Prominence of copper in AuCu alloy towards enhance surface plasmon resonance-driven water oxidation

Abstract

To fully harness the potential of surface plasmon resonance (SPR) in augmenting photocatalytic water oxidation, a comprehensive exploration of structure-activity relationship of metal nanoparticles is essential. This work presents a wrap-bake-peel (WBP) strategy designed to stabilize AuCu/TiO2 nanostructures while preserving SPR absorption and refining the metal-semiconductor interfaces. Through strategically incorporating trace Cu into Au (Cu/Au = 0.06), we achieved a 2.6-fold enhancement of SPR-induced oxygen evolution reaction (OER) performance compared to pristine Au/TiO2. This enhancement is due to the synergistic effect of SPR and a well-defined Schottky barrier, which improves plasmonic hot carrier charge separation, as verified by detailed spectroscopic analyses. The incorporation of copper plays a critical role, acting as an electron shuttle that facilitates the transfer of hot electrons from photoexcited gold to the AuCu NP surface, thereby reducing recombination. This process, driven by SPR-induced hot electrons from Au, also extends electron-phonon (τ0e-ph), interactions by 138 %, significantly prolonging hot carrier lifetimes. Mechanistic insights reveal that d-band onset potentials (Ed-AuCu∼-0.9 V/ Ed-Au∼-1.2 V) and increased hot hole d-band occupancy in AuCu further enhance the overall SPR-induced water oxidation performance. Simulated electron distributions and quantum confinement in AuCu vs. Au critically dictate SPR characteristics, enabling precise modulation of plasmonic responses. These findings underscore the crucial role of Cu in fine-tuning the properties of plasmonic photocatalysts, demonstrating a significant advancement in the rational design of efficient solar-to-fuel conversion systems.