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

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 C[sbnd]C 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 C[sbnd]C 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.