Platinum-graphene fuel cell catalysts show superior stability over bulk platinum – Georgia Institute of Tecnology


Seung Soon Jang, an associate professor, Faisal Alamgir, an associate professor, and Ji Il Choi, a postdoctoral researcher, all in Georgia Tech’s School of Materials Science and Engineering, examine a piece of platinum-graphene catalyst. Credit: Allison Carter

Films of platinum only two atoms thick supported by graphene could enable fuel cell catalysts with unprecedented catalytic activity and longevity, according to a study published recently by researchers at the Georgia Institute of Technology.

Platinum is one of the most commonly used catalysts for fuel cells because of how effectively it enables the oxidation reduction reaction at the center of the technology. But its high cost has spurred research efforts to find ways to use smaller amounts of it while maintaining the same .

“There’s always going to be an initial cost for producing a fuel cell with , and it’s important to keep that cost as low as possible,” said Faisal Alamgir, an associate professor in Georgia Tech’s School of Materials Science and Engineering. “But the real cost of a fuel cell system is calculated by how long that system lasts, and this is a question of durability.

“Recently there’s been a push to use catalytic systems without , but the problem is that there hasn’t been a system proposed so far that simultaneously matches the catalytic activity and the durability of platinum,” Alamgir said.

The Georgia Tech researchers tried a different strategy. In the study, which was published on September 18 in the journal Advanced Functional Materialsand supported by the National Science Foundation, they describe creating several systems that used atomically-thin  of platinum supported by a layer of graphene—effectively maximizing the total surface area of the platinum available for catalytic reactions and using a much smaller amount of the precious metal.

Most platinum-based catalytic systems use nanoparticles of the metal chemically bonded to a support surface, where surface atoms of the particles do most of the catalytic work, and the catalytic potential of the atoms beneath the surface is never utilized as fully as the surface atoms, if at all.

This graphic shows how the graphene layer in gray provides structure and stability to the two atomic layers of platinum above represented in blue. Credit: Ji Il Choi

Additionally, the researchers showed that the new platinum films that are at least two atoms thick outperformed nanoparticle platinum in the dissociation energy, which is a measure of the energy cost of dislodging a surface platinum atom. That measurement suggests those films could make potentially longer-lasting catalytic systems.

To prepare the atomically-thin films, the researchers used a process called electrochemical atomic layer deposition to grow platinum monolayers on a layer of graphene, creating samples that had one, two or three atomic layers of atoms. The researchers then tested the samples for dissociation energy and compared the results to the energy of a single atom of platinum on graphene as well as the energy from a common configurations of platinum nanoparticles used in catalysts.

“The fundamental question at the heart of this work was whether it was possible that a combination of metallic and  can render the platinum atoms in a platinum-graphene combination more stable than their counterparts in bulk platinum used commonly in catalysts that are supported by metallic bonding,” said Seung Soon Jang, an associate professor in the School of Materials Science and Engineering.

The researchers found that the bond between neighboring platinum atoms in the film essentially combines forces with the bond between the film and the graphene layer to provide reinforcement across the system. That was especially true in the platinum film that was two atoms thick.

“Typically metallic films below a certain thickness are not stable because the bonds between them are not directional, and they tend to roll over each other and conglomerate to form a particle,” Alamgir said. “But that’s not true with graphene, which is stable in a two-dimensional form, even one atom thick, because it has very strong covalent directional bonds between its neighboring . So this new catalytic system could leverage the directional bonding of the graphene to support an atomically-thin film of platinum.”

Future research will involve further testing of how the films behave in a catalytic environment. The researchers found in earlier research on graphene-platinum films that the material behaves similarly in catalytic reactions regardless of which side—graphene or platinum—is the exposed active surface.

“In this configuration, the graphene is not acting as a separate entity from the platinum,” Alamgir said. “They’re working together as one. So we believe that if you’re exposing the  side, you get the same catalytic activity and you could further protect the platinum, potentially further enhancing durability.”

More information: Ji Il Choi et al, Contiguous and Atomically Thin Pt Film with Supra‐Bulk Behavior Through Graphene‐Imposed Epitaxy, Advanced Functional Materials(2019).  DOI: 10.1002/adfm.201902274

Journal information: Advanced Functional Materials

Provided by Georgia Institute of Technology

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Why Asia’s biggest economies are backing hydrogen fuel cell cars


 

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FILE PHOTO: An Air Liquide hydrogen station for hydrogen fuel cell cars is seen in Paris, France, October 13, 2016. REUTERS/Charles Platiau. 

China, Japan and South Korea have set ambitious targets to put millions of hydrogen-powered vehicles on their roads by the end of the next decade at a cost of billions of dollars.

But to date, hydrogen fuel cell vehicles (FCVs) have been upstaged by electric vehicles, which are increasingly becoming a mainstream option due to the success of Tesla Inc’s (TSLA.O) luxury cars as well as sales and production quotas set by China.

Critics argue FCVs may never amount to more than a niche technology. But proponents counter hydrogen is the cleanest energy source for autos available and that with time and more refueling infrastructure, it will gain acceptance.

AMBITIOUS TARGETS

China, far and away the world’s biggest auto market with some 28 million vehicles sold annually, is aiming for more than 1 million FCVs in service by 2030. That compares with just 1,500 or so now, most of which are buses.

fuel-cell-market4Read More: Fuel Cell Market by Type

Japan, a market of more than 5 million vehicles annually, wants to have 800,000 FCVs sold by that time from around 3,400 currently.

South Korea, which has a car market just one third the size of Japan, has set a target of 850,000 vehicles on the road by 2030. But as of end-2018, fewer than 900 have been sold.

 

WHY HYDROGEN?

 

Hydrogen’s proponents point to how clean it is as an energy source as water and heat are the only byproducts and how it can be made from a number of sources, including methane, coal, water, even garbage. Resource-poor Japan sees hydrogen as a way to greater energy security.

They also argue that driving ranges and refueling times for FCVs are comparable to gasoline cars, whereas EVs require hours to recharge and provide only a few hundred kilometers of range.

Many backers in China and Japan see FCVs as complementing EVs rather than replacing them. In general, hydrogen is seen as the more efficient choice for heavier vehicles that drive longer distances, hence the current emphasis on city buses.

THE MAIN PLAYERS

Only a handful of automakers have made fuel cell passenger cars commercially available.

Toyota Motor Corp (7203.T) launched the Mirai sedan at the end of 2014, but has sold fewer than 10,000 globally. Hyundai Motor Co (005380.KS) has offered the Nexo crossover since March last year and has sold just under 2,900 worldwide. It had sales of around 900 for its previous FCV model, the Tucson.

Buses are seeing more demand. Both Toyota and Hyundai have offerings and have begun selling fuel cell components to bus makers, particularly in China.

Several Chinese manufacturers have developed their own buses, notably state-owned SAIC Motor (600104.SS), the nation’s biggest automaker, and Geely Auto Group, which also owns the Volvo Cars and Lotus brands.

WHY HAVEN’T FUEL CELL CARS CAUGHT ON YET?

A lack of refueling stations, which are costly to build, is usually cited as the biggest obstacle to widespread adoption of FCVs. At the same time, the main reason cited for the lack of refueling infrastructure is that there are not enough FCVs to make them profitable.

Consumer worries about the risk of explosions are also a big hurdle and residents in Japan and South Korea have protested against the construction of hydrogen stations. This year, a hydrogen tank explosion in South Korea killed two people, which was followed by a blast at a Norway hydrogen station.

Then there’s the cost. Heavy subsidies are needed to bring prices down to levels of gasoline-powered cars. Toyota’s Mirai costs consumers just over 5 million yen ($46,200) after subsidies of 2.25 million yen. That’s still about 50% more than a Camry.

Automakers contend that once sales volumes increase, economies of scale will make subsidies unnecessary.

 

HOW FUEL CELLS WORK

(GRAPHIC: How fuel cell vehicles work: here)

Reuters Graphic

 

Reuters: Reporting by Kevin Buckland in Tokyo; Additional reporting by Yilei Sun in Beijing and Hyunjoo Jin in Seoul; Editing by Edwina Gibbs

 

 

One-atom switch supercharges fluorescent dyes – Rice University


Rice lab discovers simple technique to make biocompatible ‘turn-on’ dyes

It only took the replacement of one atom for Rice University scientists to give new powers to biocompatible fluorescent molecules.

The Rice lab of chemist Han Xiao reported in the Journal of the American Chemical Society it has developed a single-atom switch to turn fluorescent dyes used in biological imaging on and off at will. The technique will enable high-resolution imaging and dynamic tracking of biological processes in living cells, tissues and animals.

The Rice lab developed a minimally modified probe that can be triggered by a broad range of visible light. The patented process could replace existing photoactivatable fluorophores that may only be activated with ultraviolet light or require toxic chemicals to turn on the fluorescence, characteristics that limit their usefulness.

The researchers took advantage of a phenomenon known as photo-induced electron transfer (PET), which was already known to quench fluorescent signals.

Rice University chemist Han Xiao and his colleagues have discovered a simple method to turn fluorescent tags on and off with visible light by switching one atom. (Credit: Jeff Fitlow/Rice University)

Rice University chemist Han Xiao and his colleagues have discovered a simple method to turn fluorescent tags on and off with visible light by switching one atom. Photo by Jeff Fitlow

They put fluorophores in cages of thiocarbonyl, the moeity responsible for quenching. With one-step organic synthesis, they replaced an oxygen atom in the cage with one of sulfur. That enabled them to induce the PET effect to quench fluorescence.

Triggering the complex again with visible light near the fluorescent molecule’s preferred absorbance oxidized the cage in turn. That knocked out the sulfur and replaced it with an oxygen atom, restoring fluorescence.

“All it takes to make these is a little chemistry and one step,” said Xiao, who joined Rice in 2017 with funding from the Cancer Prevention and Research Institute of Texas  (CPRIT). “We demonstrated in the paper that it works the same for a range of fluorescent dyes. Basically, one reaction solves a lot of problems.”

Researchers worldwide use fluorescent molecules to tag and track cells or elements within cells. Activating the tags with low-powered visible light rather than ultraviolet is much less damaging to the cells being studied, Xiao said, and makes the long exposures of living cells required by super-resolution imaging possible.

Super-resolution experiments by Theodore Wensel, the Robert A. Welch Chair in Chemistry at Baylor College of Medicine, and his team confirmed their abilities, he said.

“We feel this will be a really good probe for living-cell imaging,” Xiao said. “People also use photoactivatable dye to track the dynamics of proteins, to see where and how far and how fast they travel. Our work was to provide a simple, general way to generate this dye.”

At top, a sequence shows the design of thio-caged dyes designed at Rice University to be triggered by visible light. At bottom, confocal and super-resolution imaging of a lipid droplet in living adipocytes incubated with BODIPY (green), SNile Red (red) and Hoechst 33342 (blue), followed by photoactivation using a 561 nm laser. Scale bar: 10 µm. Scale bar for super-resolution image of lipid droplet labeled with SNile Red, bottom right: 1 µm. Courtesy of the Xiao Lab

At top, a sequence shows the design of thio-caged dyes designed at Rice University to be triggered by visible light. At bottom, confocal and super-resolution imaging of a lipid droplet in living adipocytes incubated with BODIPY (green), SNile Red (red) and Hoechst 33342 (blue), followed by photoactivation using a 561-nanometer laser. Scale bar: 10 µm. Scale bar for super-resolution image of lipid droplet labeled with SNile Red, bottom right: 1 µm. Courtesy of the Xiao Lab

The researchers found their technique worked on a wide range of common fluorescent tags and could even be mixed for multicolor imaging of targeted molecules in a single cell.

Rice postdoctoral researcher Juan Tang is lead author of the paper. Co-authors are Rice graduate students Kuan-Lin Wu and Jingqi Pei; postdoctoral fellow Michael Robichaux of Baylor; and graduate student Nhung Nguyen and Yubin Zhou, an assistant professor at the Center for Translational Cancer Research at Texas A&M University. Xiao is the Norman Hackerman-Welch Young Investigator and an assistant professor of chemistry, biosciences, and bioengineering.

CPRIT, the Robert A. Welch Foundation, a Hamill Innovation Award, a John S. Dunn Foundation Collaborative Research Award and the National Institutes of Health supported the research.

Stretchy Plastic Electrolytes could Enable NEW lithium-ion Battery Design – Replaces Expensive metals and traditional liquid Electrolyte with Lower Cost transition metal fluorides and a Solid Polymer Electrolyte


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A lithium-ion battery is shown using a promising new cathode and electrolyte system that replaces expensive metals and traditional liquid electrolyte with lower cost transition metal fluorides and a solid polymer electrolyte. Credit: Allison Carter

The growing popularity of lithium-ion batteries in recent years has put a strain on the world’s supply of cobalt and nickel—two metals integral to current battery designs—and sent prices surging.

In a bid to develop alternative designs for lithium-based batteries with less reliance on those , researchers at the Georgia Institute of Technology have developed a promising new  and  system that replaces expensive metals and traditional liquid electrolyte with lower cost transition metal fluorides and a .

“Electrodes made from transition metal fluorides have long shown stability problems and rapid failure, leading to significant skepticism about their ability to be used in next generation batteries,” said Gleb Yushin, a professor in Georgia Tech’s School of Materials Science and Engineering. “But we’ve shown that when used with a solid polymer electrolyte, the metal fluorides show remarkable stability—even at —which could eventually lead to safer, lighter and cheaper lithium-ion batteries.”

In a typical lithium-ion battery, energy is released during the transfer of lithium ions between two electrodes—an anode and a cathode, with a cathode typically comprising lithium and transition metals such as cobalt, nickel and manganese. The ions flow between the electrodes through a liquid electrolyte.

For the study, which was published Sept. 9 in the journal Nature Materials and sponsored by the Army Research Office, the research team fabricated a new type of cathode from iron fluoride active material and a solid polymer electrolyte nanocomposite. Iron fluorides have more than double the lithium capacity of traditional cobalt- or nickel-based cathodes. In addition, iron is 300 times cheaper than cobalt and 150 times cheaper than nickel.

To produce such a cathode, the researchers developed a process to infiltrate a solid polymer electrolyte into the prefabricated iron fluoride electrode. They then hot pressed the entire structure to increase density and reduce any voids.

Stretchy plastic electrolytes could enable new lithium-ion battery design

Gleb Yushin, a professor in Georgia Tech’s School of Materials Science and Engineering and Kostiantyn Turcheniuk, research scientist in Yushin’s lab, inspect a battery using a new cathode design that replaces expensive metals and traditional liquid electrolyte with lower cost transition metal fluorides and a solid polymer electrolyte. Credit: Allison Carter

Two central features of the polymer-based electrolyte are its ability to flex and accommodate the swelling of the iron fluoride while cycling and its ability to form a very stable and flexible interphase with iron fluoride. Traditionally, that swelling and massive side reactions have been key problems with using iron fluoride in previous battery designs.

“Cathodes made from iron fluoride have enormous potential because of their high capacity, low material costs and very broad availability of ,” Yushin said. “But the volume changes during cycling as well as parasitic side reactions with liquid electrolytes and other degradation issues have limited their use previously. Using a solid electrolyte with elastic properties solves many of these problems.”

The researchers then tested several variations of the new solid-state batteries to analyze their performance over more than 300 cycles of charging and discharging at elevated temperature of 122 degrees Fahrenheit, noting that they outperformed previous designs using metal  even when these were kept cool at room temperatures.

The researchers found that the key to the enhanced battery performance was the solid polymer electrolyte. In previous attempts to use metal fluorides, it was believed that metallic ions migrated to the surface of the cathode and eventually dissolved into the liquid electrolyte, causing a capacity loss, particularly at elevated temperatures. In addition,  fluorides catalyzed massive decomposition of liquid electrolytes when cells were operating above 100 degrees Fahrenheit. However, at the connection between the solid electrolyte and the cathode, such dissolving doesn’t take place and the solid electrolyte remains remarkably stable, preventing such degradations, the researchers wrote.

“The polymer electrolyte we used was very common, but many other solid electrolytes and other battery or electrode architectures—such as core-shell particle morphologies—should be able to similarly dramatically mitigate or even fully prevent parasitic side reactions and attain stable performance characteristics,” said Kostiantyn Turcheniuk, research scientist in Yushin’s lab and a co-author of the manuscript.

In the future, the researchers aim to develop new and improved solid electrolytes to enable fast charging and also to combine solid and liquid electrolytes in new designs that are fully compatible with conventional cell manufacturing technologies employed in large battery factories.


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Nanoparticles used to Transport Anti-Cancer Agent to Cells – University of Cambridge


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Cells with MOFs carrying siRNA. Credit: University of Cambridge

Scientists from the University of Cambridge have developed a platform that uses nanoparticles known as metal-organic frameworks to deliver a promising anti-cancer agent to cells.

Research led by Dr. David Fairen-Jimenez, from the Cambridge Department of Chemical Engineering and Biotechnology, indicates  (MOFs) could present a viable platform for delivering a potent anti-cancer agent, known as siRNA, to .

Small interfering ribonucleic acid (siRNA), has the potential to inhibit overexpressed cancer-causing genes, and has become an increasing focus for scientists on the hunt for new cancer treatments.

Fairen-Jimenez’s group used computational simulations to find a MOF with the perfect pore size to carry an siRNA molecule, and that would breakdown once inside a cell, releasing the siRNA to its target. Their results were published today in Cell Press journal, Chem.

Some cancers can occur when  inside cells cause over-production of particular proteins. One way to tackle this is to block the gene expression pathway, limiting the production of these proteins.

SiRNA molecules can do just that—binding to specific gene messenger molecules and destroying them before they can tell the cell to produce a particular protein. This process is known as ‘gene knockdown’. Scientists have begun to focus more on siRNAs as potential cancer therapies in the last decade, as they offer a versatile solution to disease treatment—all you need to know is the sequence of the gene you want to inhibit and you can make the corresponding siRNA that will break it down. Instead of designing, synthesising and testing new drugs—an incredibly costly and lengthy process—you can make a few simple changes to the siRNA molecule and treat an entirely different disease.

One of the problems with using siRNAs to treat disease is that the molecules are very unstable and are often broken down by the cell’s natural defence mechanisms before they can reach their targets. SiRNA molecules can be modified to make them more stable, but this compromises their ability to knock down the target genes. It’s also difficult to get the molecules into cells—they need to be transported by another vehicle acting as a delivery agent.

Nanoparticles used to transport anti-cancer agent to cells
Crystalline metal-organic framework. Credit: David Fairen-Jimenez

The Cambridge researchers have used a special nanoparticle to protect and deliver siRNA to cells, where they show its ability to inhibit a specific target gene.

Fairen-Jimenez leads research into advanced materials, with a particular focus on MOFs: self-assembling 3-D compounds made of metallic and organic building blocks connected together.

There are thousands of different types of MOFs that researchers can make—there are currently more than 84,000 MOF structures in the Cambridge Structural Database with 1000 new structures published each month—and their properties can be tuned for specific purposes. By changing different components of the MOF structure, researchers can create MOFs with different pore sizes, stabilities and toxicities, enabling them to design structures that can carry molecules such as siRNAs into cells without harmful side effects.

“With traditional cancer therapy if you’re designing new drugs to treat the system, these can have different behaviours, geometries, sizes, and so you’d need a MOF that is optimal for each of these individual drugs,” says Fairen-Jimenez. “But for siRNA, once you develop one MOF that is useful, you can in principle use this for a range of different siRNA sequences, treating different diseases.”

“People that have done this before have used MOFs that don’t have a porosity that’s big enough to encapsulate the siRNA, so a lot of it is likely just stuck on the outside,” says Michelle Teplensky, former Ph.D. student in Fairen-Jimenez’s group, who carried out the research. “We used a MOF that could encapsulate the siRNA and when it’s encapsulated you offer more protection. The MOF we chose is made of a zirconium based metal node and we’ve done a lot of studies that show zirconium is quite inert and it doesn’t cause any toxicity issues.”

Using a biodegradable MOF for siRNA delivery is important to avoid unwanted build-up of the structures once they’ve done their job. The MOF that Teplensky and team selected breaks down into harmless components that are easily recycled by the cell without harmful side effects. The large pore size also means the team can load a significant amount of siRNA into a single MOF molecule, keeping the dosage needed to knock down the genes very low.

“One of the benefits of using a MOF with such large pores is that we can get a much more localised, higher dose than other systems would require,” says Teplensky. “SiRNA is very powerful, you don’t need a huge amount of it to get good functionality. The dose needed is less than 5% of the porosity of the MOF.”Structure-and-mechanism-of-siRNA-A-Structure-of-siRNA-B-Action-of-RNAi

MOFs or other vehicles to carry small molecules into cells is that they are often stopped by the cells on the way to their target. This process is known as endosomal entrapment and is essentially a defence mechanism against unwanted components entering the cell. Fairen-Jimenez’s team added extra components to their MOF to stop them being trapped on their way into the cell, and with this, could ensure the siRNA reached its target.

The team used their system to knock down a gene that produces fluorescent proteins in the cell, so they were able to use microscopy imaging methods to measure how the fluorescence emitted by the proteins compared between cells not treated with the MOF and those that were. The group made use of in-house expertise, collaborating with super-resolution microscopy specialists Professors Clemens Kaminski and Gabi Kaminski-Schierle, who also lead research in the Department of Chemical Engineering and Biotechnology.

Using the MOF platform, the team were consistently able to prevent gene expression by 27%, a level that shows promise for using the technique to knock down cancer genes.

Fairen-Jimenez believes they will be able to increase the efficacy of the system and the next steps will be to apply the platform to genes involved in causing so-called hard-to-treat cancers.

“One of the questions we get asked a lot is ‘why do you want to use a metal-organic framework for healthcare?’, because there are metals involved that might sound harmful to the body,” says Fairen-Jimenez. “But we focus on difficult diseases such as hard-to-treat cancers for which there has been no improvement in treatment in the last 20 years. We need to have something that can offer a solution; just extra years of life will be very welcome.”

The versatility of the system will enable the team to use the same adapted MOF to deliver different siRNA sequences and target different . Because of its large pore size, the MOF also has the potential to deliver multiple drugs at once, opening up the option of combination therapy.


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Automated Electric Shuttle Makes its Debut on NREL Campus


NREL Auto EV CaMPUES 20190910-autonomous-vehicle-celebration

The EasyMile automated electric shuttle took its inaugural ride around the NREL campus this week.

NREL’s intelligent campus ventures accelerated this week with the introduction of an automated electric vehicle in its employee shuttle fleet.

Designed to cover short distances and predefined routes, the fully electric EasyMile EZ10 shuttle took its inaugural ride on Monday, transporting staff and visitors around NREL’s South Table Mountain campus after a dedication ceremony marking its first day of operation.

Attending the dedication were NREL Director Martin Keller, Associate Laboratory Directors Johney Green and Julie Baker, and shuttle partners Jeff Womack of MV Transportation and Sharad Agarwal of EasyMile. The event drew local press from The Denver Post, CBS4, and the Golden Transcript, who interviewed Green as well as Kevin Walkowicz, manager of NREL’s Advanced Vehicles and Fueling Infrastructure Group, and Jeffrey Gonder, manager of NREL’s Mobility, Behavior, and Advanced Powertrains Group.

The automated vehicle serves as one of two circulator shuttles primarily transporting staff to and from the parking garage during peak hours. For the first year, onboard vehicle stewards from MV Transportation, the lab’s shuttle service subcontractor, will monitor vehicle operations to ensure safety.

The shuttle can carry up to 12 passengers and is designed to travel along a pre-programmed route. It is equipped with a full range of sensors and an intelligent vehicle system to detect obstacles and avoid collisions. Real-time data processing allows the driverless vehicle system to decide how to behave as it progresses safely along the road.

In-Use Operations Data to Inform Research Efforts

NREL will collect and analyze vehicle and charging system operational data to help researchers better understand associated energy use, charging and energy storage needs, and autonomous systems operation and control.

“The results of our data analysis effort will help inform the design and optimization of intelligent energy management systems onboard these types of vehicles—such as managed wireless charging or predictive route-based propulsion system control,” said Walkowicz.

NREL will also explore ways in which these systems can enable intelligent load management for the entire campus in scenarios with a high concentration of energy coming from renewables or behind-the-meter energy storage.

“It will also feed into NREL’s mobility modeling and energy impacts analyses of connected and automated vehicles, in particular related to automated mobility districts—campus-sized implementations of connected and automated vehicle technologies geared to realize the benefits of a fully electric automated mobility service within a confined region or district,” said Gonder.

Ultimately, this research effort will provide insight into a variety of areas important to the connected, intelligent, and automated vehicle space including grid integration, intelligent charge management, energy use, urban mobility, and human interactions with automated transportation systems.

Learn more about NREL’s transportation research and its on-campus sustainability efforts.

 

Researchers the University of Pennsylvania Think ‘Small’ to make Progress Towards Better Fuel Cells


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Graduate student Jennifer Lee uses a large transmission electron microscope, housed in the Singh Center, to take a closer look at the nanomaterials and nanocrystals that are synthesized in the lab. Credit: University of Pennsylvania

As renewable sources such as wind and solar are quickly changing the energy landscape, scientists are looking for ways to better store energy for when it’s needed. Fuel cells, which convert chemical energy into electrical power, are one possible solution for long-term energy storage, and could someday be used to power trucks and cars without burning fuel. But before fuel cells can be widely used, chemists and engineers need to find ways to make this technology more cost-effective and stable.

A new study from the lab of Penn Integrates Knowledge Professor Christopher Murray, led by graduate student Jennifer Lee, shows how custom-designed nanomaterials can be used to address these challenges. In ACS Applied Materials & Interfaces, researchers show how a  can be built from cheaper, more widely available metals using an atomic-level design that also gives the material long-term stability. Former post-doc Davit Jishkariani and former students Yingrui Zhao and Stan Najmr, current student Daniel Rosen, and professors James Kikkawa and Eric Stach, also contributed to this work.

The chemical reaction that powers a fuel cell relies on two electrodes, a negative anode and a positive cathode, separated by an electrolyte, a substance that allows the ions to move. When fuel enters the anode, a catalyst separates molecules into protons and electrons, with the latter traveling toward the cathode and creating an electric current.

Catalysts are typically made of precious metals, like platinum, but because the chemical reactions only occur on the surface of the material, any atoms that are not presented on the surface of the material are wasted. It’s also important for catalysts to be stable for months and years because fuel  are very difficult to replace.

Researchers think small to make progress towards better fuel cells
When not busy at the microscope or analyzing data, researchers in the Murray group work on synthesizing new nanomaterials. Credit: University of Pennsylvania

Chemists can address these two problems by designing custom nanomaterials that have platinum at the surface while using more common metals, such as cobalt, in the bulk to provide stability. The Murray group excels at creating well-controlled nanomaterials, known as nanocrystals, in which they can control the size, shape, and composition of any composite nanomaterial.

In this study, Lee focused on the catalyst in the cathode of a specific type of fuel cell known as a proton exchange membrane fuel cell. “The cathode is more of a problem, because the materials are either platinum or platinum-based, which are expensive and have slower reaction rates,” she says. “Designing the catalyst for the cathode is the main focus of designing a good fuel cell.”

The challenge, explains Jishkariani, was in creating a cathode in which platinum and cobalt atoms would form into a stable structure. “We know cobalt and platinum mixes well; however, if you make alloys of these two, you have added atoms of platinum and cobalt in a random order,” he says. Adding more cobalt in a random order causes it to leach out into the electrode, meaning that the fuel cell will only function for a short time.

To solve this problem, researchers designed a catalyst made of layered platinum and cobalt known as an intermetallic phase. By controlling exactly where each atom sat in the catalyst and locking the structure in place, the cathode catalyst was able to work for longer periods than when the atoms were arranged randomly. As an additional unexpected finding, the researchers found that adding more cobalt to the system led to greater efficiency, with a 1-to-1 ratio of platinum to cobalt, better than many other structures with a wide range of platinum-to-cobalt ratios.

Researchers think small to make progress towards better fuel cells
The Xeuss 2.0 X-ray scattering instrument, which came to the LRSM in 2018, helps researchers characterize the structures of a wide range of hard and soft materials.  Credit: University of Pennsylvania

The next step will be to test and evaluate the intermetallic material in fuel cell assemblies to make direct comparisons to commercially-available systems. The Murray group will also be working on new ways to create the intermetallic structure without high temperatures and seeing if adding additional atoms improve the catalyst’s performance.

This work required high-resolution microscopic imaging, work that Lee previously did at Brookhaven National Lab but, thanks to recent acquisitions, can now be done at Penn in the Singh Center for Nanotechnology. “Many of the high-end experiments that we would have had to travel to around the country, sometimes around the world, we can now do much closer to home,” says Murray. “The advances that we’ve brought in electron microscopy and X-ray scattering are a fantastic addition for people that work on energy conversion and catalytic studies.”

Lee also experienced first-hand how chemistry research directly connects to real world challenges. She recently presented this work at the International Precious Metals Institute conference and says that meeting members of the precious-metals community was enlightening. “There are companies looking at fuel cell technology and talking about the newest design of the fuel cell cars,” she says. “You get to interact with people that think of your project from different perspectives.”

Murray sees this fundamental research as a starting point towards commercial implementation and real world application, emphasizing that future progress relies on the forward-looking research that’s happening now. “Thinking about a world where we’ve displaced a lot of the traditional fossil -based inputs, if we can figure out this interconversion of electrical and , that will address a couple of very important problems simultaneously.”


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Precious Metal Flecks Could be Catalyst for Better Cancer Therapies


Precious Metal Flecks Cancer shutterstock_716719006

 

Researchers have found a way to dispatch minute fragments of palladium—a key component in motor manufacture, electronics and the oil industry—inside cancerous cells.

Tiny extracts of a precious metal used widely in industry could play a vital role in new cancer therapies.

Scientists have long known that the metal, used in catalytic converters to detoxify exhaust, could be used to aid cancer treatment but, until now, have been unable to deliver it to affected areas.

A molecular shuttle system that targets specific cancer cells has been created by a team at the University of Edinburgh and the Universidad de Zaragoza in Spain.

The new method, which exploits palladium’s ability to accelerate—or catalyse—chemical reactions, mimics the process some viruses use to cross cell membranes and spread infection.

The team has used bubble-like pouches that resemble the biological carriers known as exosomes, which can transport essential proteins and genetic material between cells. These exosomes exit and enter cells, dump their content, and influence how the cells behave.

This targeted transport system, which is also exploited by some viruses to spread infection to other cells and tissues, inspired the team to investigate their use as shuttles of therapeutics.

The researchers have now shown that this complex communication network can be hijacked. The team created exosomes derived from lung cancer cells and cells associated with glioma—a tumour that occurs in the brain and spinal cord—and loaded them with palladium catalysts.

These artificial exosomes act as Trojan horses, taking the catalysts—which work in tandem with an existing cancer drug- straight to primary tumours and metastatic cells.

Having proved the concept in laboratory tests, the researchers have now been granted a patent that gives them exclusive rights to trial palladium-based therapies in medicine.

The study was funded by the Engineering and Physical Sciences Research Council and the European Research Council. It has been published in the journal, Nature Catalysis.

Professor Asier Unciti-Broceta, from the University of Edinburgh’s CRUK Edinburgh Centre, said: “We have tricked exosomes naturally released by cancer cells into taking up a metal that will activate chemotherapy drugs just inside the cancer cells, which could leave healthy cells untouched.”

Professor Jesús Santamaría, of the Universidad de Zaragoza, said: “This has the potential to be a very exciting technology. It could allow us to target the main tumour and metastatic cells, thus reducing the side effects of chemotherapy without compromising the treatment.”

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Materials provided by University of Edinburgh. Note: Content may be edited for style and length.

Flexible Solar Cells a Step Closer to Reality … Lower Cost and Improved Performance – University of Warwick


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Solar cells that use mixtures of organic molecules to absorb sunlight and convert it to electricity, that can be applied to curved surfaces such as the body of a car, could be a step closer thanks to a discovery that challenges conventional thinking about one of the key components of these devices.

A basic organic solar cell consists of a thin film of organic semiconductors sandwiched between two electrodes which extract charges generated in the organic semiconductor layer to the external circuit. It has long been assumed that 100% of the surface of each electrode should be electrically conductive to maximise the efficiency of charge extraction.

Scientists at the University of Warwick have discovered that the electrodes in organic solar cells actually only need ~1% of their surface area to be electrically conductive to be fully effective, which opens the door to using a range of composite materials at the interface between the electrodes and the light harvesting organic semiconductor layers to improve device performance and reduce cost. The discovery, published today (11 September), is reported in Advanced Functional Materials.

The academic lead, Dr Ross Hatton from the University’s Department of Chemistry, said: “It’s widely assumed that if you want to optimise the performance of organic solar cells you need to maximize the area of the interface between the electrodes and the organic semiconductors. We asked whether that was really true.”

The researchers developed a model electrode that they could systematically change the surface area of, and found that when as much as 99% of its surface was electrically insulating the electrode still performs as well as if 100% of the surface was conducting, provided the conducting regions aren’t too far apart.Nanotechnology-in-Solar-Energy-2

High performance organic solar cells have additional transparent layers at the interfaces between the electrodes and the light harvesting organic semiconductor layer that are essential for optimising the light distribution in the device and improving its stability, but must also be able to conduct charges to the electrodes. This is a tall order and not many materials meet all of these requirements.

Dr Dinesha Dabera, the post-doctoral researcher on this Leverhulme Trust funded project, explains:“This new finding means composites of insulators and conducting nano-particles such as carbon nanotubes, graphene fragments or metal nanoparticles, could have great potential for this purpose, offering enhanced device performance or lower cost.

“Organic solar cells are very close to being commercialised but they’re not quite there yet, so anything that allows you to further reduce cost whilst also improving performance is going to help enable that.”

Dr Hatton, who was interviewed by Serena Bashal of the UK Youth Climate Coalition at the British Science Festival this week, explains: “What we’ve done is to demonstrate a design rule for this type of solar cell, which opens up much greater possibilities for materials choice in the device and so could help to enable their realisation commercially.’’

Organic solar cells are potentially very environmentally friendly, because they contain no toxic elements and can be processed at low temperature using roll-to-roll deposition, so can have an extremely low carbon footprint and a short energy payback time.

Dr Hatton explains: “There is a fast growing need for solar cells that can be supported on flexible substrates that are lightweight and colour-tuneable. Conventional silicon solar cells are fantastic for large scale electricity generation in solar farms and on the roofs of buildings, but they are poorly matched to the needs of electric vehicles and for integration into windows on buildings, which are no longer niche applications. Organic solar cells can sit on curved surfaces, and are very lightweight and low profile.

“This discovery may help enable these new types of flexible solar cells to become a commercial reality sooner because it will give the designers of this class of solar cells more choice in the materials they can use.”

From Nano Magazine.com

Tesla battery experts describe million-mile cell in new paper


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At the Tesla Autonomy Event in April, Elon Musk said the Disruptors of Detroit were working on a new battery pack that would last a cool million miles, and said it would be available next year. Now Tesla battery research partner Jeff Dahn and his team have released a paper in which they describe this million-mile battery cell.

The new Li-ion battery cell features a next-generation “single crystal” NMC cathode and a new type of electrolyte. Dahn’s team has extensively tested the cells, and believe they could enable a battery pack that lasts over a million miles in an EV.

The team’s paper, A Wide Range of Testing Results on an Excellent Lithium-Ion Cell Chemistry to be used as Benchmarks for New Battery Technologies, was published in the Journal of The Electrochemical Society. The following brief excerpt (via Electrek) describes the results of testing the new cells:

“Up to three years of testing has been completed for some of the tests. Tests include long-term charge-discharge cycling at 20, 40 and 55° C, long-term storage at 20, 40 and 55° C, and high precision coulometry at 40° C. Several different electrolytes are considered in this LiNi0.5Mn0.3Co0.2O2/graphite chemistry, including those that can promote fast charging. The reasons for cell performance degradation and impedance growth are examined using several methods. We conclude that cells of this type should be able to power an electric vehicle for over 1.6 million kilometers (1 million miles) and last at least two decades in grid energy storage.”

This is a huge advance – the new cells last two to three times longer than Tesla’s current cells – and if the company can bring the new technology into production in a reasonable timeframe, it could radically change the economics of EVs.

The paper notes the importance of long-lasting batteries for such vehicles as robotaxis, long-haul trucks and transit buses. In these applications, a battery’s ability to deliver a high number of charge/discharge cycles is critical, in contrast to the consumer vehicle market, in which maximum range is the most important feature (at least from a marketing standpoint).

The paper also mentions vehicle-to-grid applications, which could someday allow EV owners to earn revenue from their cars while they aren’t being driven (see the upcoming issue of Charged for a profile of Fermata Energy, a pioneer in this space).

Meanwhile, job listings on Tesla’s web site seem to confirm rumors that the company plans to start manufacturing its own battery cells (as reported by Electrek).

The possibilities are endless.

Long-term cycling data plotted as percent initial capacity versus equivalent full cycles for NMC/graphite cells as described in the legend. The data from this work for 100% DOD cycling was collected to an upper cutoff potential of 4.3 V. The data from Ecker et al.,2 used 4.2 V as 100% state of charge. The purple and green data (this work) should be compared to the black data (Ecker et al.). Data for restricted range cycling (i.e. 25 – 75% SOC and 40 -60% SOC) for the cells in this work is not available but is expected to be far better than the data shown for 0 – 100% DOD cycling by analogy with the cells tested by Ecker et al.
Capacity remaining versus storage time for NMC/graphite cells as determined by reference performance testing every several months. The data from Ecker et al.2 and Schmitt et al.6 are for Sanyo UR18650E and Sony US18650V3 cells, respectively. The voltages and temperatures at which the cells were stored are given in the legends.
a) Measured properties of the NMC532/graphite 402035 (40 mm x 20 mm x 3.5 mm thick) pouch cells used here. The positive electrode was 94% active material, the loading was 21.1 mg/cm2 (target was 21.3) and the electrode density was 3.5 g/cm3. The negative electrode was 95.4% active material, the loading was 12.2 mg/cm2 (target was 11.8) and the electrode density was 1.55 g/cm3. b) Stack energy density of the NMC532/graphite couple for several electrode thicknesses. b) Stack energy density calculations – gives values for the electrode stack (negative coating/copper/negative coating/separator/positive coating/aluminum/positive coating/separator). Assumptions – copper foil = 8 μm, aluminum foil = 15 μm, separator = 16 μm, N/P capacity ratio = 1.1 at 4.3 V, average cell voltage = 3.75 V. The highlighted row represents the design used in this work.

Source: Journal of The Electrochemical Society