Effect of Ceria Support on the Structure of Ni Nanoparticles

Abstract

The effect of nanostructures of ceria associated with oxygen vacancies as well as Ti dopant on the structure of Ni was investigated by adopting model Ni/ceria systems consisting of Ni nanoparticles supported on well-ordered CeOx(111) (1.5 < x < 2) thin films with/without Ti dopant using scanning tunneling microscopy under ultrahigh vacuum conditions. The surface defects related with oxygen vacancies on the reduced ceria act as the nucleation sites for Ni, which causes the formation of Ni particles with a smaller size and a higher particle density compared to those on CeO2 at 300 K. Ni experiences a significant particle aggregation on pure ceria surfaces upon heating to higher temperatures, although slightly less Ni sintering was observed on the reduced ceria. Doping ceria with Ti element can help prevent the Ni sintering and stabilize the Ni particles on the surface upon heating, making it an attractive support for practical Ni catalysts with high stability.