Plasmon enhanced selective electronic pathways in TiO2 supported atomically ordered bimetallic Au-Cu alloys

- Greatest visible light photo-enhancement for acetaldehyde formation on Au3Cu4/TiO2.
- High selectivity due to CC cleavage inhibition by atomically ordered Au-Cu alloy.
- Cu-Au selective electronic transfer supplants Au-TiO2 interfacial interactions.
- LSPR in combination with XPS and DRIFTS ascertain selective electronic pathways.

Herein, we investigate the mechanisms involved in the selective oxidation of ethanol to acetaldehyde by localised surface plasmon resonance (LSPR) enhanced Au-Cu alloys. Temperature programmed oxidation results in tandem with quantitative in-situ DRIFTS of the surface species under different illumination conditions revealed that the cleaving of CC bonds at the Au-TiO2 interface were inhibited in the presence of Cu at temperatures <175 °C. HAADF-STEM and XPS analysis of the spent catalysts demonstrated that the suppression of CC cleavage was due to selective electron transfer between the atomically ordered Cu and Au arrays. Thus, the selectivity of Au-Cu/TiO2 towards the formation of acetaldehyde could be enhanced by over 800% at 100 °C under visible light illumination compared to standard thermal catalysis. Nonetheless, the selective electron charge transfer was disrupted at temperature >175 °C, lowering acetaldehyde selectivity. The work suggests that LSPR photo-enhancement is defined by the inherent electronic interactions within the bimetallic alloy and is facilitated by atomically ordering of the Au-Cu arrays. As such, in addition to performance enhancement, LSPR photo-enhancement can be used in combination with other characterisation techniques to ascertain the selective electronic pathways in bimetallic catalysts.

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