EFFECT OF WATER ON Ni AND Co DIFFUSION ON CeO2(111)

Author

Nusrat Jahan Rifat, Louisiana State University and Agricultural and Mechanical CollegeFollow

Semester of Graduation

Summer 2025

Degree

Master of Science in Chemical Engineering (MSChE)

Department

Chemical Engineering

Document Type

Thesis

Abstract

Nanoparticles of transition metals such as Co and Ni supported on ceria (CeO₂) are widely used to catalyze many technologically important reactions. The detailed nature of these metal nanoparticles and the factors affecting their interaction with ceria directly affect their catalytic performance. For unassisted diffusion, Ni₁ and Co₁ show sizeable barriers on clean CeO₂(111) at low metal coverage and RT, 1.3 eV and 1.1 eV, respectively. Theoretically predicted Co and Ni nanoparticles are found to be notably less flat than what is observed in STM line profiles. Additionally, particle density from STM suggests a VW growth mode that requires a finite diffusion length. Water, which is ubiquitous and may be present even in UHV apparatus, can affect metal-ceria interaction, including particle sintering. Based on this hypothesis, we performed computational modeling based on DFT calculations to investigate and propose a water-enhanced diffusion mechanism. Our results indicate that the interaction of water with Co and Ni can enhance the diffusion of these metals on ceria surface. This interaction creates hydroxylated Co and Ni adatoms, Co₁-OH and Ni₁-OH, that diffuse more rapidly than corresponding adatoms with barriers of 0.99 eV and 0.65 eV, respectively. Hydroxylated metal atoms are furthermore proposed to enable a cluster growth mechanism.

Date

7-9-2025

Recommended Citation

Rifat, Nusrat Jahan, "EFFECT OF WATER ON Ni AND Co DIFFUSION ON CeO2(111)" (2025). LSU Master's Theses. 6183.
https://repository.lsu.edu/gradschool_theses/6183

Committee Chair

Xu, Ye