Researchers from the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, led by Professor Haimei Zheng, have uncovered new insights into how the shape of nanocrystals influences the pathways through which they transform between different phases. This research, published in the journal Nature Materials, has significant implications for the energy sector, particularly in the development of materials for energy storage technologies.
The team of researchers, including Daewon Lee, Sam Oaks-Leaf, Hyeonjong Ma, Jianlong He, Zhiqi Wang, Yifeng Shi, Eonhyoung Ahn, Karen C. Bustillo, Chengyu Song, Stephanie M. Ribet, Rohan Dhall, Colin Ophus, Mark Asta, Jiwoong Yang, Younan Xia, David T. Limmer, and Haimei Zheng, focused on palladium hydride (PdHx) nanocrystals. These nanocrystals are an ideal model system for studying phase transformations induced by the absorption of hydrogen, a process relevant to various energy storage technologies.
The researchers used advanced imaging techniques to directly observe the hydrogenation process in palladium nanocrystals of two different shapes: nanocubes and hexagonal nanoplates. They found that both shapes followed a similar sequence of events during phase transformation, including the formation of an initially curved nucleus, interface flattening, and reverse-stage nucleation. However, the specific crystallographic alignments of the evolving interfaces between the different phases of PdHx were dependent on the geometry of the nanocrystal.
In nanocubes, the interfaces aligned along the {100} crystallographic planes, conforming to the expected elastic energy ordering and maintaining local mechanical equilibrium. In contrast, nanoplates exhibited interfaces aligned along both {110} and {211} planes. Theoretical simulations conducted by the researchers showed that the geometry of the nanocrystal determines the accessibility of alternative phase transformation pathways, especially when the system is driven far from equilibrium during hydrogenation.
The findings of this research identify the shape of nanocrystals as a fundamental parameter that can be used to direct phase transformation pathways. This understanding offers new design principles for accessing atypical configurations and improving the properties of materials used in intercalation-based devices, such as batteries and fuel cells. By tailoring the geometry of nanocrystals, researchers can potentially enhance the performance and efficiency of energy storage technologies, contributing to the development of more sustainable and reliable energy systems.
The research was published in Nature Materials, a leading journal in the field of materials science. The insights gained from this study not only advance our fundamental understanding of phase transformations in nanocrystals but also provide practical applications for the energy sector, paving the way for the development of next-generation energy storage technologies.
This article is based on research available at arXiv.