Revealing the Crystal Facet Effect of Ceria in Pd/CeO2 Catalysts toward the Selective Oxidation of Benzyl Alcohol

Ceria is an excellent catalyst or support for various oxidation reactions due to its abundant oxygen vacancies and strong metal–support interactions. In this study, ceria nanocrystals were hydrothermally prepared with different morphologies (nanorods, nanocubes, and nano-octahedra) and corresponding exposed crystal facets [(110), (100), and (111)]. The Pd/CeO2 catalysts were synthesized through an impregnation method by applying these ceria nanocrystals as supports. Selective oxidation of benzyl alcohol, involving multiple catalytic steps, was employed as a model reaction to explore the crystal facet effect of ceria on the catalytic activity of various Pd/CeO2 catalysts. The Pd/CeO2 nanorod catalyst delivers superior performance in each individual step, resulting in an improved overall catalytic activity. Specifically, the highest oxygen vacancy concentration and the optimum metal–support synergy observed on the CeO2 (110) surface are feasible to dissociate the benzyl alcohol adsorbent, eliminate α-H, and activate O2. As a consequence, the Pd/CeO2-nanorod catalysts deliver a much higher benzyl alcohol conversion (74%) than Pd/CeO2-nano-octahedra (35%) and Pd/CeO2-nanocubes (28%). This work provides in-depth insight into the crystal facet–performance relationship of CeO2 in the selective oxidation of benzyl alcohol and sheds light on the catalyst support design strategy for other multistep reactions.