Thermodynamic and kinetic roles of H2 in structure evolution of urchin-like Co: A density functional theory study--颗粒学报PARTICUOLOGY

Wang, X., Liu, N., Zhang, Q., Liang, X., Chen, B., & Mei, D. (2020). Thermodynamic and kinetic roles of H2 in structure evolution of urchin-like Co: A density functional theory study. Particuology, 48, 2-12. https://doi.org/10.1016/j.partic.2018.08.007

Thermodynamic and kinetic roles of H₂ in structure evolution of urchin-like Co: A density functional theory study

Xiaolei Wang ^a, Ning Liu ^b *, Qinwei Zhang ^a, Xin Liang ^a, Biaohua Chen ^b, Donghai Mei ^c

a State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
b College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China
c Institute of Integrated Catalysis, Pacific Northwest National Laboratory, Richland, WA 99352, USA

10.1016/j.partic.2018.08.007

Volume 48, February 2020, Pages 2-12

Received 8 May 2018, Revised 17 July 2018, Accepted 7 August 2018, Available online 10 February 2019, Version of Record 27 January 2020.

E-mail: liuning@bjut.edu.cn

Highlights

• H₂ molecules affect the surface Gibbs free energies of Co nanocrystals.

• Phase diagram of stable H coverage on each Co surface constructed.

• Morphology of the Co nucleus predicted by the Wulff construction.

• Effect of H coverage on the diffusion rate of Co adatoms investigated.

• Thermodynamic and kinetic roles of H₂ investigated.

Abstract

Small gas molecules acting as good capping agents play important roles in controlling the morphologies and surface structures of metal nanocrystals. In the present work, the thermodynamic and kinetic roles of H₂ molecules in the morphology of Co nanocrystals were systematically studied by density functional theory (DFT). The Gibbs surface free energies of Co(100), Co(110), and Co(111) at different hydrogen surface coverages were determined by ab initio thermodynamics. The phase diagram of stable H coverage on each plane was obtained and morphology evolution of the Co nanocrystals with various surface hydrogen coverages was predicted by the Wulff construction. Addition of H₂ changes the facet stability, generating diverse morphological Co nuclei. The kinetic role of H₂ in adatom Co surface diffusion at different H coverages was investigated by DFT. The results suggest that surface H hinders Co surface diffusions, except for Co(100) at 0.56 monolayer coverage. The projected density of states gives deeper insight into the electronic structures of Co adatoms with addition of the surface H atoms, which affect its surface diffusion ability.

Graphical abstract

Keywords

Nanocrystal Co; Surface free energy; Surface diffusion; Density functional theory

文章导读