Graphene Oxide: Introduction and Market News - Page 27

A team of researchers at Brown University developed a composite catalyst using nitrogen-rich graphene dotted with copper nanoparticles. It was shown in a study that the new catalyst is able to efficiently and selectively convert carbon dioxide to ethylene, one of the world's most important commodity chemicals that is used to make plastics, construction materials and other products.

Chemical companies produce ethylene by the millions of tons each year using processes that usually involve fossil fuels. If excess carbon dioxide can indeed be used to make ethylene, like the results of this study imply, it could help make the chemical industry become more sustainable and eco-friendly. There is, however, much more work to be done before bringing such a process to an industrial scale.

A research team at Los Alamos, along with collaborators from Oak Ridge National Laboratory, the University of New Mexico, and Rutgers University, has developed a new water-removal technique that improves the performance of carbon nanomaterials used in fuel cells and batteries. The study may present new avenues for designing advanced carbon nanomaterials for batteries and fuel cells.

The study gives an in-depth understanding of the role water plays in graphene oxide nanosheets or functionalized graphene sheets. Dry films of graphene oxide include a significant volume of added water that builds up between the oxygen-functionalized nanosheets and is also usually produced in aqueous solutions. The researchers showed how a simple solvent drying method can remove the accumulated water between the graphitic sheets. When water is removed, the physical structure of these graphene oxide nanosheets changes considerably, and the distance between the nanosheets is also reduced. In addition to this, the researchers also noted that the concentration of functional groups changed significantly, resulting in highly ordered structures. These changes ultimately led to improved electrocatalytic activity, which substantially improves the performance in batteries and fuel cells.

Researchers at Brown University have demonstrated that graphene, wrinkled and crumpled in a multi-step process, becomes significantly better at repelling water - a property that could be useful in making self-cleaning surfaces. Crumpled graphene also has enhanced electrochemical properties, which could make it more useful as electrodes in batteries and fuel cells.

The researchers aimed to build relatively complex architectures incorporating both wrinkles and crumples. To do that, the researchers deposited layers of graphene oxide onto shrink films -polymer membranes that shrink when heated. As the films shrink, the graphene on top is compressed, causing it to wrinkle and crumple. To see what kind of structures they could create, the researchers compressed same graphene sheets multiple times. After the first shrink, the film was dissolved away, and the graphene was placed in a new film to be shrunk again.

Researchers from the US and Australia used graphene oxide to design a filter that allows water and other liquids to be filtered nine times faster than the current leading commercial filter, by developing a viscous form of graphene oxide that could be spread very thinly with a blade.

The researchers explain that this technique creates a uniform arrangement in the graphene, and that evenness gives the filter special properties; The filter can capture viruses and bacteria - in fact, anything larger than one nanometer cannot get through the graphene layer.

Researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a battery-like hydrogen fuel cell, which surrounds hydrogen-absorbing magnesium nanocrystals with graphene oxide sheets to improve its performance.

The graphene shields the nanocrystals from oxygen, moisture and contaminants, while tiny, natural holes allow the smaller hydrogen molecules to pass through. This filtering process overcomes common problems degrading the performance of metal hydrids for hydrogen storage. The graphene-encapsulated magnesium crystals act as "sponges" for hydrogen, offering a very compact and safe way to take in and store hydrogen. The nanocrystals also permit faster fueling, and reduce the overall size.

Researchers at the Catholic University of the Sacred Heart and the Institute for Complex Systems in Rome studied how the size and concentration of graphene-oxide sheets affects its antimicrobial capabilities. They found that GO was extremely effective against bacteria, even in low concentrations and sizes, which could mean that it can be used as a coating material for medical instruments and devices to reduce infections, as well as reducing antibiotic use and antibiotic resistance.

The team examined the effect of GO on three bacteria: Staphylococcus aureus and Enterococcus faecalis, both of which cause various opportunistic and hospital-acquired infections, and Escherichia coli, which can cause severe food poisoning. They found that 200 nm sheets of graphene oxide in a water solution killed around 90% of S. aureus and E. faecalis, and around 50% of E. coli in less than two hours. Graphene oxide was effective against bacteria, even at concentrations below 10 μg/ml.

Researchers at Kansas State University, University of Buffalo and the State University of New York have designed a new technique for 3D printing graphene aerogels with complex microstructures. The technique combines drop-on-demand 3D printing with freeze casting.

Aerogels are light and spongy materials that can be used as both thermal and optical insulators and can potentially be used as batteries and catalysts within electronic components. Recent years have brought about methods in which aerogels can be produced with certain 3D printers. The scientists have now developed a new 3D printing technique for producing graphene aerogels, which they hope will open up new uses for the material.

Scientists at Lawrence Livermore National Laboratory and UC Santa Cruz have demonstrated what might be the world's first 3D-printed graphene composite aerogel supercapacitor, using a technique known as direct-ink writing. The researchers suggest that their ultra-lightweight graphene aerogel supercapacitors may open the door to novel designs of highly efficient energy storage systems for smartphones, wearables, implantable devices, electric cars and wireless sensors.

The key factor in developing these novel aerogels is creating an extrudable graphene oxide-based composite ink and modifying the 3D printing method to accommodate aerogel processing. The 3D-printed graphene composite aerogel (3D-GCA) electrodes are lightweight, highly conductive, and exhibit excellent electrochemical properties. Supercapacitors using these 3D-GCA electrodes with thicknesses on the order of millimeters display exceptional capacitive retention (ca. 90% from 0.5 to 10 A·g−1) and power densities (>4 kW·kg−1).

Researchers at the University of California at Berkeley and the Lawrence Berkeley National Laboratory have developed a new solution-based, cost-effective way to wrap reduced graphene oxide around the surface of ultrathin transparent conducting copper nanowires. The technique aims to significantly improve the stability of the wires in air and reduce the amount of light scattered by the materials.

Thin films made of the wires might be used in optoelectronics devices, particularly in displays and flexible electronics. Metal nanowire films could make good replacements for the expensive and brittle indium tin oxide (ITO) in next-generation electronics, thanks to their excellent electrical and optical properties and the fact that they can be easily processed in solution.

Researchers at the Barcelona Institute of Science and Technology have managed to print graphene oxide onto different materials, including paper, and use it as a touch sensitive electronic device. They transferred graphene oxide coated on a wax printed membrane to paper, an adhesive film and even a t-shirt by simply using pressure and water, and also printed graphene oxide onto plastic and, as the oxide conducts electricity, used it as a touch sensitive LED switch.