Abstract
Phase transitions of metals in hydrogen (H) environments are critically import- ant for applications in energy storage, catalysis, and sensing. Nanostructured metallic particles can lead to faster charging and discharging kinetics, increased lifespan, and enhanced catalytic activities. However, establishing a direct causal link between nanoparticle structure and function remains challenging. In this work, we establish a computational framework to explore the atomic config- uration of a metal-hydrogen system when in equilibrium with a H environ- ment. This approach combines Diffusive Molecular Dynamics with an itera- tion strategy, aiming to minimize the system’s free energy and ensure uniform chemical potential across the system that matches that of the H environment. Applying this framework, we investigate H chemical potential-composition isotherms during the hydrogenation and dehydrogenation of palladium nano- particles, ranging in size from 3.9 nm to 15.6 nm and featuring various shapes including cube, rhombic dodecahedron, octahedron, and sphere. Our findings reveal an abrupt phase transformation in all examined particles during both H loading and unloading processes, accompanied by a distinct hysteresis gap between absorption and desorption chemical potentials. Notably, as particle size increases, absorption chemical potential rises while desorption chemical potential declines, consequently widening the hysteresis gap across all shapes. Regarding shape effects, we observe that, at a given size, cubic particles exhibit the lowest absorption chemical potentials during H loading, whereas octahedral particles demonstrate the highest. Moreover, octahedral particles also exhibit the highest desorption chemical potentials during H unloading. These size and shape effects are elucidated by statistics of atomic volumetric strains result- ing from specific facet orientations and inhomogeneous H distributions. Prior to phase transformation in absorption, a H-rich surface shell induces lattice expansion in the H-poor core, while before phase transformation in desorption, surface stress promotes lattice compression in the H-rich core. The magnitude of the volumetric strains correlates well with the size and shape dependence, underlining their pivotal role in the observed phenomena.
Document Type
Article
Publication Date
11-2024
Digital Object Identifier (DOI)
https://doi.org/10.1088/1361-651X/ad89e3
Funding Information
The material is based upon work supported by NASA Kentucky under NASA Award No: 80NSSC20M0047. X S gratefully acknowledges the support from the University of Kentucky through the faculty startup fund and the e-RPA seed grant program. We would thank the University of Kentucky Center for Computational Sciences and Information Technology Services Research Computing for their support and use of the Lipscomb Compute Cluster and associated research computing resources. The suggestions of the three anonymous reviewers have helped to improve the quality and scope of this work.
Repository Citation
Sun, Xingsheng and Jin, Rong, "Size and shape dependence of hydrogen-induced phase transformation and sorption hysteresis in palladium nanoparticles" (2024). Chemical and Materials Engineering Faculty Publications. 88.
https://uknowledge.uky.edu/cme_facpub/88
Included in
Chemical Engineering Commons, Materials Science and Engineering Commons, Numerical Analysis and Scientific Computing Commons
Notes/Citation Information
© 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.