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-C bonds at the Au-TiO2 interface were inhibited in the presence of Cu at temperatures <175 degrees C. HAADF-STEM and XPS analysis of the spent catalysts demonstrated that the suppression of C-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 degrees C under visible light illumination compared to standard thermal catalysis. Nonetheless, the selective electron charge transfer was disrupted at temperature >175 degrees 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. (C) 2017 Elsevier Inc. All rights reserved.