Theoretical Studies on the Stability and Reactivity of the Metal-Doped CeO2(100) Surface: Toward H2 Dissociation and Oxygen Vacancy Formation.

Surface doping is a common method to improve the performance of nanostructured materials. Different dopants will affect the structure and catalytic reactivity of the support. For a comprehensive understanding of the doping effects of metals doped into CeO2, we conducted density functional theory (DFT) studies on the stabilities and geometry structures of transition-metal atoms (M = Fe, Co, Ni, Cu; Ru, Rh, Pd, Ag; Os, Ir, Pt, Au) doped into CeO2(111), (110), and (100) surfaces. Moreover, the reactivity for H2 dissociation and oxygen vacancy formation are systematically investigated on M-doped CeO2(100) surfaces. The greater the binding energies of doped M atoms on the CeO2 surface, the more difficult the formation of oxygen vacancies. The doped Co and Ir atoms do not directly participate in H2 activation but serve as a promoter to make the H-H bond to break easily. The Cu, Ru, Pd, Ag, Pt, and Au atoms could act as the catalytically active center for H2 dissociation and greatly reduce the activation energy barrier. Besides, it is easier to generate H2O (WM) and a surface oxygen vacancy from the intermediate H2M/H4M than from H3M/H5M, which is related to the acid-base interaction between HCe/M* and HO* in H2M/H4M. This work could provide theoretical insights into the atomic structure characteristics of the transition-metal-doped CeO2(100) surface and give ideas for the design of hydrogenation catalysts.