Tokyo Institute of Technology scientists have reported hydrogen stored in hydrogen boride sheets can be efficiently released electrochemically. Through a series of experiments, they demonstrated that dispersing these sheets in an organic solvent and applying a small voltage is enough to release all the stored hydrogen efficiently. The results suggest hydrogen boride sheets could soon become a safe and convenient way to store and transport hydrogen, which is a cleaner and more sustainable fuel.
Scientists worldwide are looking for cleaner alternatives to fossil fuels, and many believe hydrogen is our best bet. As an environmentally friendly energy resource when combusted or energizing a fuel cell, hydrogen as two atom dihydrogen (H2) can be used in vehicles and electric power plants.
Hydrogen release from hydrogen boride sheets explained graphically. Image Credit: Tokyo Institute of Technology. This image is too large and complex to reduce and show on a web post. The full size image can be seen at the press release page. It is also noteworthy that the study paper is Not behind a paywall at posting.
Meanwhile, storing and transporting H2 safely and efficiently remains a challenge. Compressed gaseous hydrogen poses quite significant risks of explosion and leakage, whereas liquid hydrogen must be maintained at extremely low temperatures, which is very costly.
This raised the question, what if we could store hydrogen directly in the molecular composition of other liquid or solid materials?
Storing hydrogen in HB sheets is not an entirely new concept, and many aspects of their potential applications as hydrogen carriers have already been studied.
However, getting the hydrogen out of the sheets is the tricky part. Heating at high temperatures or strong ultraviolet (UV) illumination is required to release H2 from HB sheets. But both approaches have inherent disadvantages, such as high energy consumption or incomplete H2 release.
So, the team started research into a potential alternative: electrochemical release.
In consideration of the mechanism of UV-induced H2 release from HB sheets, the team speculated that electron injection from a cathode electrode into HB nanosheets by an electric power supply could be a superior way to release H2 compared to UV irradiation or heating.
Based on this theory, the researchers dispersed HB sheets into acetonitrile – an organic solvent – and applied a controlled voltage to the dispersion. The experiments revealed that nearly all of the electrons injected into the electrochemical system were used to convert H+ ions from the HB sheets into H2 molecules.
Notably, the Faradaic efficiency of this process, which measures how much electrical energy is converted into chemical energy, was over 90%.
The team also conducted isotope tracing experiments to confirm that the electrochemically released H2 originated from the HB sheets and not through some other chemical reaction.
Moreover, they also employed scanning electron microscopy and X-ray photoelectron spectroscopy to characterize the sheets before and after H2 release, yielding further insights into the underlying mechanisms of the process.
These findings contribute to the development of safe and lightweight hydrogen carriers with low energy consumption.
Although the team studied the dispersed form of the HB sheets in the published paper, the current findings are applicable to film or bulk-based HB sheet systems for H2 release.
Additionally, the team will investigate the rechargeability of HB sheets after dehydrogenation in a future study.
The press release closes with, “With any luck, this line of research will help pave the way to cleaner energy sources and more sustainable societies!”
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This looks to be quite the breakthrough! There remains quite a list of questions, but the major ones about process and handling suggest this is a very promising start.
On the other hand, the weight to energy potential is the typical low of hydrogen. H2 is only two of the smallest atoms in the universe. The energy potential is always going to be small. The potential of multiple carbon atoms with a bunch of H2 wrapped around them common to organic matter and petroleum molecules such as designed and trialed by nature over hundreds of millions of years is way beyond where H2 can ever go.
Hydrogen does likely have a role in quite large niches. But it’s not clear that this tech would cut the risk of in-home storage to acceptable levels.
Let’s hope so though.
By Brian Westenhaus via New Energy and Fuel
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