Tag Archives: buckminsterfullerene

Psst: secret marriage … Buckyballs and Graphene get together!

A March 1, 2018 news item on Nanowerk announces  a new coupling,

Scientists combined buckyballs, [also known as buckminsterfullerenes, fullerenes, or C60] which resemble tiny soccer balls made from 60 carbon atoms, with graphene, a single layer of carbon, on an underlying surface. Positive and negative charges can transfer between the balls and graphene depending on the nature of the surface as well as the structural order and local orientation of the carbon ball. Scientists can use this architecture to develop tunable junctions for lightweight electronic devices.

The researchers have made this illustration of their work available,

Researchers are developing new, lightweight electronics that rapidly conduct electricity by covering a sheet of carbon (graphene) with buckyballs. Electricity is the flow of electrons. On these lightweight structures, electrons as well as positive holes (missing electrons) transfer between the balls and graphene. The team showed that the crystallinity and orientation of the balls, as well as the underlying layer, affected this charge transfer. The top image shows a calculation of the charge density for a specific orientation of the balls on graphene. The blue represents positive charges, while the red is negative. The bottom image shows that the balls are in a close-packed structure. The bright dots correspond to the projected images of columns of buckyball molecules. Courtesy: US Department of Energy Office of Science

A February 28, 2018 US Department of Energy (DoE) Office of Science news release, which originated the news item, provides more detail,

The Impact

Fast-moving electrons and their counterpart, holes, were preserved in graphene with crystalline buckyball overlayers. Significantly, the carbon ball provides charge transfer to the graphene. Scientists expect the transfer to be highly tunable with external voltages. This marriage has ramifications for smart electronics that run longer and do not break as easily, bringing us closer to sensor-embedded smart clothing and robotic skin.

Summary

Charge transfer at the interface between dissimilar materials is at the heart of almost all electronic technologies such as transistors and photovoltaic devices. In this study, scientists studied charge transfer at the interface region of buckyball molecules deposited on graphene, with and without a supporting substrate, such as hexagonal boron nitride. They employed ab initio density functional theory with van der Waals interactions to model the structure theoretically. Van der Waals interactions are weak connections between neutral molecules. The team used high-resolution transmission electron microscopy and electronic transport measurements to characterize experimentally the properties of the interface. The researchers observed that charge transfer between buckyballs and the graphene was sensitive to the nature of the underlying substrate, in addition, to the crystallinity and local orientation of the buckyballs. These studies open an avenue to devices where buckyball layers on top of graphene can serve as electron acceptors and other buckyball layers as electron donors. Even at room temperature, buckyball molecules were orientationally locked into position. This is in sharp contrast to buckyball molecules in un-doped bulk crystalline configurations, where locking occurs only at low temperature. High electron and hole mobilities are preserved in graphene with crystalline buckyball overlayers. This finding has ramifications for the development of organic high-mobility field-effect devices and other high mobility applications.

Here’s a link to and a citation for the paper,

Molecular Arrangement and Charge Transfer in C60 /Graphene Heterostructures by Claudia Ojeda-Aristizabal, Elton J. G. Santos, Seita Onishi, Aiming Yan, Haider I. Rasool, Salman Kahn, Yinchuan Lv, Drew W. Latzke, Jairo Velasco Jr., Michael F. Crommie, Matthew Sorensen, Kenneth Gotlieb, Chiu-Yun Lin, Kenji Watanabe, Takashi Taniguchi, Alessandra Lanzara, and Alex Zettl. ACS Nano, 2017, 11 (5), pp 4686–4693 DOI: 10.1021/acsnano.7b00551 Publication Date (Web): April 24, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

R.I.P. Mildred Dresselhaus, Queen of Carbon

I’ve been hearing about Mildred Dresselhaus, professor emerita (retired professor) at the Massachusetts Institute of Technology (MIT), just about as long as I’ve been researching and writing about nanotechnology (about 10 years including the work for my master’s project with the almost eight years on this blog).

She died on Monday, Feb. 20, 2017 at the age of 86 having broken through barriers for those of her gender, barriers for her subject area, and barriers for her age.

Mark Anderson in his Feb. 22, 2017 obituary for the IEEE (Institute of Electrical and Electronics Engineers) Spectrum website provides a brief overview of her extraordinary life and accomplishments,

Called the “Queen of Carbon Science,” Dresselhaus pioneered the study of carbon nanostructures at a time when studying physical and material properties of commonplace atoms like carbon was out of favor. Her visionary perspectives on the sixth atom in the periodic table—including exploring individual layers of carbon atoms (precursors to graphene), developing carbon fibers stronger than steel, and revealing new carbon structures that were ultimately developed into buckyballs and nanotubes—invigorated the field.

“Millie Dresselhaus began life as the child of poor Polish immigrants in the Bronx; by the end, she was Institute Professor Emerita, the highest distinction awarded by the MIT faculty. A physicist, materials scientist, and electrical engineer, she was known as the ‘Queen of Carbon’ because her work paved the way for much of today’s carbon-based nanotechnology,” MIT president Rafael Reif said in a prepared statement.

Friends and colleagues describe Dresselhaus as a gifted instructor as well as a tireless and inspired researcher. And her boundless generosity toward colleagues, students, and girls and women pursuing careers in science is legendary.

In 1963, Dresselhaus began her own career studying carbon by publishing a paper on graphite in the IBM Journal for Research and Development, a foundational work in the history of nanotechnology. To this day, her studies of the electronic structure of this material serve as a reference point for explorations of the electronic structure of fullerenes and carbon nanotubes. Coauthor, with her husband Gene Dresselhaus, of a leading book on carbon fibers, she began studying the laser vaporation of carbon and the “carbon clusters” that resulted. Researchers who followed her lead discovered a 60-carbon structure that was soon identified as the icosahedral “soccer ball” molecular configuration known as buckminsterfullerene, or buckyball. In 1991, Dresselhaus further suggested that fullerene could be elongated as a tube, and she outlined these imagined objects’ symmetries. Not long after, researchers announced the discovery of carbon nanotubes.

When she began her nearly half-century career at MIT, as a visiting professor, women consisted of just 4 percent of the undergraduate student population.  So Dresselhaus began working toward the improvement of living conditions for women students at the university. Through her leadership, MIT adopted an equal and joint admission process for women and men. (Previously, MIT had propounded the self-fulfilling prophecy of harboring more stringent requirements for women based on less dormitory space and perceived poorer performance.) And so promoting women in STEM—before it was ever called STEM—became one of her passions. Serving as president of the American Physical Society, she spearheaded and launched initiatives like the Committee on the Status of Women in Physics and the society’s more informal committees of visiting women physicists on campuses around the United States, which have increased the female faculty and student populations on the campuses they visit.

If you have the time, please read Anderson’s piece in its entirety.

One fact that has impressed me greatly is that Dresselhaus kept working into her eighties. I featured a paper she published in an April 27, 2012 posting at the age of 82 and she was described in the MIT write up at the time as a professor, not a professor emerita. I later featured Dresselhaus in a May 31, 2012 posting when she was awarded the Kavli Prize for Nanoscience.

It seems she worked almost to the end. Recently, GE (General Electric) posted a video “What If Scientists Were Celebrities?” starring Mildred Dresselhaus,

H/t Mark Anderson’s obituary Feb. 22, 2017 piece. The video was posted on Feb. 8, 2017.

Goodbye to the Queen of Carbon!

#BCTECH: being at the Summit (Jan. 18-19, 2016)

#BCTECH Summit 2016*, a joint event between the province of British Columbia (BC, Canada) and the BC Innovation Council (BCIC), a crown corporation formerly known as the Science Council of British Columbia, launched on Jan. 18, 2016. I have written a preview (Jan. 17, 2016 post) and a commentary on the new #BCTECH strategy (Jan. 19, 2016 posting) announced by British Columbia Premier, Christy Clark, on the opening day (Jan. 18, 2016) of the summit.

I was primarily interested in the trade show/research row/technology showcase aspect of the summit focusing (but not exclusively) on nanotechnology. Here’s what I found,

Nano at the Summit

  • Precision NanoSystems: fabricates equipment which allows researchers to create polymer nanoparticles for delivering medications.

One of the major problems with creating nanoparticles is ensuring a consistent size and rapid production. According to Shell Ip, a Precision NanoSystems field application scientist, their NanoAssemblr Platform has solved the consistency problem and a single microfluidic cartridge can produce 15 ml in two minutes. Cartridges can run in parallel for maximum efficiency when producing nanoparticles in greater quantity.

The NanoAssemblr Platform is in use in laboratories around the world (I think the number is 70) and you can find out more on the company’s About our technology webpage,

The NanoAssemblr™ Platform

The microfluidic approach to particle formulation is at the heart of the NanoAssemblr Platform. This well-controlled process mediates bottom-up self-assembly of nanoparticles with reproducible sizes and low polydispersity. Users can control size by process and composition, and adjust parameters such as mixing ratios, flow rate and lipid composition in order to fine-tune nanoparticle size, encapsulation efficiency and much more. The system technology enables manufacturing scale-up through microfluidic reactor parallelization similar to the arraying of transistors on an integrated chip. Superior design ensures that the platform is fast and easy to use with a software controlled manufacturing process. This usability allows for the simplified transfer of manufacturing protocols between sites, which accelerates development, reduces waste and ultimately saves money. Precision NanoSystems’ flagship product is the NanoAssemblr™ Benchtop Instrument, designed for rapid prototyping of novel nanoparticles. Preparation time on the system is streamlined to approximately one minute, with the ability to complete 30 formulations per day in the hands of any user.

The company is located on property known as the Endowment Lands or, more familiarly, the University of British Columbia (UBC).

A few comments before moving on, being able to standardize the production of medicine-bearing nanoparticles is a tremendous step forward which is going to help scientists dealing with other issues. Despite all the talk in the media about delivering nanoparticles with medication directly to diseased cells, there are transport issues: (1) getting the medicine to the right location/organ and (2) getting the medicine into the cell. My Jan. 12, 2016 posting featured a project with Malaysian scientists and a team at Harvard University who are tackling the transport and other nanomedicine) issues as they relate to the lung. As well, I have a Nov. 26, 2015 posting which explores a controversy about nanoparticles getting past the ‘cell walls’ into the nucleus of the cell.

The next ‘nano’ booths were,

  • 4D Labs located at Simon Fraser University (SFU) was initially hailed as a nanotechnology facility but these days they’re touting themselves as an ‘advanced materials’ facility. Same thing, different branding.

They advertise services including hands-on training for technology companies and academics. There is a nanoimaging facility and nanofabrication facility, amongst others.

I spoke with their operations manager, Nathaniel Sieb who mentioned a few of the local companies that use their facilities. (1) Nanotech Security (featured here most recently in a Dec. 29, 2015 post), an SFU spinoff company, does some of their anticounterfeiting research work at 4D Labs. (2) Switch Materials (a smart window company, electrochromic windows if memory serves) also uses the facilities. It is Neil Branda’s (4D Labs Executive Director) company and I have been waiting impatiently (my May 14, 2010 post was my first one about Switch) for either his or someone else’s electrochromic windows (they could eliminate or reduce the need for air conditioning during the hotter periods and reduce the need for heat in the colder periods) to come to market. Seib tells me, I’ll have to wait longer for Switch. (3) A graduate student was presenting his work at the booth, a handheld diagnostic device that can be attached to a smartphone to transmit data to the cloud. While the first application is for diabetics, there are many other possibilities. Unfortunately, glucose means you need to produce blood for the test when I suggested my preference for saliva the student explained some of the difficulties. Apparently, your saliva changes dynamically and frequently and something as simple as taking a sip of orange juice could result in a false reading. Our conversation (mine, Seib’s and the student’s) also drifted over into the difficulties of bringing products to market. Sadly, we were not able to solve that problem in our 10 minute conversation.

  • FPInnovations is a scientific research centre and network for the forestry sector. They had a display near their booth which was like walking into a peculiar forest (I was charmed). The contrast with the less imaginative approaches all around was striking.

FPInnovation helped to develop cellulose nanocrystals (CNC), then called nanocrystalline cellulose (NCC), and I was hoping to be updated about CNC and about the spinoff company Celluforce. The researcher I spoke to was from Sweden and his specialty was business development. He didn’t know much about CNC in Canada and when I commented on how active Sweden has been its pursuit of a CNC application, he noted Finland has been the most active. The researcher noted that making the new materials being derived from the forest, such as CNC, affordable and easily produced for use in applications that have yet to be developed are all necessities and challenges. He mentioned that cultural changes also need to take place. Canadians are accustomed to slicing away and discarding most of the tree instead of using as much of it as possible. We also need to move beyond the construction and pulp & paper sectors (my Feb. 15, 2012 posting featured nanocellulose research in Sweden where sludge was the base material).

Other interests at the Summit

I visited:

  • “The Wearable Lower Limb Anthropomorphic Exoskeleton (WLLAE) – a lightweight, battery-operated and ergonomic robotic system to help those with mobility issues improve their lives. The exoskeleton features joints and links that correspond to those of a human body and sync with motion. SFU has designed, manufactured and tested a proof-of-concept prototype and the current version can mimic all the motions of hip joints.” The researchers (Siamak Arzanpour and Edward Park) pointed out that the ability to mimic all the motions of the hip is a big difference between their system and others which only allow the leg to move forward or back. They rushed the last couple of months to get this system ready for the Summit. In fact, they received their patent for the system the night before (Jan. 17, 2016) the Summit opened.

It’s the least imposing of the exoskeletons I’ve seen (there’s a description of one of the first successful exoskeletons in a May 20, 2014 posting; if you scroll down to the end you’ll see an update about the device’s unveiling at the 2014 World Cup [soccer/football] in Brazil).

Unfortunately, there aren’t any pictures of WLLAE yet and the proof-of-concept version may differ significantly from the final version. This system could be used to help people regain movement (paralysis/frail seniors) and I believe there’s a possibility it could be used to enhance human performance (soldiers/athletes). The researchers still have some significant hoops to jump before getting to the human clinical trial stage. They need to refine their apparatus, ensure that it can be safely operated, and further develop the interface between human and machine. I believe WLLAE is considered a neuroprosthetic device. While it’s not a fake leg or arm, it enables movement (prosthetic) and it operates on brain waves (neuro). It’s a very exciting area of research, consequently, there’s a lot of international competition.

  • Delightfully, after losing contact for a while, I reestablished it with the folks (Sean Lee, Head External Relations and Jim Hanlon, Chief Administrative Officer) at TRIUMF (Canada’s national laboratory for particle and nuclear physics). It’s a consortium of 19 Canadian research institutions (12 full members and seven associate members).

It’s a little disappointing that TRIUMF wasn’t featured in the opening for the Summit since the institution houses theoretical, experimental, and applied science work. It’s a major BC (and Canada) science and technology success story. My latest post (July 16, 2015) about their work featured researchers from California (US) using the TRIUMF cyclotron for imaging nanoscale materials and, on the more practical side, there’s a Mar. 6, 2015 posting about their breakthrough for producing nuclear material-free medical isotopes. Plus, Maclean’s Magazine ran a Jan. 3, 2016 article by Kate Lunau profiling an ‘art/science’ project that took place at TRIUMF (Note: Links have been removed),

It’s not every day that most people get to peek inside a world-class particle physics lab, where scientists probe deep mysteries of the universe. In September [2015], Vancouver’s TRIUMF—home to the world’s biggest cyclotron, a type of particle accelerator—opened its doors to professional and amateur photographers, part of an event called Global Physics Photowalk 2015. (Eight labs around the world participated, including CERN [European particle physics laboratory], in Geneva, where the Higgs boson particle was famously discovered.)

Here’s the local (Vancouver) jury’s pick for the winning image (from the Nov. 4, 2015 posting [Winning Photographs Revealed] by Alexis Fong on the TRIUMF website),

Caption: DESCANT (at TRIUMF) neutron detector array composed of 70 hexagonal detectors Credit: Pamela Joe McFarlane

Caption: DESCANT (at TRIUMF) neutron detector array composed of 70 hexagonal detectors Credit: Pamela Joe McFarlane

With all those hexagons and a spherical shape, the DESCANT looks like a ‘buckyball’ or buckminsterfullerene or C60  to me.

I hope the next Summit features TRIUMF and/or some other endeavours which exemplify, Science, Technology, and Creativity in British Columbia and Canada.

Onto the last booth,

  • MITACS was originally one of the Canadian federal government’s Network Centres for Excellence projects. It was focused on mathematics, networking, and innovation but once the money ran out the organization took a turn. These days, it’s describing itself as (from their About page) “a national, not-for-profit organization that has designed and delivered research and training programs in Canada for 15 years. Working with 60 universities, thousands of companies, and both federal and provincial governments, we build partnerships that support industrial and social innovation in Canada.”Their Jan. 19, 2016 news release (coincidental with the #BCTECH Summit, Jan. 18 – 19, 2016?) features a new report about improving international investment in Canada,

    Opportunities to improve Canada’s attractiveness for R&D investment were identified:

    1.Canada needs to better incentivize R&D by rebalancing direct and indirect support measures

    2.Canada requires a coordinated, client-centric approach to incentivizing R&D

    3.Canada needs to invest in training programs that grow the knowledge economy”

    Oddly, entrepreneurial/corporate/business types never have a problem with government spending when the money is coming to them; it’s only a problem when it’s social services.

    Back to MITACS, one of their more interesting (to me) projects was announced at the 2015 Canadian Science Policy Conference. MITACS has inaugurated a Canadian Science Policy Fellowships programme which in its first year (pilot) will see up up to 10 academics applying their expertise to policy-making while embedded in various federal government agencies. I don’t believe anything similar has occurred here in Canada although, if memory serves, the Brits have a similar programme.

    Finally, I offer kudos to Sherry Zhao, MITACS Business Development Specialist, the only person to ask me how her organization might benefit my business. Admittedly I didn’t talk to a lot of people but it’s striking to me that at an ‘innovation and business’ tech summit, only one person approached me about doing business.  Of course, I’m not a male aged between 25 and 55. So, extra kudos to Sherry Zhao and MITACS.

Christy Clark (Premier of British Columbia), in her opening comments, stated 2800 (they were expecting about 1000) had signed up for the #BCTECH Summit. I haven’t been able to verify that number or get other additional information, e.g., business deals, research breakthroughs, etc. announced at the Summit. Regardless, it was exciting to attend and find out about the latest and greatest on the BC scene.

I wish all the participants great and good luck and look forward to next year’s where perhaps we’ll here about how the province plans to help with the ‘manufacturing middle’ issue. For new products you need to have facilities capable of reproducing your devices at a speed that satisfies your customers; see my Feb. 10, 2014 post featuring a report on this and other similar issues from the US General Accountability Office.

*’BCTECH Summit 2016′ link added Jan. 21, 2016.

A trio of nano news items from Japan (Irago Conference 2015, novel tuneable metallofullerenes, and nanoislands and skeletal skin for fuel cells)

Getting onto a list for news releases from Japan has been a boon. I don’t know how it happened but now I can better keep up with the nanotechnology effort in the country where the term was first coined (Norio Taniguchi) and which is a research leader in this field.

Irago Conference

This is a very intriguing conference, from a joint Oct. 18, 2015 Toyohashi University of Technology and University of Electro-Communications press release,

Organized by the Toyohashi University of Technology and University of Electro-Communications, Tokyo, the Irago Conference aims to enhance mutual understanding between scientists, engineers, policy makers, and experts from a wide spectrum of pure and applied sciences in order to resolve major global issues.

The Irago Conference 2015 is a unique conference combining thought provoking insights into global issues including disaster mitigation, neuroscience, public health monitoring, and nanotechnology [emphasis mine] by internationally renowned invited speakers with selected talks, posters, and demonstrations from academics, industrialists, and think tanks. The conference is truly a ‘360 degree outlook on critical scientific and technological challenges’ facing mankind.

Recent changes in global economics and industrial priorities, environmental and energy policies, food production and population movements have produced formidable challenges that must be addressed for sustaining life on earth.

The Irago Conference will highlight the major issues by bringing together experts from across the world who will give their views on key areas such as energy and natural resources, medicine and public health, disaster prevention and management, as well as other advances in science, technology and life sciences.

Observation, measurement, and monitoring are the keywords of the core topics covered at Irago 2015 with invited speakers Professor Masashi Hayakawa (University of Electro-Communications, Japan) presenting his pioneering research on “Earthquake prediction with electromagnetic phenomena, and Nobuhiko Okabe  (Kawasaki City Institute for Public Health, Japan) discussing “The role and contribution of Kawasaki City Institute for Public Health (Local Public Health Laboratory), locally and globally” with first hand examples of monitoring food safety and the spread of possible diseases carried by insects.

The Irago Conference will be streamed live. Visit the conference website for the links to the streaming site.

http://iragoconference.jp/

When: Thursday, 22 October 2015 to Friday 23  October 2015.

Where: Irago Sea-Park & Spa Hotel, Tahara, Aichi, Japan

They don’t appear to have set up the streaming link yet.

Tuneable metallofullerenes

Originally issued as a Sept. 21, 2015 press release, the University of Electro-Communications has issued an Oct. 19, 2015 version,

Tiny nanoscale molecules in the form of spherical carbon cages, or ‘fullerenes’, have received considerable attention in recent years. Individual or small groups of atoms can be trapped inside fullerenes, creating stable molecules with unique electronic structures and unusual properties that can be exploited in the field of nanomaterials and biomedical science.

Endohedral metallofullerenes (EMFs) are one such class of molecules, in which one or more metal atoms are encapsulated inside many kinds of carbon cages. Crucially, the metal atom(s) are not chemically bonded with the carbon surrounds, but they do donate electrons to the carbon cage. Scientists have recently begun to understand how to control the movement, behavior and positioning of the enclosed atoms by adding other atoms, such as silicon or germanium (in their silyl or germyl groups), to the fullerene surface. This allows for the manipulation and fine-tuning of the EMF’s properties.

Now, Masahiro Kako and co-workers at the University of Electro-Communications in Tokyo, together with scientists across Japan and the USA, have created and analyzed the effects of silylation and germylation on an EMF called Lu3N@Ih-C80 (three lutetium atoms bonded to a nitrogen atom encased inside a carbon 80 cage).

Using X-ray crystallography, electrochemical analyses and theoretical calculations, the team discovered that adding silyl groups or germyl groups to the fullerene structure was a versatile way of controlling the EMF’s electronic properties. The exact positioning of the silyl or germyl groups in bonding to the carbon structure determined the energy gaps present in the EMF, and determined the orientation of the bonded metal atoms inside the cage.

The germyl groups donated more electrons and the process worked slightly more efficiently than the silyl groups, but Kako and his team believe that both provide an effective way of fine-tuning EMF electronic characteristics.

Background

A brief history of fullerenes

Fullerenes are carbon molecules that take the shape of spheres. The most famous and abundant fullerene is the buckminsterfullerene, or ‘buckyball’, C60, which resembles a soccer ball in shape with a bonded carbon atom at each point of every polygon.

Endohedral metallofullerenes, or EMFs, are created by trapping a metal atom or atoms inside a fullerene cage, rather like a hamster in a ball. The trapped atom(s) are not chemically-bonded to the carbon, but they do interact with it by donating electrons, thus creating unique and very useful molecules for nanomaterial science and biomedicine.

Silylation and germylation

The addition of other atoms to fullerene surfaces can affect EMF properties, by regulating the behavior of the metal atoms inside the fullerene cage. In one EMF, the movement of lanthanum atoms is restricted to two dimensions by the addition of silyl groups to the carbon cage. This alters the electrostatic potentials inside the cage and restricts the lanthanum atoms’ mobility, and thus changes the overall properties of the whole molecule.

This study by Masahiro Kako and co-workers further enhances understanding of the effects of silylation and germalytion (the addition of silicon-based and germanium-based groups) on lutetium-based EMFs. The team have shown that the exact positioning of the additional atoms in the carbon structure can influence the energy gaps across the molecule, thereby allowing them to tune the electronic properties of the EMF. This ability to ‘fine-tune’ EMFs could have some applications for functional materials in molecular electronics, such as acceptors in organic photovoltaic devices.

Further work

Kako and his team hope to carry out further investigations into the addition of alternative groups of atoms to fullerenes, to add to the tuning properties of silicon- and germanium-based groups. This could expand on the versatility of EMFs and their potential applications in future.

Fullerenes don’t get that much attention these days when compared to graphene and carbon nanotubes although there seems to be increasing interest in their potential as cages.

Here’s a link to and a citation for the paper,

Preparation, Structural Determination, and Characterization of Electronic Properties of Bis-Silylated and Bis-Germylated Lu3N@Ih-C80 by Prof. Dr. Masahiro Kako, Kyosuke Miyabe, Dr. Kumiko Sato, Dr. Mitsuaki Suzuki, Dr. Naomi Mizorogi, Dr. Wei-Wei Wang, Prof. Dr. Michio Yamada, Prof. Dr. Yutaka Maeda, Prof. Dr. Marilyn M. Olmstead, Prof. Dr. Alan L. Balch, Prof. Dr. Shigeru Nagase, and Prof. Dr. Takeshi Akasaka. Chemistry – A European Journal DOI: 10.1002/chem.201503579 Article first published online: 21 SEP 2015

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Nanoislands and skeletal skin for fuel cells

This final item concerns a platinum ‘skin’. From an Oct. 21, 2015 University of Electro-Communications press release,

Polymer electrolyte fuel cells (PEFC) could provide an alternative to traditional fossil fuel power, but higher performance and durability under harsh conditions are needed before PEFC vehicles can be considered commercially viable. Now researchers at the University of Electro-Communications, the University of Tokushima and Japan Synchrotron Radiation Research Institute in Japan have synthesised catalysts from platinum cobalt (PtCo3) nanoparticles on carbon (C) with tin oxide (SnO2) nanoislands and shown that they perform better than any previously reported.

Fuel cell research has focused on platinum alloys and transition metal oxides to improve on the durability and catalytic performance of platinum on carbon. Previous work with SnO2 islands grown on platinum tin alloy with carbon had already shown some improvement in the oxygen reduction reactions that occur in fuel cells. However growing islands of only SnO2 on other alloys posed a challenge.

Now Yasuhiro Iwasawa at the University of Electro-Communications and his colleagues have grown SnO2 islands on Pt3Co nanoparticles on carbon (Pt3Co/C) by selective electrochemical deposition of tin metal, which is then oxidized. The addition of the SnO2 nanoislands doubled the catalytic performance of the Pt3Co/C catalysts. In addition they were undamaged after undergoing 5000 cycles of voltage changes to test their durability.

The structure the Pt3Co nanoparticles form has a Pt3Co core surrounded by a platinum skin that has a rough – “skeleton” – morphology. The researchers attribute the high catalytic performance in part to efficient electronic modification specifically at the platinum skin surface, and in particular to the unique property of the SnO2 nanoislands at the compressive platinum skeleton-skin surface.

“In general, adhesion of transition metal oxides on carbon induces depression of the electrical conductivity of the carbon,” explain the researchers in their report. “Hence, the selective nano-SnO2 decoration on the Pt-enriched-surface nanoparticles provides a significant advantage as a cathode catalyst.”

Background

Polymer electrolyte fuel cells

Polymer electrolyte fuel cells consist of two porous polymer membranes. On one side hydrogen gas molecules give up electrons and on the other oxygen gas molecules accept electrons completing a current circuit.  The ions can then penetrate the membrane and combine to form water.

Polymer electrolyte fuel cells have several advantages over conventional fuel as they do not deplete the limited supplies of fossil fuels, and the waste products are water and heat, and therefore relatively non-polluting. The efficiency of fuel cells has already highlighted their potential for powering small vehicles.

Redox

The formation of hydrogen and oxygen ions from the gas molecules are referred to as redox reactions from the term ‘reduction’ and ‘oxidation’. In fuel cells neutral oxygen molecules are reduced to negatively charge oxygen ions with a charge of -2. The oxidation number is thus ‘reduced’ from 0 to -2. In contrast, ionisation of hydrogen molecules to positively charge hydrogen ions (that is single protons) increases the oxygen number by one – ‘oxidation’.

Catalysts are used to increase the efficiency of the redox reactions in fuel cells to improve the power and current density. The efficiency of the catalysts is measured in terms of the oxygen reduction reaction (ORR) activity.

Improving ORR

The researchers measured the potential difference required for other reactions in the presence of their catalyst to determine how the additional SnO2 islands improved the ORR. Their observations suggest that strain at the nanoislands on the Pt3Co nanoparticles modifies the electronic structure so that the centre of the electron d band is decreased. This decreases oxygen adsorption and improves the performance of the catalyst. In addition there is an increase in the proton affinity of the platinum near the nanoislands, which significantly enhances the ORR further still.

Here’s a link to and a citation for the paper,

Surface-Regulated Nano-SnO2/Pt3Co/C Cathode Catalysts for Polymer Electrolyte Fuel Cells Fabricated by a Selective Electrochemical Sn Deposition Method by Kensaku Nagasawa, Shinobu Takao, Shin-ichi Nagamatsu, Gabor Samjeské, Oki Sekizawa, Takuma Kaneko, Kotaro Higashi, Takashi Yamamoto, Tomoya Uruga†, and Yasuhiro Iwasawa. J. Am. Chem. Soc., 2015, 137 (40), pp 12856–12864 DOI: 10.1021/jacs.5b04256 Publication Date (Web): September 27, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.