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.


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.

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.


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.


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.


“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.



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.


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.


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.”


New Cheap Catalyst To Produce Hydrogen From Water

Graphene doped with nitrogen and augmented with cobalt atoms has proven to be an effective, durable catalyst for the production of hydrogen from water, according to scientists at Rice University. The Rice lab of chemist James Tour and colleagues at the Chinese Academy of Sciences, the University of Texas at San Antonio and the University of Houston have reported the development of a robust, solid-state catalyst that shows promise to replace expensive platinum for hydrogen generation.

Tucson fuel cell

Catalysts can split water into its constituent hydrogen and oxygen atoms, a process required for fuel cells. Hydrogen electric cars as the Tucson from Hyundai are powered by fuel cells.
The latest discovery, detailed in Nature Communications, is a significant step toward lower-cost catalysts for energy production, according to the researchers.

What’s unique about this paper is that we show not the use of metal particles, not the use of metal nanoparticles, but the use of atoms,” Tour said. “The particles doing this chemistry are as small as you can possibly get.
We’re getting away with very little cobalt to make a catalyst that nearly matches the best platinum catalysts.” In comparison tests, he said the new material nearly matched platinum’s efficiency to begin reacting at a low onset voltage, the amount of electricity it needs to begin separating water into hydrogen and oxygen.


Electric Power: How To Increase Solar Cells Efficiency

Rice University researchers have demonstrated an efficient new way to capture the energy from sunlight and convert it into clean, renewable energy by splitting water molecules.

Hot elsplitting water Riceectrons have the potential to drive very useful chemical reactions, but they decay very rapidly, and people have struggled to harness their energy,” said lead researcher Isabell Thomann, assistant professor of nanoengineering at Rice. “For example, most of the energy losses in today’s best photovoltaic solar panels are the result of hot electrons that cool within a few trillionths of a second and release their energy as wasted heat.” Capturing these high-energy electrons before they cool could allow solar-energy providers to significantly increase their solar-to-electric power-conversion efficiencies  and reduce  the cost of solar electricity.

In the light-activated nanoparticles studied by Thomann and colleagues at Rice’s Laboratory for Nanophotonics (LANP), light is captured and converted into plasmons, waves of electrons that flow like a fluid across the metal surface of the nanoparticles. Plasmons are high-energy states that are short-lived, but researchers at Rice and elsewhere have found ways to capture plasmonic energy and convert it into useful heat or light. Plasmonic nanoparticles also offer one of the most promising means of harnessing the power of hot electrons, and LANP researchers have made progress toward that goal in several recent studies.

Thomann and her team created a system that uses the energy from hot electrons to split molecules of water into oxygen and hydrogen. That’s important because oxygen and hydrogen are the feedstocks for fuel cells, electrochemical devices that produce electricity cleanly and efficiently.

Because of the inherent inefficiencies, we wanted to find a new approach to the problem,” Thomann said. “We took an unconventional approach: Rather than driving off the hot electrons, we designed a system to carry away the electron holes. In effect, our setup acts like a sieve or a membrane. The holes can pass through, but the hot electrons cannot, so they are left available on the surface of the plasmonic nanoparticles.”

The technology, is described online in the American Chemical Society journal Nano Letters.



EV: A Thin Film That Produces Oxygen and Hydrogen

A cobalt-based thin film serves double duty as a new catalyst that produces both hydrogen and oxygen from water to feed fuel cells, according to scientists at Rice University. This discovery may lower the cost of future hydrogen electric car.  The inexpensive, highly porous material invented by the Rice lab of chemist James Tour may have advantages as a catalyst for the production of hydrogen via water electrolysis. A single film far thinner than a hair can be used as both the anode and cathode in an electrolysis device.

The researchers led by Rice postdoctoral researcher Yang Yang reported their discovery  in Advanced Materials.

They determined their cobalt film is much better at producing hydrogen than most state-of-the-art materials and is competitive with (and much cheaper than) commercial platinum catalysts. They reported the catalyst also produced an oxygen evolution reaction comparable to current materials.


A side view of a porous cobalt phosphide/phosphate thin film created at Rice University. The robust film could replace expensive metals like platinum in water-electrolysis devices that produce hydrogen and oxygen for fuel cells. The scale bar equals 500 nanometers.

It is amazing that in water-splitting, the same material can make both hydrogen and oxygen,” Tour said. “Usually materials make one or the other, but not both.”

The researchers suggested applying alternating current from wind or solar energy sources to cobalt-based electrolysis could be an environmentally friendly source of hydrogen and oxygen.


New Cheap Catalyst For Hydrogen Electric Car

Graphene nanoribbons formed into a three-dimensional aerogel and enhanced with boron and nitrogen are excellent catalysts for fuel cells, used in hydrogen electric car, even in comparison to platinum, according to Rice University researchers. The reactions in most current fuel cells are catalyzed by platinum, but platinum’s high cost has prompted the search for alternative. A team led by materials scientist Pulickel Ajayan and chemist James Tour made metal-free aerogels from graphene nanoribbons and various levels of boron and nitrogen to test their electrochemical properties. In tests involving half of the catalytic reaction that takes place in fuel cells, they discovered versions with about 10 percent boron and nitrogen were efficient in catalyzing what’s known as an oxygen reduction reaction, a step in producing energy from feedstocks like methanol.
Ajayan’s Rice lab has excelled in turning nanostructures into macroscopic materials, like the oil-absorbing sponges invented in 2012 or, more recently, solid nanotube blocks with controllable densities and porosities.

hydrogen-electric car
The key to developing carbon-based catalysts is in the doping process, especially with elements such as nitrogen and boron,” he said. “The graphitic carbon-boron-nitrogen systems have thrown many surprises in recent years, especially as a viable alternative to platinum-based catalysts.”. The Rice process is unique, he said, because it not only exposes the edges but also provides porous conduits that allow reactants to permeate the material.
The research appeared in the American Chemical Society journal Chemistry of Materials.


Graphene: Extraordinary Potential As Body Armour

Graphene’s great strength appears to be determined by how well it stretches before it breaks, according to Rice University scientists who tested the material’s properties by peppering it with microbullets.
The two-dimensional carbon honeycomb discovered a decade ago is thought to be much stronger than steel. But the Rice lab of materials scientist Edwin “Ned” Thomas didn’t need even close to a pound of graphene to prove the material is on average 10 times better than steel at dissipating kinetic energy.
While other labs have looked extensively at graphene’s electronic properties and tensile strength, nobody had taken comprehensive measurements of its ability to absorb an impact, Thomas said. His lab found graphene’s ability to simultaneously be stiff, strong and elastic gives it extraordinary potential for use as body armor or for shielding spacecraft.
In 2012, they first used an earlier version of LIPIT to determine the properties of multiblock copolymers that could not only stop microbullets but also completely encase them. In every case, the 3.7-micron spheres punctured the graphene. But rather than a neat hole, the spheres left a fractured pattern of “petals” around the point of impact, indicating the graphene stretched before breaking.

bullet against graphene
We started writing about the petals, but as we went along, it became evident that wasn’t really the story,” said Thomas, the William and Stephanie Sick Dean of Rice’s George R. Brown School of Engineering. “The bullet’s kinetic energy interacts with the graphene, pushes forward, stretches the film and is slowed down.”

The researchers report in the latest edition of Science that firing microscopic projectiles at multilayer sheets of graphene allowed the scientists to determine just how hard it is to penetrate at the nano level – and how strong graphene could be in macroscopic applications.