Spectroscopic evidence for origins of size and support effects on selectivity of Cu nanoparticle dehydrogenation catalystsElectronic supplementary information (ESI) available: Catalyst synthesis and characterization procedures; TEM and cluster size distributions; LCs for TPR-XANES; XRD patterns; selectivity and rate measurements. See DOI: 10.1039/c6cc08305f

Selective dehydrogenation catalysts that produce acetaldehyde from bio-derived ethanol can increase the efficiency of subsequent processes such as C-C coupling over metal oxides to produce 1-butanol or 1,3-butadiene or oxidation to acetic acid. Here, we use in situ X-ray absorption spectroscopy and steady state kinetics experiments to identify Cu δ + at the perimeter of supported Cu clusters as the active site for esterification and Cu 0 surface sites as sites for dehydrogenation. Correlation of dehydrogenation and esterification selectivities to in situ measures of Cu oxidation states show that this relationship holds for Cu clusters over a wide-range of diameters (2-35 nm) and catalyst supports and reveals that dehydrogenation selectivities may be controlled by manipulating either. Spectroscopic and selectivity measurements identify Cu δ + atoms at the cluster-support interface as active sites for esterification of ethanol and acetaldehyde.