Hydrogen, the smallest and lightest element, quickly penetrates various materials and alters their physical properties. Determining the precise location and quantity of hydrogen in the crystal lattice is crucial for understanding and controlling these hydrogen-induced changes in material behavior.
Now, scientists from Japan have focused on finding an easy way to locate it in nanofilms. The team used a combination of nuclear reaction analysis (NRA) and ion channeling to map the locations of hydrogen (H) and deuterium (D) in epitaxial titanium hydride nanofilms. The locations were determined by analyzing two-dimensional angular mappings of NRA yields.
The scientists aimed to overcome the challenge of detecting hydrogen atoms in materials, which is difficult with conventional methods like electron probes or X-rays due to their low sensitivity to tiny particles.
They combined nuclear reaction analysis (NRA) with ion channeling to create two-dimensional angular maps of hydrogen’s location in titanium hydride nanofilms to address this. This approach enables more precise detection of hydrogen and its distribution, which is crucial for tailoring the material’s properties.
The study’s lead author, Takahiro Ozawa, said, “We took a close look at a TiH1.47 nanofilm. Understanding nanofilms is useful as many hydrogen-related applications involve surface and subsurface reactions. We were able to locate both the hydrogen and deuterium atoms in the nanofilm precisely.”
The study found that all deuterium atoms (a hydrogen isotope) occupied tetrahedral positions in the titanium crystal structure. In contrast, 11% of the hydrogen atoms were at octahedral sites. The presence of both types of sites reduced the symmetry of the lattice, enhancing its stability.
The researchers noted that the deuterium atoms didn’t occupy octahedral sites due to nuclear quantum effects. This insight suggests that by controlling the ratio of hydrogen isotopes (e.g., hydrogen vs. deuterium), it could be possible to fine-tune the stability and properties of titanium hydride nanofilms for specific applications.
Senior author Katsuyuki Fukutani said, “Being able to differentiate between the two isotopes in the hydride revealed an opportunity for control. This will have important practical applications for producing particular hydrogen-induced phenomena.”
The improved understanding of titanium hydride nanofilms is expected to have significant implications for various applications, including hydrogen storage, solid electrolytes, and heterogeneous catalysis. These advancements are crucial as we work towards developing practical and safe green solutions for the future, particularly in the context of sustainable energy and environmental technologies.
Journal Reference:
- Ozawa, T., Sugisawa, Y., Komatsu, Y. et al. Isotope-dependent site occupation of hydrogen in epitaxial titanium hydride nanofilms. Nat Commun 15, 9558 (2024). DOI: 10.1038/s41467-024-53838-6
