PROFESSOR YURY GOGOTSI
Solving complex
chemical problems
Professor Yury Gogotsi is studying
ionic liquids in confined environments
with the hope that it will have important
implications to electrical energy-storage. Here he
describes how collaboration is furthering the project
Why is it important to understand more
about ionic liquids?
Ionic liquids are just molten salts. This
means that in the liquid state they
dissociate into ions that can be moved
when an electric field is applied, giving to
those liquids ionic conductivity, as it is
with salt in water. While most salts, such
as rock salt, will melt and become liquid
at high temperatures, some organic salts
are liquid at room temperature and below.
Those are called room-temperature ionic
liquids and are attractive as electrolytes in
batteries and electrochemical capacitors,
because they do not have a solvent that
may evaporate or catch fire, they are
not flammable and they are more stable
than solutions of salts in water or organic
solvents when an electric field is applied.
As Professor of Materials Science and
Engineering, your interest in nanotechnology
is well-founded. What inspired your career in
this field of expertise?
Since my high school years, I have been
interested in chemistry and high-temperatures.
High-temperature processes were my passion
in the Chemistry Club in high school and I
continue to be excited about this subject.
This led me to study metallurgy at the Kiev
Polytechnic, which in my opinion is the best
technical university in Ukraine, selecting hightemperature materials as the subject of my PhD
work, and later moving to the nanomaterials
field. I am now a Distinguished University
Professor and Trustee Chair, directing the A
J Drexel Nanotechnology Institute at Drexel
University, and my work is now focused around
researching nanomaterials, many of which are
produced at high temperatures.
FIGURE 1. Schematic of a supercapacitor electrode (carbon particles on a
metal current collector) and a magnified picture of electrolyte ions between
carbon pore walls.
What instigated the
collaboration between
Drexel Nanotechnology
Institute and the Imperial
College of London? How
are you benefiting from the
partnership?
My Nanomaterials Group
primarily performs
experimental research.
However, it is very difficult
to understand phenomena at
the nanoscale without a solid
theory base. Modelling and
simulation help immensely
to explain the processes
that govern charge storage
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INTERNATIONAL INNOVATION
in electrochemical
capacitors at the
nanometre (one
billionth of a metre)
scale and develop
better devices. Therefore,
supported by a grant
from the National Science
Foundation-UK International Collaborations
in Chemistry programme, we combined
efforts with Professor Alexei Kornyshev’s
group. He is one of the world’s leading
theoretical electrochemists. His insights
help us to understand ions’ behaviour
at the electrochemical interfaces and
move towards the development of better
materials and material architectures for
electrochemical capacitors, also known as
supercapacitors or ultracapacitors.
Have you obtained any positive results from
your investigations?
Yes, we have made significant progress
towards working jointly and in parallel in the
same direction with our partners. Kornyshev
directed his efforts toward development
of the theory explaining behaviour of ionic
liquids in pores so narrow that just one or a
few ions can fit between graphitic walls. My
research group performed experiments to
help understand ionic liquids confined in pores
of carbon or at the interfaces with various
carbons and compare those results with the
work done by Kornyshev’s group. For example,
in a joint paper titled ‘Effect of pore size and its
dispersity on the energy storage in nanoporous
supercapacitors’, that was published in the
high-impact journal of the Royal Society of
PROFESSOR YURY GOGOTSI
Global
collaboration
in chemical
nanotechnology
A J Drexel Nanotechnology Institute is teaming
up with research institutions and international
industry groups to explore ways to increase the commercial application
of new nanomaterials, particularly within the energy storage sector
Chemistry, Energy &
Environmental Science, we were
able to provide experimental
verification of the pore size effect
on differential capacitance and
demonstrate that variation of pores
in real materials (not all pores are of
exactly the same size) may be responsible
for discrepancies between the theory and
experiment and between data published by
different research groups.
Who are the main collaborators on your
latest project? How are they contributing to
your overall aims?
Kornyshev is obviously the main collaborator,
as we have a joint grant. He visited Drexel
University and he met with my students on
several occasions. We also met at conferences
in Europe that my students and I attended. We
keep in touch using Skype conferences together
with his postdoctorate student Slavko Kondrat.
However, the National Science Foundation
grant facilitated our collaboration with other
European researchers and, as a result, we
published research papers with Professor
Maxim Fedorov (Strathclyde University, UK),
Professor Mathieu Salanne (University of
Paris), Professor Paul A Madden (University of
Oxford), Professor Patrice Simon (Paul Sabatier
University, France), Dr Magali Brunet (CNRS,
France) and Professor Clare Grey (Cambridge
University) in the past two years. Those
researchers have complementary expertise
in molecular dynamics or experimental
techniques that our group lacks. Together we
can target complex problems that none of us
would be able to solve alone.
RESEARCHING THE FUNDAMENTALS
of
nanomaterials,
nanoparticles
and
composites is complex and expensive.
Utilising this knowledge and transferring it
into practical applications for commercial
use is a significant undertaking, but it is a
task that the Nanomaterials Group at Drexel
University in Philadelphia, USA, is proud to
be leading. The Group’s research focuses on
advancing innovative nanomaterials. Professor
Yury Gogotsi, based at Drexel University’s
Department of Materials Science and
Engineering, is leading a global collaboration
that is researching how ionic liquids behave
and act in confined environments. He
and his collaborators strive to understand
fundamental science, but also use the acquired
knowledge for developing new materials
and devices. Research activities focus on the
synthesis, modification and application of
nanostructured carbons, including nanotubes,
porous carbon networks, nanodiamond,
graphene and onion-like carbon and related
nanomaterials. Through this work they are
delving into how nanomaterials can be used
in applications within a range of different
sectors: “We primarily target energy-related
applications at the moment, such as capacitive
and chemical energy storage, but biomedical
and other applications of carbon nanomaterials
are being explored as well,” Gogotsi explains.
This work is supported by funding from the US
National Science Foundation-UK International
Collaborations in Chemistry programme.
APPLYING MOLECULAR TECHNIQUES
There are a range of different methods that can
be applied to elucidate how room temperature
ionic liquids behave in electrochemical
capacitors. Because the Nanomaterials Group
is working with porous carbon materials, that
are like sponges with pores as small as single
ions (which are less than one billionth of a
metre in diametre), they are employing indirect
methods for researching these materials. “It
is impossible to see with the naked eye or
even an electron microscope the behaviour of
single ions in pores,” points out Gogotsi. As a
result they are using molecular techniques to
help explore the behaviour and reactions of
ionic liquids in these confined environments.
The researchers are using the electrochemical
characterisation of materials in ionic liquids
to investigate how much charge can be
stored when certain voltages are applied. This
is vital because they will need to be aware of
the maximum voltage that can be applied in
order to avoid any electrode material damage
or decomposition of the ionic liquid that will
lead to a shorter lifetime of the device. In
addition to the lifetime, safety is also of great
importance for most industrial applications and
one of the benefits of ionic liquids is that they
are not flammable, which makes them highly
attractive for very large supercapacitors and
energy storage devices.
EXPLORING SUPERCAPACITORS
Domestic solar energy is one of the most
promising areas of expansion for technologies
such as those being worked on by the
Nanomaterials Group. A major challenge for
Gogotsi’s team is finding a way to store the very
energy that renewable energy devices produce.
They are looking at ways to enhance and improve
electrical energy storage devices, including
electrochemical capacitors, batteries and their
hybrids. One device of particular interest is
the supercapacitor, which stores energy in an
electric double layer. Because supercapacitors
have a high power density and can deliver a
steady output for up to a million charge and
WWW.RESEARCHMEDIA.EU 89
INTELLIGENCE
IONIC LIQUID IN CONFINED
ENVIRONMENTS
OBJECTIVES
The goal is to conduct experiments and
molecular simulations to elucidate the
mechanisms of surface charging and
discharging in electrochemical capacitors
with room temperature ionic liquid
electrolytes. Energy storage mechanisms
and current delivery dynamics, as well as the
behaviour of ions in nanoscale confinement,
are being investigated. Understanding the
interaction between ions and nanostructured
carbon surfaces is essential for the
development of supercapacitors for electrical
energy storage and harvesting applications.
KEY COLLABORATORS
Professor Alexei Kornyshev, Imperial
College, London, UK
Professor Patrice Simon, Paul Sabatier
University, Toulouse, France
FUNDING
US National Science Foundation –
International Collaboration in Chemistry
award no. 0924570
CONTACT
Dr Yury Gogotsi
Distinguished University Professor and
Trustee Chair
Drexel University
Department of Materials Science and
Engineering
3141 Chestnut Street
Philadelphia
Pennsylvania 19104
USA
T +1 215 895 6446
E gogotsi@drexel.edu
nano.materials.drexel.edu
YURY GOGOTSI is a Distinguished
University Professor and Trustee Chair of
Materials Science and Engineering at Drexel
University. He also serves as Director of the
A J Drexel Nanotechnology Institute. His
research group works on nanostructured
carbons, two-dimensional metal carbides
(MXenes) and other nanomaterials. Gogotsi
has co-authored two books, edited 10
books, obtained more than 30 patents and
authored about 300 research papers. He
currently serves as an editor of CARBON
(Elsevier) and is a member of the editorial
board of several other journals.
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INTERNATIONAL INNOVATION
The world needs to learn how
to design at the nanometre and
even subnanometre scale, build
materials, structures and devices at
the molecular level to help resolve
some of the significant issues
society is currently facing
of power as well as increased energy storage.
It is hoped that this particular line of study will
allow the researchers to explain how fast ions
can move through complex networks of pores
in carbon electrode materials.
FUTURE POTENTIAL
FOR NANOTECHNOLOGY
Drexel University is well-placed to help lead the
global development of nanotechnologies into
the future. There are over 30 professors based
at the University who are investigating a range
of aspects of nanotechnology, many of which
will very likely have practical application for
a variety of different industrial sectors. From
Gogotsi’s perspective, it is important to focus
on progressing with technologies that are most
likely to have the biggest impact on the world,
such as the provision of energy, the supply of
drinking water and improving human health.
He considers these to be problems that cannot
be solved without pushing the limits of current
knowledge in nanoscience to help search out and
develop new engineering solutions. “The world
needs to learn how to design at the nanometre
and even subnanometre scale, build materials,
structures and devices at the molecular level
to help resolve some of the significant issues
society is currently facing,” he underlines. This
is exactly where the Drexel scientists are now
applying their research energies.
discharge cycles, they are considered to be an
important technology for future energy supply.
Whilst supercapacitors have many advantages
with regard to batteries, they also currently
suffer from a limited amount of stored
energy. Gogotsi believes that researching the
correlation between pore and ion size will
enable the use of ionic liquid electrolytes that
have a higher operating voltage, and packing
as many ions as possible into each electrode:
“This is essential for pushing supercapacitors
closer to batteries, which currently have a
significantly higher energy density,” he asserts.
The researchers have already demonstrated
that the energy density of supercapacitors
can be improved significantly by optimising
the pore size of carbon
electrodes to match a
FIGURE 2. Atomic structures of silicon carbide and carbons (tripple-wall
given electrolyte.
nanotube, folded graphene, onion and porous amorphous network) produced
by extracting silicon from the carbide (© Dr Vadym Mochalin).
In these investigations
theory and experiments
are united to enable
the scientists to explain
exactly what ‘the best
pore size’ means with
regard to operating
voltage and dispersion
of pore size. They have
observed that higher
voltages favour bigger
pore sizes for maximum
charge storage, thus
a larger dispersion of
pore sizes is considered
to be harmful to
the
energy density.
Supercapacitors are part
of the electric energy
storage
technologies
which Gogotsi considers
to be a ‘bottleneck
technology’ for the
wide use of intermittent
energy
production
from renewable energy
sources.
Another
field of research the
Nanomaterials Group is
currently investigating
is the dynamics of
charging-discharging,
which it sees as vital to
explaining whether the
nanoconfinement also
impacts on the delivery