Cheap, Robust Catalyst Splits Water Into Hydrogen And Oxygen

Splitting water into hydrogen and oxygen to produce clean energy can be simplified with a single catalyst developed by scientists at Rice University and the University of Houston. The electrolytic film produced at Rice and tested at Houston is a three-layer structure of nickel, graphene and a compound of iron, manganese and phosphorus. The foamy nickel gives the film a large surface, the conductive graphene protects the nickel from degrading and the metal phosphide carries out the reactionRice chemist Kenton Whitmire and Houston electrical and computer engineer Jiming Bao and their labs developed the film to overcome barriers that usually make a catalyst good for producing either oxygen or hydrogen, but not both simultaneously.

A catalyst developed by Rice University and the University of Houston splits water into hydrogen and oxygen without the need for expensive metals like platinum. This electron microscope image shows nickel foam coated with graphene and then the catalytic surface of iron, manganese and phosphorus

Regular metals sometimes oxidize during catalysis,” Whitmire said. “Normally, a hydrogen evolution reaction is done in acid and an oxygen evolution reaction is done in base. We have one material that is stable whether it’s in an acidic or basic solution.

The discovery builds upon the researchers’ creation of a simple oxygen-evolution catalyst revealed earlier this year. In that work, the team grew a catalyst directly on a semiconducting nanorod array that turned sunlight into energy for solar water splittingElectrocatalysis requires two catalysts, a cathode and an anode. When placed in water and charged, hydrogen will form at one electrode and oxygen at the other, and these gases are captured. But the process generally requires costly metals to operate as efficiently as the Rice team’s catalyst.

The standard for hydrogen evolution is platinum,” Whitmire explained. “We’re using Earth-abundant materials — iron, manganese and phosphorus — as opposed to noble metals that are much more expensive.

The robust material is the subject of a paper in Nano Energy.

Source: http://news.rice.edu/

Solar Nanotechnology-based Desalination

A new desalination system has been developed that combines membrane distillation technology and light-harvesting nanophotonics. Called nanophotonics-enabled solar membrane distillation technology, or NESMD for short, the development has come from the Center for Nanotechnology Enabled Water Treatment (NEWT), based at Rice University. The system works whereby hot salt water is flowed across one side of a porous membrane and cold freshwater is flowed across the otherWater vapor is naturally drawn through the membrane from the hot to the cold side, and because the seawater doesn’t need to be boiled, the energy requirements are less than they would be for traditional distillation, according to the researchers. However, the energy costs are still significant because heat is continuously lost from the hot side of the membrane to the cold.

Unlike traditional membrane distillation, NESMD benefits from increasing efficiency with scale,” said Rice’s Naomi Halas, a corresponding author on the paper and the leader of NEWT‘s  nanophotonics research efforts. “It requires minimal pumping energy for optimal distillate conversion, and there are a number of ways we can further optimise the technology to make it more productive and efficient.

The distillation membrane in the chamber contained a specially designed top layer of carbon black nanoparticles infused into a porous polymer. The light-capturing nanoparticles heated the entire surface of the membrane when exposed to sunlight. A thin half-millimeter-thick layer of salt water flowed atop the carbon-black layer, and a cool freshwater stream flowed below.

Rice scientist and water treatment expert Qilin Li said the water production rate increased greatly by concentrating the sunlight: “The intensity got up 17.5 kilowatts per meter squared when a lens was used to concentrate sunlight by 25 times, and the water production increased to about 6 liters per meter squared per hour.”

In the PNAS study, researchers offered proof-of-concept results based on tests with an NESMD chamber about the size of three postage stamps and just a few millimeters thick.

Source: http://www.waterworld.com/

3-D Printed Graphene Foam

Nanotechnologists from Rice University and China’s Tianjin University have used 3-D laser printing to fabricate centimeter-sized objects of atomically thin graphene. The research could yield industrially useful quantities of bulk graphene and is described online in a new study in the American Chemical Society journal ACS Nano.

Laser sintering was used to 3-D print objects made of graphene foam, a 3-D version of atomically thin graphene. At left is a photo of a fingertip-sized cube of graphene foam; at right is a close-up of the material as seen with a scanning electron microscope

This study is a first of its kind,” said Rice chemist James Tour, co-corresponding author of the paper. “We have shown how to make 3-D graphene foams from nongraphene starting materials, and the method lends itself to being scaled to graphene foams for additive manufacturing applications with pore-size control.”

Graphene, one of the most intensely studied nanomaterials of the decade, is a two-dimensional sheet of pure carbon that is both ultrastrong and conductive. Scientists hope to use graphene for everything from nanoelectronics and aircraft de-icers to batteries and bone implants. But most industrial applications would require bulk quantities of graphene in a three-dimensional form, and scientists have struggled to find simple ways of creating bulk 3-D graphene.

For example, researchers in Tour’s lab began using lasers, powdered sugar and nickel to make 3-D graphene foam in late 2016. Earlier this year they showed that they could reinforce the foam with carbon nanotubes, which produced a material they dubbed “rebar graphene” that could retain its shape while supporting 3,000 times its own weight. But making rebar graphene was no simple task. It required a pre-fabricated 3-D mold, a 1,000-degree Celsius chemical vapor deposition (CVD) process and nearly three hours of heating and cooling.  “This simple and efficient method does away with the need for both cold-press molds and high-temperature CVD treatment,” said co-lead author Junwei Sha, a former student in Tour’s lab who is now a postdoctoral researcher at Tianjin. “We should also be able to use this process to produce specific types of graphene foam like 3-D printed rebar graphene as well as both nitrogen- and sulfur-doped graphene foam by changing the precursor powders.” Sha and colleagues conducted an exhaustive study to find the optimal amount of time and laser power to maximize graphene production. The foam created by the process is a low-density, 3-D form of graphene with large pores that account for more than 99 percent of its volume.

The 3-D graphene foams prepared by our method show promise for applications that require rapid prototyping and manufacturing of 3-D carbon materials, including energy storage, damping and sound absorption,” said co-lead author Yilun Li, a graduate student at Rice.

Source: http://news.rice.edu/

Solar Energy Transforms Salt Water Into Fresh Drinking Water

A federally funded research effort to revolutionize water treatment has yielded an off-grid technology that uses energy from sunlight alone to turn salt water into fresh drinking water. The desalination system, which uses a combination of membrane distillation technology and light-harvesting nanophotonics, is the first major innovation from the Center for Nanotechnology Enabled Water Treatment (NEWT), a multi-institutional engineering research center based at Rice University.

NEWT’s “nanophotonics-enabled solar membrane distillation” technology, or NESMD, combines tried-and-true water treatment methods with cutting-edge nanotechnology that converts sunlight to heat. More than 18,000 desalination plants operate in 150 countries, but NEWT’s desalination technology is unlike any other used today.

Direct solar desalination could be a game changer for some of the estimated 1 billion people who lack access to clean drinking water,” said Rice scientist and water treatment expert Qilin Li, a corresponding author on the study. “This off-grid technology is capable of providing sufficient clean water for family use in a compact footprint, and it can be scaled up to provide water for larger communities.”

The technology is described online in the Proceedings of the National Academy of Sciences.

Source: http://news.rice.edu/

Rechargeable Lithium Metal Battery

Rice University scientists have created a rechargeable lithium metal battery with three times the capacity of commercial lithium-ion batteries by resolving something that has long stumped researchers: the dendrite problem.

The Rice battery stores lithium in a unique anode, a seamless hybrid of graphene and carbon nanotubes. The material first created at Rice in 2012 is essentially a three-dimensional carbon surface that provides abundant area for lithium to inhabit. Lithium metal coats the hybrid graphene and carbon nanotube anode in a battery created at Rice University. The lithium metal coats the three-dimensional structure of the anode and avoids forming dendrites.

The anode itself approaches the theoretical maximum for storage of lithium metal while resisting the formation of damaging dendrites or “mossy” deposits.

Dendrites have bedeviled attempts to replace lithium-ion with advanced lithium metal batteries that last longer and charge faster. Dendrites are lithium deposits that grow into the battery’s electrolyte. If they bridge the anode and cathode and create a short circuit, the battery may fail, catch fire or even explode.

Rice researchers led by chemist James Tour found that when the new batteries are charged, lithium metal evenly coats the highly conductive carbon hybrid in which nanotubes are covalently bonded to the graphene surface. As reported in the American Chemical Society journal ACS Nano, the hybrid replaces graphite anodes in common lithium-ion batteries that trade capacity for safety.

Lithium-ion batteries have changed the world, no doubt,” Tour said, “but they’re about as good as they’re going to get. Your cellphone’s battery won’t last any longer until new technology comes along.

He said the new anode’s nanotube forest, with its low density and high surface area, has plenty of space for lithium particles to slip in and out as the battery charges and discharges. The lithium is evenly distributed, spreading out the current carried by ions in the electrolyte and suppressing the growth of dendrites.

Source: http://news.rice.edu

Clean Renewable Source Of Hydrogen Fuel For Electric Car

Rice University scientists have created an efficient, simple-to-manufacture oxygen-evolution catalyst that pairs well with semiconductors for solar water splitting, the conversion of solar energy to chemical energy in the form of hydrogen and oxygen.

anode RiceA photo shows an array of titanium dioxide nanorods with an even coating of an iron, manganese and phosphorus catalyst. The combination developed by scientists at Rice University and the University of Houston is a highly efficient photoanode for artificial photosynthesis. Click on the image for a larger version

The lab of Kenton Whitmire, a Rice professor of chemistry, teamed up with researchers at the University of Houston and discovered that growing a layer of an active catalyst directly on the surface of a light-absorbing nanorod array produced an artificial photosynthesis material that could split water at the full theoretical potential of the light-absorbing semiconductor with sunlight. An oxygen-evolution  catalyst splits water into hydrogen and oxygen. Finding a clean renewable source of hydrogen fuel is the focus of extensive research, but the technology has not yet been commercialized.

The Rice team came up with a way to combine three of the most abundant metalsiron, manganese and phosphorus — into a precursor that can be deposited directly onto any substrate without damaging it. To demonstrate the material, the lab placed the precursor into its custom chemical vapor deposition (CVD) furnace and used it to coat an array of light-absorbing, semiconducting titanium dioxide nanorods. The combined material, called a photoanode, showed excellent stability while reaching a current density of 10 milliamps per square centimeter, the researchers reported.

The results appear in two new studies. The first, on the creation of the films, appears in Chemistry: A European Journal. The second, which details the creation of photoanodes, appears in ACS Nano.

Source: http://news.rice.edu/

How To Track Stem Cells In The Body

Rice University researchers have synthesized a new and greatly improved generation of contrast agents for tagging and real-time tracking of stem cells in the body. The agent combines ultrashort carbon nanotubes and bismuth clusters that show up on X-rays taken with computed tomography (CT) scanners. The stable compound performs more than eight times better than the first-generation material introduced in 2013, according to the researchers.

XRAY
An improved compound of bismuth and carbon nanotubes called Bi4C@US-tubes, developed at Rice University could enhance the ability to track stem cells as they move through the body and target diseases

The primary application will be to track them in stem-cell therapies to see if the cells are attracted to the site of disease — for example, cancer — and in what concentration,” said Rice chemist Lon Wilson of the compound the researchers call Bi4C@US-tubes.

Magnetic resonance imaging is currently used for that purpose and it works quite well, but X-ray technology in the clinic is much more available,” he said. “It’s faster and cheaper, and it could facilitate preclinical studies to track stem cells in vivo.”

Bismuth is used in cosmetics, pigments and pharmaceuticals, notably as the active ingredient in pink bismuth (aka Pepto-Bismol), an antacid. For this application, bismuth nanoclusters developed by the lab of Rice chemist Kenton Whitmire, a co-author of the paper, are combined with carbon nanotubes chemically treated to shorten them to between 20 and 80 nanometers and add defects to their side walls. The nanoclusters, which make up about 20 percent of the compound, appear to strongly attach to the nanotubes via these defects.

When introduced into stem cells, the treated nanotubes become easy to spot, Wilson said. “It’s very interesting to see a cell culture that is opaque to X-rays. They’re not as dark as bone (which X-rays cannot penetrate), but they’re really dark when they’re loaded with these agents.”

The process developed by Wilson’s team and colleagues at CHI St. Luke’s Health-Baylor St. Luke’s Medical Center and Baylor College of Medicine is detailed this month in the American Chemical Society journal ACS Applied Materials and Interfaces.

Source: http://news.rice.edu/

How To Store Hydrogen Fuel In Electric Cars

Layers of graphene separated by nanotube pillars of boron nitride may be a suitable material to store hydrogen fuel in cars, according to Rice University scientists. The Department of Energy has set benchmarks for storage materials that would make hydrogen a practical fuel for light-duty vehicles. The Rice lab of materials scientist Rouzbeh Shahsavari determined in a new computational study that pillared boron nitride and graphene could be a candidate.

hydrogenSimulations by Rice scientists show that pillared graphene boron nitride may be a suitable storage medium for hydrogen-powered vehicles. Above, the pink (boron) and blue (nitrogen) pillars serve as spacers for carbon graphene sheets (grey). The researchers showed the material worked best when doped with oxygen atoms (red), which enhanced its ability to adsorb and desorb hydrogen (white).

 

Just as pillars in a building make space between floors for people, pillars in boron nitride graphene make space for hydrogen atoms. The challenge is to make them enter and stay in sufficient numbers and exit upon demand.Shahsavari’s lab had already determined through computer models how tough and resilient pillared graphene structures would be, and later worked boron nitride nanotubes into the mix to model a unique three-dimensional architecture. (Samples of boron nitride nanotubes seamlessly bonded to graphene have been made.)

In their latest molecular dynamics simulations, the researchers found that either pillared graphene or pillared boron nitride graphene would offer abundant surface area (about 2,547 square meters per gram) with good recyclable properties under ambient conditions. Their models showed adding oxygen or lithium to the materials would make them even better at binding hydrogen. They focused the simulations on four variants: pillared structures of boron nitride or pillared boron nitride graphene doped with either oxygen or lithium. At room temperature and in ambient pressure, oxygen-doped boron nitride graphene proved the best, holding 11.6 percent of its weight in hydrogen (its gravimetric capacity) and about 60 grams per liter (its volumetric capacity); it easily beat competing technologies like porous boron nitride, metal oxide frameworks and carbon nanotubes.

The study by Shahsavari and Farzaneh Shayeganfar appears in the American Chemical Society journal Langmuir.

Source: http://news.rice.edu/

Tatoo Therapy

A temporary tattoo to help control a chronic disease might someday be possible, according to scientists at Baylor College of Medicine who tested antioxidant nanoparticles created at Rice University. A proof-of-principle study led by Baylor scientist Christine Beeton published by Nature’s online, open-access journal Scientific Reports shows that nanoparticles modified with polyethylene glycol are conveniently choosy as they are taken up by cells in the immune system. That could be a plus for patients with autoimmune diseases like multiple sclerosis, one focus of study at the Beeton lab.

tatoo-therapy

“Placed just under the skin, the carbon-based particles form a dark spot that fades over about one week as they are slowly released into the circulation,” Beeton said. T and B lymphocyte cells and macrophages are key components of the immune system. However, in many autoimmune diseases such as multiple sclerosis, T cells are the key players. One suspected cause is that T cells lose their ability to distinguish between invaders and healthy tissue and attack both.

In tests at Baylor, nanoparticles were internalized by T cells, which inhibited their function, but ignored by macrophages. “The ability to selectively inhibit one type of cell over others in the same environment may help doctors gain more control over autoimmune diseases,” Beeton said. “The majority of current treatments are general, broad-spectrum immunosuppressants,” said Redwan Huq, lead author of the study and a graduate student in the Beeton lab. “They’re going to affect all of these cells, but patients are exposed to side effects (ranging) from infections to increased chances of developing cancer. So we get excited when we see something new that could potentially enable selectivity.” Since the macrophages and other splenic immune cells are unaffected, most of a patient’s existing immune system remains intact, he added.

 

Source: http://news.rice.edu/

How To Triple Perovskite Solar Cells Efficiency

A new type of two-dimensional-layered perovskite developed by Northwestern University, Los Alamos National Laboratory and Rice University researchers will open up new horizons for next-generation stable solar-cell devices and new opto-electronic devices such as light-emitting diodes, lasers and sensors.

The research team has tweaked its crystal production method and developed a 2-D perovskite with outstanding stability and more than triple the material’s previous power conversion efficiency. This could bring perovskite crystals closer to use in the burgeoning solar power industry.

flipping crystals

  • Crystal orientation has been a puzzle for more than two decades, and this is the first time we’ve been able to flip the crystal in the actual casting process,” said Hsinhan Tsai, a Rice graduate student at Los Alamos working with senior researcher and study lead co-author Aditya Mohite.

This is our breakthrough, using our spin-casting technique to create layered crystals whose electrons flow vertically down the material without being blocked, mid layer, by organic cations,” Tsai said.

Northwestern scientists created the two-dimensional material used by the researchers at Los Alamos in the new solar cells. Mercouri G. Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences, and Costas Stoumpos, a postdoctoral fellow in Kanatzidis’ group, had been exploring an interesting 2-D material that orients its layers perpendicular to the substrate.

This breakthrough resulted from a very strong synergy between our institutions — the materials design team at Northwestern that designed and prepared high-quality samples of the materials and showed they are promising and the Los Alamos team’s excellent skills in making solar cells and optimizing them to high performance,” Kanatzidis said.

Wanyi Nie, a Los Alamos co-author on the paper, noted, “The new 2-D perovskite is both more efficient and more stable, both under constant lighting and in exposure to the air, than the existing 3-D organic-inorganic crystals.

The study was published July 6 by the journal Nature.

Source: http://www.lanl.gov/

Red Light To Attack Viruses

Light is helping Rice University scientists control both the infectivity of viruses and gene delivery to the nuclei of target cells. The researchers have developed a method to use two shades of red to control the level and spatial distribution of gene expression in cells via an engineered virus.

Although viruses have evolved to deliver genes into host cells, they still face difficulties getting their payloads from the cytoplasm into a cell’s nucleus, where gene expression occurs. The Rice labs of bioengineers Junghae Suh and Jeffrey Tabor have successfully found a way to overcome this critical hurdle. The result from labs at Rice’s BioScience Research Collaborative combines Suh’s interest in designing viruses to deliver genes to target cells with Tabor’s skills in optogenetics, in which light-responsive proteins can be used to control biological behavior. They built custom adeno-associated virus (AAV) vectors by incorporating proteins that naturally come together when exposed to red light (650-nanometer wavelengths) and break apart when exposed to far red (750-nanometer wavelengths). These naturally light-responsive proteins help the viral capsids – the hard shells that contain genetic payloadsenter the host cell nuclei.

red light against virusesViruses in general are relatively efficient at delivering genes into cells, but they still experience great limiting barriers,” she said. “If you add these viruses to cells, most of them seem to hang out outside of the nucleus, and only a small fraction make their way inside, which is the goal,” said Junghae Suh.

The team drew upon the Tabor lab’s expertise in optogenetics to increase the AAVs’ efficiency. “Jeff works with many different types of light-responsive proteins. The particular pair we decided upon was first identified in plants. Light is really nice because you can apply it externally and you can control many aspects: at what areas the light is exposed, the duration of exposure, the intensity of the light and, of course, its wavelength,” she added.

Source: http://news.rice.edu/

Nanoscale Submarines Will Carry Cargoes Through The Blood

Though they’re not quite ready for boarding a lá “Fantastic Voyage,” nanoscale submarines created at Rice University are proving themselves seaworthy. Each of the single-molecule, 244-atom submersibles built in the Rice lab of chemist James Tour has a motor powered by ultraviolet light. With each full revolution, the motor’s tail-like propeller moves the sub forward 18 nanometers.

And with the motors running at more than a million RPM, that translates into speed. Though the sub’s top speed amounts to less than 1 inch per second, Tour said that’s a breakneck pace on the molecular scale.

submarine at nanoscale

These are the fastest-moving molecules ever seen in solution,” he said.

Expressed in a different way, the researchers reported this month in the American Chemical Society journal Nano Letters that their light-driven nanosubmersibles show an “enhancement in diffusion” of 26 percent. That means the subs diffuse, or spread out, much faster than they already do due to Brownian motion, the random way particles spread in a solution. While they can’t be steered yet, the study proves molecular motors are powerful enough to drive the sub-10-nanometer subs through solutions of moving molecules of about the same size.

This is akin to a person walking across a basketball court with 1,000 people throwing basketballs at him,” Tour said. Rice’s researchers hope future nanosubs will be able to carry cargoes for medical and other purposes. “There’s a path forward,” García-López said. “This is the first step, and we’ve proven the concept. Now we need to explore opportunities and potential applications.”

Source: http://news.rice.edu/