Morphology-Dependent Cu ⁺ Stabilization and Metal–Support Interactions Govern Catalytic Transfer Hydrogenation of Furfural over Cu/CeO ₂

A series of Cu/CeO₂ catalysts were prepared using CeO₂ supports with distinct morphologies (rods, cubes, and polyhedra) to investigate their effect on the catalytic transfer hydrogenation (CTH) of furfural (FAL) to furfuryl alcohol (FOL). Morphology-dependent variations led to significant differences in the oxygen vacancy (O_V) concentration, metal-support interaction (MSI), Cu oxidation states, and surface acidity. Among the catalysts, Cu/CeO₂-P (polyhedron) exhibited the highest specific surface area, favorable exposure of Cu (111) and (200) facets, the highest O_V density, and abundant Cu⁺ species stabilized via a Cu⁺-O_V-Ce³⁺ interfacial structure. Strong MSI in this system facilitated electronic interactions and suppressed over-reduction of Cu⁺ to Cu⁰. Additionally, Cu/CeO₂-P possessed the highest total acidity, including abundant weak and moderate acid sites, which synergistically enhanced the adsorption of carbonyl groups and β-H activation in isopropanol. These combined effects promoted efficient hydrogen transfer and selective C═O reduction. As a result, Cu/CeO₂-P achieved the best catalytic performance, with 97.6% FAL conversion, 98.5% FOL selectivity, and 33.2 h^-1 turnover frequency at 150 °C for 8 h. This study demonstrates how CeO₂ morphology governs the electronic and catalytic properties of Cu/CeO₂ catalysts, offering insights into the rational design of efficient, Cu-based catalysts for biomass valorization.