Hydrogen spillover enhances the selective hydrogenation of α,β-unsaturated aldehydes on the Cu–O–Ce interface

Abstract

The industrially important selective hydrogenation of α,β-unsaturated aldehydes to allyl alcohol is still challenging to realize using heterogenous hydrogenation catalysts. Supported Cu catalysts have shown moderate selectivity, yet low activity for the reaction, due to the electronic structure of Cu. By anchoring atomically dispersed Pd atoms onto the exposed Cu surface of Cu@CeO2, we report in this work that hydrogen spillover activates the inert metal-oxide interfaces of Cu@CeO2 into highly effective and selective catalytic sites for hydrogenation under mild reaction conditions. The as-prepared catalysts exhibit much higher catalytic activity in the selective hydrogenation of acrolein than Cu@CeO2. Comprehensive studies reveal that atomically dispersed Pd species are critical for the activation and homolytic splitting of H2. The activated H atoms easily spill to the Cu–O–Ce interfaces as Cu–Hδ– and interfacial Ce–O–Hδ+ species, making them the active sites for hydrogenation of polar C=O bonds. Moreover, the weak adsorption of allyl alcohol on the Pd and Cu–O–Ce interfacial sites prevents deep hydrogenation, leading to selective hydrogenation of several α,β-unsaturated aldehydes. Overall, we demonstrate here a synergic effect between single atom alloy and the support for activation of an inert metal-oxide interface into selective catalytic sites.