Catalytic Activities of Low‐Coordinated Ce for Methane Conversion

Abstract

In heterogeneous catalysis, the catalytic activity of an active center strongly correlates with its coordination number. In this work, density functional theory calculations corrected by on‐site Coulomb interactions were conducted to investigate the catalytic performances of the CeO4‐terminated reconstructed CeO2(100) (CeO4‐t) and the Ca‐doped CeO4‐t surfaces. The undoped CeO4‐t surface contains single 4‐fold coordinated Ce (Ce4c) sites on its top surface layer, and the Ca‐doped CeO4‐t surface can expose even lower‐coordinated 3‐fold Ce (Ce3c) sites. We found that the empty 4f states of the single Ce3c sites on the Ca‐doped CeO4‐t surface have much lower energies than that of the single Ce4c sites on the undoped CeO4‐t surface, which can effectively boost the reduction of Ce4+ to Ce3+. We further studied the selective oxidation of CH4 to CH3OH on the two surfaces and found that the isolated nature combined with the strong electron‐reservoir character of the single Ce3c site makes it highly desirable for the selective activation of the first C−H bond of CH4, while the subsequent C−H bond cleavage step is less affected by such low‐coordinated Ce and the CH3OH formation becomes more facile on the Ca‐doped CeO4‐t surface, giving rise to the high activity and selectivity of the Ca‐doped CeO4‐t surface toward the selective oxidation of CH4 to CH3OH.

Shape-Controlled Pathways in the Hydrogen Production from Ethanol Steam Reforming over Ceria Nanoparticles

“…We further note that the catalytic activity of the clean and hydroxylated (100)-Mix surfaces has been considered in several recent studies. 53 , 54 …”

“…We point out that in this work, the most stable configuration of dissociated water and ethanol has not been sought, but rather how the presence of neighboring hydroxyl groups influences the nature and stability of adsorbed ethoxy species and their vibrational frequencies. We further note that the catalytic activity of the clean and hydroxylated (100)-Mix surfaces has been considered in several recent studies. , …”

“…We further note that the catalytic activity of the clean and hydroxylated (100)-Mix surfaces has been considered in several recent studies. 53,54 The adsorption energy of the dissociatively chemisorbed ethanol was calculated according to the following equation for the hydroxylated ceria surfaces:…”