Ceria crystal facet impact for methane C–H activation in Pd/CeO2 catalysts

Abstract

The exposed facets of ceria crystals have a profound effect on the reactivity of ceria-supported catalysts owing to the intricate metal–support interactions. In this work, ceria nanorods, nanocubes, and polyhedra, with corresponding exposed (110)/(100), (100), and (111) terminations, were hydrothermally synthesized to support Pd species, with the aim of investigating the in-depth impacts of ceria crystal facets for methane combustion over ceria-supported palladium catalysts. The nanorod sample delivered the highest methane conversion (T₅₀ = 277 °C, GHSV = 200 000 mL h⁻¹ g_cat⁻¹) and greater reaction rate (9.59 × 10⁻⁴ mol_CH4 h⁻¹ g_cat⁻¹), 1.23 times that of nanocubes and 3.14 times that of polyhedra. Further characterizations revealed that on the (110)/(100) surface planes, PdO_x exhibited stronger interactions with CeO₂. This led to enhanced formation of Pd⁴⁺ and higher reducibility of PdO_x species, thus promoting methane activation. This work would supply experimental insights into the relationship between exposed facets and reactivity, as well as guidance for rational catalyst design.