Opposite Face Sensitivity of CeO2 in Hydrogenation and Oxidation Catalysis

The determination of structure–performance relationships of ceria in heterogeneous reactions is enabled by the control of the crystal shape and morphology. Whereas the (100) surface, predominantly exposed in nanocubes, is optimal for CO oxidation, the (111) surface, prevalent in conventional polyhedral CeO2 particles, dominates in C2H2 hydrogenation. This result is attributed to the different oxygen vacancy chemistry on these facets. In contrast to oxidations, hydrogenations on CeO2 are favored over low‐vacancy surfaces owing to the key role of oxygen on the stabilization of reactive intermediates. The catalytic behavior after ageing at high temperature confirms the inverse face sensitivity of the two reaction families. Shape and face matter: The design of ceria catalysts for oxidation and hydrogenation reactions is governed by opposite criteria. Whereas oxygen vacancies, maximized on (100) nanocubes, promote oxidation, hydrogenation is favored by their minimization, requiring (111) face‐enclosed polyhedral particles.