Single-atom Pd boosted Cu catalysts for ethanol dehydrogenation

Abstract

Ethanol dehydrogenation is a vital elementary step in ethanol upgrading, for which Cu-based alloy catalysts are the most promising candidates. Nevertheless, elucidating the underlying reasons for the synergistic effect between alloying components and host metals remains challenging due to the intrinsic structural complexity and dynamic evolution of alloy catalysts under operational conditions. Herein, single-atom Pd modified Cu-MFI catalysts with well-defined structures were designed for ethanol dehydrogenation to acetaldehyde and hydrogen. Comprehensive characterizations using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed that Pd atoms are isolated by surrounding Cu atoms with a coordination number of 9–10, forming −0.36e charged single-atom sites and being uniformly dispersed on the surface of Cu catalysts. The newly generated Pd^δ− and Cu^δ+ sites synergistically reduced the activation energy barrier for C–H bond cleavage in ethanol. These sites simultaneously enhanced hydrogen adsorption and H–H bond coupling, leading to improved ethanol conversion and acetaldehyde productivity over Pd/Cu-MFI catalysts.