(2024/03/29)

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Storing Electrons from Hydrogen for Clean Chemical Reactions
Researchers engineer a compound that can store electrons from hydrogen at room
temperature and release them in useful chemical reactions
Fukuoka, Japan—Researchers from Kyushu University have developed a hydrogen energy
carrier to address some of the biggest hurdles in the path towards a sustainable hydrogeneconomy. As explained in a paper published in JACS Au, this novel compound can efficiently“store electrons” from hydrogen in a solid state to use in chemical reactions later.
Hydrogen is a promising source of clean energy with a lot of untapped potential applications inindustry and everyday life. Unlike conventional fuels, hydrogen can be used to generate
electricity without producing greenhouse gases. It can also be used in various chemical
reactions such as hydrogenation, that is, as a source of hydride ion or hydrogen atom electrons.
However, storing and transporting hydrogen in either gaseous or liquid states is extremely
challenging, requiring expensive equipment and cooling systems.
Professor Seiji Ogo from Kyushu University’s WPI-International Institute for Carbon-Neutral
Energy (WPI-I2CNER) has been developing innovative solutions to these problems. In their mostrecent study, Ogo and his colleague from Kindai University took inspiration from nature todevelop an iridium-based compound with peculiar and remarkably useful properties.
“We have been actively exploring hydrogen energy carriers that can be easily synthesized andused as-is. These compounds are based on the hydrogenase enzyme found in nature, which
can catalyze hydrogen into protons and electrons at room temperature,” explains Ogo. “A coreidea of our approach that led to a breakthrough was to view hydrogen not as a source ofnegatively charged hydride ion or hydrogen atom, but as electrons.”
After carefully examining many combinations of metal ions and organic ligands, the researchteam crafted an iridium-based compound which, when exposed to hydrogen incorporates it into
the metal center after losing an iodide ion. In this way, the proposed compound can effectively
extract and store electrons from hydrogen.
These changes are readily reversible under the right conditions, and the stored electrons canbe easily extracted and used in chemical reactions to synthesize valuable molecules. In thisstudy, the researchers focused on using the electrons stored in the compound to catalyze
cyclopropanation reactions.
Cyclopropanes are molecules with a three-membered carbon ring structure and represent
important structural units in various pharmaceutical drugs and organic compounds. However,conventional cyclopropanations have produced large amounts of waste metals as byproducts.
The proposed hydrogen energy carrier circumvents this issue entirely.
“The cyclopropanation reactions performed in our study use hydrogen rather than metals as
the reductant and thus produce no metal waste. This is a major advantage of the proposedcompound over established techniques,” remarks Ogo.
Notably, this study also marks the first time that a reaction between hydrogen and alkenes—hydrocarbons containing a carbon double bond—produces cyclopropanes rather than the much
simpler alkanes.
After extensive testing, the team found that the proposed energy carrier can capture electronsfrom hydrogen and store them for over three months in solid state at room temperature.
In future work, Ogo and colleagues plan to focus on developing a similar energy carrier usingiron-group elements, which are cheaper and more abundant than iridium. By promoting
industry-academia collaborations, their next efforts will aim to develop scalable solutions forpractical problems surrounding upcoming hydrogen economies.
“We sincerely believe that the present achievement will contribute to the realization of a carbonneutral society,” concludes Ogo.
###For more information about this research, see "Cyclopropanation using Electrons Derived fromHydrogen—Reaction of Alkenes and Hydrogen without Hydrogenation”, Seiji Ogo, Takeshi
Yatabe, Keishi Miyazawa, Yunosuke Hashimoto, Chiaki Takahashi, Hidetaka Nakai, andYoshihito Shiota, JACS Au, DOI: https://doi.org/10.1021/jacsau.4c00098
About Kyushu University
Kyushu University is one of Japan's leading research-oriented institutes of higher education
since its founding in 1911. Home to around 19,000 students and 8,000 faculty and staff,
Kyushu U's world-class research centers cover a wide range of study areas and researchfields, from the humanities and arts to engineering and medical sciences. Its multiple
campuses—including one of the largest in Japan—are located around Fukuoka City, a coastal
metropolis on the southwestern Japanese island of Kyushu that is frequently ranked among
the world's most livable cities and historically known as Japan's gateway to Asia. Through its
Vision 2030, Kyushu U will 'Drive Social Change with Integrative Knowledge.' Its synergistic
application of knowledge will encompass all of academia and solve issues in society while
innovating new systems for a better future.
About International Institute for Carbon-Neutral Energy Research (WPI-I²CNER)
Kyushu University
Contribute to the creation of a sustainable and environmentally friendly society I²CNER's
mission is to contribute to the creation of a sustainable and environmentally-friendly society byadvancing low-carbon emission and cost-effective energy systems, and improvement of energy
efficiency. Through its mission-driven basic research, I²CNER has been developing andconducting research on scientific technologies to drastically reduce CO2 emissions.
https://i2cner.kyushu-u.ac.jp/en/
About the World Premier International Research Center Initiative (WPI)
The WPI program was launched in 2007 by Japan's Ministry of Education, Culture, Sports,
Science and Technology (MEXT) to foster globally visible research centers boasting the highest
standards and outstanding research environments. Numbering more than a dozen andoperating at institutions throughout the country, these centers are given a high degree ofautonomy, allowing them to engage in innovative modes of management and research. The
program is administered by the Japan Society for the Promotion of Science (JSPS).
See the latest research news from the centers at the WPI News Portal:
https://www.eurekalert.org/newsportal/WPI/home
Main WPI program site
https://www.jsps.go.jp/english/e-toplevel/

(a) Reaction diagram of a newly conceived
hydrogen energy carrier
Use of electrons(b) Metal waste-free reaction
Metal Reducing
AgentsCyclopropanation reaction

R1 R2
CH2I2 +

R1 R 2R1 R2

conventional+ H++ Metal waste

cyclopropane

R1 R22+

NN

N

N+

NN
N

N

NN
I

From hydrogen atroom temperature
Extract electrons

OHNIrIINN
1Electron Storage

IH2

Extraction ofelectrons

No metalwaste(c) Reactions other than hydrogenation withalkenes and hydrogenH2N

conventional

R 1 R2alkanehydrogenation
reaction

R 1 R2
olefine2I– + H+R1 R2
cyclopropane

NN

IrIIO2Can be stored formore than 3 months

H2
this study

When you need it.
Always available
electronically

IrI

IrI

olefineH2
this study

R 1 R2
cyclopropane

Cyclopropanation
reactionFig. 1. Reversible extraction and storage of electrons from hydrogen to catalyze
cyclopropanation reactions. The proposed iridium-based compound can effectively store“electrons” from hydrogen and hold them in solid state at room temperature formonths. These stored electrons can then be released to catalyze cyclopropanation
reactions that do not produce metal waste.

[Contact]
Seiji Ogo, Professor
WPI-International Institute for Carbon-Neutral Energy, Kyushu University
E-mail: ogo.seiji.872@m.kyushu-u.ac.jp