Simultaneous Stabilization of Copper Species and Regulation of the Cu+/Cu0 Balance on SiO2 for Selective Ethanol Dehydrogenation

Abstract

Selective ethanol dehydrogenation is a promising route for acetaldehyde production; however, achieving stable copper catalysts on inert supports with a well-balanced Cu+/Cu0 ratio remains challenging. Herein, we report a urea-assisted strategy to simultaneously stabilize copper species and regulate the Cu+/Cu0 balance on a silica support. The gradual release of ammonia promotes the formation of interfacial Cu–O–Si linkages and basic copper nitrate species, which serve as precursors for Cu+ and Cu0, respectively. The resulting catalyst exhibits highly dispersed copper species with a balanced Cu+/Cu0 distribution, delivering high activity, >95% acetaldehyde selectivity, and stable performance in ethanol dehydrogenation. Mechanistic studies reveal that Cu+ sites facilitate ethanol activation, while Cu0 sites promote C–H bond cleavage. However, excessive Cu+ species lead to the formation of strongly adsorbed enolic intermediates, which trigger C–C coupling and byproduct formation. This work highlights the importance of Cu+/Cu0 synergy and provides a general strategy for designing stable and selective copper-based catalysts on inert supports.