Hydrogen's Quantum Tunnelling: Unlocking New Frontiers in Energy Storage
Hydrogen, the lightest element, has long been a key player in various physical, chemical, and biological processes. Its ability to tunnel through materials is particularly intriguing, but controlling this phenomenon has been a challenging task. Researchers from the University of Tokyo have recently made a groundbreaking discovery that could revolutionize hydrogen storage and transport.
Unveiling the Role of Crystal Symmetry
In a fascinating study, the team led by Dr. Katsuyuki Fukutani found that the degree of symmetry in a material's crystal structure significantly influences hydrogen's quantum tunnelling behavior. This finding opens up exciting possibilities for tailoring hydrogen transport, potentially leading to safer and more efficient storage methods.
Dr. Fukutani explains, "We observed that hydrogen exhibits pronounced quantum tunnelling in highly symmetric crystal environments. Conversely, when symmetry is reduced, tunnelling is strongly suppressed. This discovery establishes crystal symmetry as a fundamental principle for controlling hydrogen's quantum behavior, offering new avenues for customizing hydrogen transport."
A Model Hydrogen-Storage Material
The researchers focused on vanadium, a model hydrogen-storage material, to study hydrogen atoms' movement at low temperatures. They employed two advanced techniques: nuclear reaction analysis and electrical resistance measurements. These methods revealed that hydrogen atoms migrate through vanadium's crystal lattice, hopping between interstitial spaces.
At low hydrogen concentrations, the α-phase vanadium exhibits high symmetry, allowing hydrogen atoms to tunnel easily between neighboring lattice sites. However, at higher concentrations, the crystal lattice distorts, forming the β-phase. In this phase, hydrogen atoms face an energy barrier of 148 meV to tunnel to neighboring sites.
Quantum Tunnelling vs. Classical Thermal Activation
The team's electrical resistance measurements enabled them to calculate hydrogen's diffusion coefficient across various temperatures. By interpreting these results with quantum-mechanical calculations, they uncovered the relationship between crystal symmetry and hydrogen's motion. In the α-phase, hydrogen's ground states are delocalized due to tunnelling, while in the β-phase, uniaxial strain localizes hydrogen atoms around specific sites.
Dr. Fukutani notes, "Hydrogen's light nature makes its pronounced quantum behavior expected. However, observing quantum tunnelling directly in materials has been challenging. Our research aimed to clarify hydrogen's behavior in the quantum regime and identify the factors controlling its tunnelling."
Controlling Hydrogen Permeation and Storage
The study's findings suggest that tuning quantum tunnelling through crystal symmetry, such as applying external strain, can control hydrogen transport. This capability has far-reaching implications for hydrogen permeation, storage, and even catalytic reactions.
Looking ahead, the Tokyo researchers plan to expand their work to various hydrogen storage media, including metal alloys and oxide materials. Dr. Fukutani envisions, "We aim to establish a universal framework describing how local atomic structure and crystal symmetry govern hydrogen's quantum behavior."
This groundbreaking research, published in Nature Communications, marks a significant step forward in our understanding of hydrogen's quantum tunnelling and its potential applications in energy storage.
