Hydrogen made from seawater

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University of Houston Texas Center for Superconductivity Director, Zhifeng Ren. Image credit: University of Houston. 

A new catalyst has enabled hydrogen to be made from seawater. 

University of Houston, USA, researchers found combining an oxygen and a hydrogen evolution reaction catalyst together achieved current densities capable of supporting industrial demands while requiring relatively low voltage to start seawater electrolysis.

The researchers said the device, made with non-noble metal nitrides, avoids obstacles that have made it difficult to make hydrogen or safe drinking water from seawater. 

University of Houston Texas Center for Superconductivity Director, Zhifeng Ren, said a major issue had been that there wasn’t a catalyst that could split seawater to produce hydrogen without also setting free ions of sodium, chlorine, calcium and other components of seawater, which once freed can settle on the catalyst and render it inactive. Chlorine ions are especially challenging, in part because chlorine requires only a slightly higher voltage to free than is needed to free hydrogen.

The researchers designed and synthesised a 3D core-shell oxygen evolution reaction catalyst using transition metal-nitride, with nanoparticles made of a nickle-iron-nitride compound and nickle-molybdenum-nitride nanorods on porous nickle foam.

University of Houston Postdoctoral Researcher and first paper author, Luo Yu, said the new oxygen evolution reaction catalyst was paired with a hydrogen one of nickle-molybdenum-nitride nanorods.

The catalysts were integrated into a two-electrode alkaline electrolyser, which can be powered by waste heat via a thermoelectric device or by an AA battery.

Cell voltages required to produce a current density of 100 milliamperes per square centimetre (a measure of current density, or mA cm-2) ranged from 1.564V to 1.581V.

The voltage is significant, Yu said, because while a voltage of at least 1.23V is required to produce hydrogen, chlorine is produced at a voltage of 1.73V, meaning the device had to be able to produce meaningful levels of current density with a voltage between the two levels.

The researchers tested the catalysts with seawater drawn from Galveston Bay, off the Texas coast. Ren said it also would work with wastewater.

The work is described in Nature Communications.

The future of chips: SMART announces success…

The future of chips: SMART announces successful way to manufacture novel integrated silicon III-V chips

The Singapore-MIT Alliance for Research and Technology (SMART), MIT’s Research Enterprise in Singapore, has announced the successful development of a commercially viable way to manufacture integrated Silicon III-V Chips with high-performance III-V devices inserted into their design.

In most devices today, silicon-based CMOS chips are used for computing, but they are not efficient for illumination and communications, resulting in low efficiency and heat generation. This is why current 5G mobile devices on the market get very hot upon use and would shut down after a short time.

This is where III-V semiconductors are valuable. III-V chips are made from elements in the 3rd and 5th columns of the elemental periodic table such as Gallium Nitride (GaN) and Indium Gallium Arsenide (InGaAs). Due to their unique properties, they are exceptionally well suited for optoelectronics (LEDs) and communications (5G etc) – boosting efficiency substantially.

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2D Materials: Dicalcium nitride

2D Materials: Dicalcium nitride

An electride material, dicalcium nitride (Ca2N) is a compound in which an electron functions as the anion. Because dicalcium nitride is a layered material, it can be considered to be a 2D electride with the formula [Ca2N]+e

This material has a hexagonal crystal structure and forms a shiny green plate like crystal in the bulk. As with graphene, mechanical exfoliation can be used to separate the layers. Similar materials, such as those with strontium in the place of calcium, have also been shown to exist. However, these such materials are still relatively unknown and used for almost exclusively for research (electrides themselves are considered to be a fairly recent discovery, first synthesized in the early 1980s). 

Sources/Further Reading: ( 1 – image 1 ) ( 2 ) ( 3

You’re not so tough, h-BN: Rice Universi…

You’re not so tough, h-BN: Rice University chemists find new path to make strong 2D material better for applications

Two-dimensional h-BN, an insulating material also known as “white graphene,” is four times stiffer than steel and an excellent conductor of heat, a benefit for composites that rely on it to enhance their properties.

Those qualities also make h-BN hard to modify. Its tight hexagonal lattice of alternating boron and nitrogen atoms is highly resistant to change, unlike graphene and other 2D materials that can be easily modified — aka functionalized — with other elements.

The Rice lab of chemist Angel Martí has published a protocol to enhance h-BN with carbon chains. These turn the 2D tough guy into a material that retains its strength but is more amenable to bonding with polymers or other materials in composites.

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A graphene superconductor that plays more than…

A graphene superconductor that plays more than one tune: Researchers at Berkeley Lab have developed a tiny toolkit for scientists to study exotic quantum physics

Researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a graphene device that’s thinner than a human hair but has a depth of special traits. It easily switches from a superconducting material that conducts electricity without losing any energy, to an insulator that resists the flow of electric current, and back again to a superconductor – all with a simple flip of a switch. Their findings were reported today in the journal Nature.

[…]

“Usually, when someone wants to study how electrons interact with each other in a superconducting quantum phase versus an insulating phase, they would need to look at different materials. With our system, you can study both the superconductivity phase and the insulating phase in one place,” said Guorui Chen, the study’s lead author and a postdoctoral researcher in the lab of Feng Wang, who led the study. Wang, a faculty scientist in Berkeley Lab’s Materials Sciences Division, is also a UC Berkeley physics professor.

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Ceramics: Silicon oxynitride

Ceramics: Silicon oxynitride

While silicon oxynitride is technically defined as those ceramics with the general composition of SiOxNy (in the amorphous form, this means anything from SiO2 to Si3N4), the most well known form of this material has the chemical formula of Si2N2O. This is the only known intermediary crystalline phase, and can be found in small amounts in nature as the mineral sinoite, the crystal structure of which can be shown above. 

Most practical applications of this ceramic utilizes amorphous thin films of the material. The range of structures listed above allows for a range of properties that can be tuned based on the exact composition of the oxynitride in question (for example, SiO2 has a refractive index of 1.45, while Si3N4 has a refractive index of 2, which allows for a variety of waveguides to be constructed). 

The crystalline structure (Si2N2O), meanwhile, is known to be an excellent refractory material, with high chemical and oxidation resistance. Finally, these ceramics are occasionally doped with metal atoms, such as aluminum as a ceramic known as sialon, or lanthanides to produce phosphors. 

Sources/Further Reading: ( 1 ) ( 2 ) ( 3 – image 3 ) ( 4 ) ( 5 )

Image sources: ( 1 ) ( 2 )

Curbing the flammability of epoxy resin

Curbing the flammability of epoxy resin

In a paper to be published in a forthcoming issue of Nano, a team of researchers from Henan University have investigated the flame retardant performance of epoxy resin using a boron nitride nanosheet decorated with cobalt ferrite nanoparticles.

Polymers are widely used in our daily lives due to good physical and chemical stability, corrosion resistance and other superior properties. However, most polymers, due to their organic nature, are inherently flammable which is a potential threat to the safety of human life and property. In order to avoid or reduce the flammability of polymers, it is a good strategy to add flame retardants to the polymers.

Among them, two-dimensional (2-D) layered inorganic nanomateirals (nanosheets), represented by graphene oxide, molybdenum disulfide, and boron nitride nanosheets (BNNS), exhibit excellent flame retardant performance due to their good physical barrier effects. However, the flame retardance is not enough in the use of such 2-D inorganic flame retardants alone, and in particular, the ability to suppress toxic gases and smoke is weak.

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Regular

Organic electronics: a new semiconductor in the carbon-nitride family

Teams from Humboldt-Universität and the Helmholtz-Zentrum Berlin have explored a new material in the carbon-nitride family. Triazine-based graphitic carbon nitride (TGCN) is a semiconductor that should be highly suitable for applications in optoelectronics. Its structure is two-dimensional and reminiscent of graphene. Unlike graphene, however, the conductivity in the direction perpendicular to its 2D planes is 65 times higher than along the planes themselves.

Some organic materials might be able to be utilised similarly to silicon semiconductors in optoelectronics. Whether in solar cells, light-emitting diodes, or in transistors – what is important is the band gap, i.e. the difference in energy level between electrons in the valence band (bound state) and the conduction band (mobile state). Charge carriers can be raised from the valence band into the conduction band by means of light or an electrical voltage. This is the principle behind how all electronic components operate. Band gaps of one to two electron volts are ideal.

A team headed by chemist Dr. Michael J. Bojdys at Humboldt University Berlin recently synthesised a new organic semiconductor material in the carbon-nitride family. Triazine-based graphitic carbon nitride (or TGCN) consists of only carbon and nitrogen atoms, and can be grown as a brown film on a quartz substrate.The combination of C and N atoms form hexagonal honeycombs similar to graphene, which consists of pure carbon.Just as with graphene, the crystalline structure of TGCN is two-dimensional.With graphene, however, the planar conductivity is excellent, while its perpendicular conductivity is very poor. In TGCN it is exactly the opposite: the perpendicular conductivity is about 65 times greater than the planar conductivity. With a band gap of 1.7 electron volts, TGCN is a good candidate for applications in optoelectronics.

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New way to beat the heat in electronics: Rice …

New way to beat the heat in electronics: Rice University lab’s flexible insulator offers high strength and superior thermal conduction

A nanocomposite invented at Rice University’s Brown School of Engineering promises to be a superior high-temperature dielectric material for flexible electronics, energy storage and electric devices. A lab video shows how quickly heat disperses from a composite of a polymer nanoscale fiber layer and boron nitride nanosheets. When exposed to light, both materials heat up, but the plain polymer nanofiber layer on the left retains the heat far longer than the composite at right.

[…]

The nanocomposite combines one-dimensional polymer nanofibers and two-dimensional boron nitride nanosheets. The nanofibers reinforce the self-assembling material while the “white graphene” nanosheets provide a thermally conductive network that allows it to withstand the heat that breaks down common dielectrics, the polarized insulators in batteries and other devices that separate positive and negative electrodes.

The discovery by the lab of Rice materials scientist Pulickel Ajayan is detailed in Advanced Functional Materials.

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Photodoping in 2-D materials for fabrication…

Photodoping in 2-D materials for fabrication of logic devices

National University of Singapore scientists have discovered a method for photoinduced electron doping on molybdenum ditelluride (MoTe2) heterostructures for fabricating next generation logic devices.

Two-dimensional (2-D) transition metal dichalcogenides (TMDs) are promising building blocks for the development of next generation electronic devices. These materials are atomically thin and exhibit unique electrical properties. Researchers are interested to develop n- and p-type field effect transistors (FET) using the 2-D TMDs for building fundamental logic circuit components. These components include p-n junctions and inverters.

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