications.