Rice University - Page 5

Rice University scientists have attached ruthenium atoms to graphene to create a durable catalyst for high-performance fuel cells. Most catalysts used to drive the oxygen reduction reaction that lets fuel cells turn chemical energy into electricity are made of platinum, which stands up to the acidic nature of the cell’s charge-carrying electrolyte. However, platinum is expensive, and replacements have long been searched for by researchers.

The ruthenium-graphene combination may pose a suitable replacement; In tests, its performance was said to easily match that of traditional platinum-based alloys and bested iron and nitrogen-doped graphene, another contender.

Researchers at Rice University and China's Tianjin University have used 3D laser printing to fabricate centimeter-sized graphene objects. The team has demonstrated the making of graphene foams from non-graphene starting materials, in a method that could reportedly be scaled for additive manufacturing applications with pore-size control. The process is conducted at room temperature, without the need for molds. The rather unusual starting materials are powdered sugar and nickel powder.

3D laser printers work differently than the more familiar extrusion-based 3D printers, which create objects by squeezing melted plastic through a needle as they trace out two-dimensional patterns. In 3D laser sintering, a laser shines down onto a flat bed of powder. Wherever the laser touches powder, it melts or sinters the powder into a solid form. The laser is rastered, or moved back and forth, line by line to create a single two-dimensional slice of a larger object. Then a new layer of powder is laid over the top of that layer and the process is repeated to build up three-dimensional objects from successive two-dimensional layers.

Researchers at Rice University and Ben-Gurion University of the Negev in Israel (BGU) have shown that laser-induced graphene LIG (that was invented at Rice) is a highly effective anti-fouling and anti-biofouling material (that protects surfaces from the buildup of microorganisms, plants or other biological material on wet surfaces), and, when electrified, also serves as a bacteria zapper.

This form of graphene is extremely resistant to biofilm formation, which has promise for places like water-treatment plants, oil-drilling operations, hospitals and ocean applications like underwater pipes that are sensitive to fouling, Prof. James Tour says. The antibacterial qualities when electricity is applied is a great additional benefit.

Researchers at Rice University have created a rechargeable Li-ion battery, based on a hybrid of graphene and carbon nanotubes, with three times the capacity of commercial lithium-ion batteries. This was achieved mainly by addressing a major challenge known as the dendrite problem.

The Rice battery stores lithium in a unique anode made of a seamless hybrid of graphene and carbon nanotubes. The material (first created at Rice in 2012) is basically a 3D carbon surface that provides abundant area for lithium to occupy. The anode itself is said to approach the theoretical maximum for storage of lithium metal with its 3,351 milliamp hours per gram capacity, while resisting the formation of damaging dendrites or "mossy" deposits.

Researchers at Rice University, who invented laser-induced graphene (LIG), in collaboration with researchers at Ben-Gurion University in Israel, have designed a way to make the spongy graphene either superhydrophobic or superhydrophilic.

Until recently, the Rice lab made LIG in open air only, using a laser to burn part of the way through a flexible polyimide sheet to get interconnected flakes of graphene. However, putting the polymer in a closed environment with various gases changed the product’s properties. Forming LIG in argon or hydrogen makes it superhydrophobic (extremely water-avoiding), a property highly beneficial for separating water from oil or de-icing surfaces. Forming it in oxygen or air makes it superhydrophilic (extremely water-attracting), making it highly soluble.

Prof. James Tour's research lab in Rice University is one of the leading graphene research groups in the world, with several key technologies first discovered and developed there. Professor Tour is involved with several application areas - from de-icing coating to energy storage and quantum dots production. Prof. Tour was kind enough to share his time and update us on the latest research and commercialization efforts at his lab.

The Tour group is now commercializing two of its key technologies. First up is the laser-induced graphene (or LiG), which was reported first in 2014. This is a process in which graphene is formed on a flexible polyimide film using a room-temperature laser-based process. It is possible to pattern this graphene to create devices and as it is formed on a flexible film this easily enables flexible electronics applications.

Researchers from Rice University, led by the renowned Prof. James M. Tour, are attempting to repair spinal cord injuries with the help of TexasPEG, a water soluble graphene nanoribbon dispersion. In rodents, the method has been able to restore a completely paralyzed rat to a motility score of 19 out of 21, where 21 is a perfect score. If successful in humans as well, it may be applicable to new injuries, and potentially old injuries up to 30 years in the past - restoring function and sensation in both paraplegics and quadriplegics.

The team's novel approach acts as a directional scaffold for the neurons to grow along. It uses highly conductive graphene nanoribbons (GNR), which are long and thin. These graphene nanoribbons have been chemically modified to be water soluble (PEG-GNR), so they can disperse well between the existing neurons. Neurons then attach to these GNRs, and grow axons and dendrites along them until they re-connect with another neuron. These PEG-GNR are dissolved in PEG600 to form a solution that is topically administered to cuts in the spinal cord. This solution has been named TexasPEG by researchers in the field.

Researchers at Rice University have constructed a graphene foam, reinforced by carbon nanotubes, that can support more than 3,000 times its own weight and bounce back to its original height. In addition, its shape and size are easily controlled - which the team demonstrated by creating a screw-shaped piece of the material.

The 3D structures were created from a powdered nickel catalyst, surfactant-wrapped multiwall nanotubes and sugar as a carbon source. The materials were mixed and the water evaporated; the resulting pellets were pressed into a steel die and then heated in a chemical vapor deposition furnace, which turned the available carbon into graphene. After further processing to remove remnants of nickel, the result was an all-carbon foam in the shape of the die, in this case a screw. The team said the method will be easy to scale up.

Researchers at Rice University have found that it may be possible to make graphene-carbon nanotube junctions excel at transferring heat, turning these into an attractive way to channel damaging heat away from next-generation nano-electronics. This could, in theory, be done by putting a cone-like chimney between the graphene and nanotube to eliminate the barrier that blocks heat from escaping.

Graphene and carbon nanotubes both excel at the rapid transfer of electricity and phonons, but when a nanotube grows from graphene, atoms facilitate the turn by forming heptagonal (seven-member) rings instead of the usual six-atom rings. Scientists have determined that forests of nanotubes grown from graphene are excellent for storing hydrogen for energy applications, but in electronics, the heptagons scatter phonons and hinder the escape of heat through the pillars.

Researchers at Rice University have found that nitrogen-doped graphene quantum dots (NGQDs) could be an efficient electrocatalyst for making complex hydrocarbons from carbon dioxide, and used electrocatalysis to demonstrated the conversion of the greenhouse gas into small batches of ethylene and ethanol. This could prove a fascinating and simple way to recycle waste carbon dioxide into valuable fuel.

While the researchers say that the exact mechanism is yet to be fully explored, they found that NGQDs worked nearly as efficiently as copper, which is also being tested as a catalyst to reduce carbon dioxide into liquid fuels and chemicals. In lab tests, NGQDs proved able to reduce carbon dioxide by up to 90% and convert 45% into either ethylene or alcohol, comparable to copper electrocatalysts. NGQDs also have the advantage of keeping their catalytic activity for a long time.