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 alpha-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.