Highly Efficient and Selective Hydrogenation of Cinnamaldehyde over Pt Nanoparticles and Single Atoms on Co ₂ AlO ₄ under Mild Conditions

In this study, a series of Pt/Co₂AlO₄ catalysts with varying Pt loadings (0.29 wt %, 0.91 wt %, and 2.73 wt %) were prepared via the wet impregnation method and evaluated for the selective hydrogenation of cinnamaldehyde. Among them, the 2.73 wt % Pt/Co₂AlO₄ catalyst exhibited the highest activity and selectivity. Under the reaction conditions of 60 °C, 2.0 MPa H₂, and 2 h, it achieved a cinnamaldehyde (CAL) conversion of 95.7% and a selectivity to cinnamyl alcohol (COL) of 82.8%. Moreover, the catalyst retained its performance over five consecutive recycling tests, demonstrating excellent stability. Based on comprehensive characterization, the superior catalytic behavior of the 2.73 wt % Pt/Co₂AlO₄ catalyst can be attributed to the following factors: (1) High dispersion of Pt species, with an average particle size of 1.25 ± 0.43 nm; (2) XPS analysis revealed distinct shifts in the binding energies of Co and Pt species, indicating electron transfer from Co to Pt. With increasing Pt loading, the binding energy of Pt further decreased, suggesting enhanced electron density; (3) H₂-TPD and H₂-TPR results confirmed strong hydrogen adsorption and activation capabilities for this catalyst. Collectively, these features contribute to the outstanding activity, high COL selectivity, and stable recyclability of the 2.73 wt % Pt/Co₂AlO₄ catalyst in the selective hydrogenation of cinnamaldehyde.