Tailoring Defect-Rich Pt/Co3O4 by Facet Engineering for Efficient Selective Hydrogenation of Cinnamaldehyde

Abstract Improving the selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) remains a challenge due to the coexistence of C═O and C═C bonds in the CAL molecule. Herein, we synthesized a series of Pt/Co3O4 catalysts that utilized Co3O4 supports with dominant (220) or (311) crystal facets to anchor Pt nanoparticles (NPs) and engineer oxygen vacancies for surface microstructure modulation, thereby enhancing chemoselectivity toward the C═O bond. Theoretical calculations demonstrated a lower oxygen vacancy formation energy for Pt/Co3O4-220 than for Pt/Co3O4-311, revealing a higher propensity for oxygen defect formation on the (220) crystal facet. Combined with in situ Fourier transform infrared (FTIR), the results revealed that a high concentration of oxygen vacancies not only facilitates C═O adsorption but also promotes intermediate desorption, thereby avoiding deep hydrogenation of COL. As a result, the Pt/Co3O4-220-120 catalyst exhibited exceptional performance with near-quantitative CAL conversion (99.8%) within 6 h and remarkable chemoselectivity (94.1%) toward the C═O bond. This strategy demonstrates that defect site via crystal facet engineering control enables the rational design of efficient nanocatalysts for selective CAL hydrogenation.