Unraveling Interband Hot‐Electron Transfer in Hydrogenated Au@Cu ₂ O/TiO ₂ Heterostructure Nanocrystals for Enhanced Hydrogen Evolution

ABSTRACT We report the design and fabrication of a novel hydrogenated photoactive composite, H:(Au@Cu ₂ O/TiO ₂ ). 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 Cu ₂ O 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 Cu ₂ O shell and TiO ₂ NPs to complete the redox cycle. The hydrogenated heterostructure exhibited an exceptional H ₂ 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:(Cu ₂ O/TiO ₂ ) 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@Cu ₂ O/TiO ₂ ) photocatalyst as a highly promising platform for photocatalytic hydrogen evolution with methanol as an efficient hole scavenger and broader photoconversion applications.