Scientists at University of California, Berkeley have developed a new catalyst that can help generate hydrogen from water.
Their catalyst is made up of nanometre-thin layers of metal carbide that creates a self-assembly process that utilises gelatine. Metal ions such as molybdenum, tungsten or cobalt are added to water and gelatine and then left to dry.
“We believe that as gelatine dries, it self-assembles layer by layer,” said Professor of Mechanical Engineering at UC Berkeley and senior author Liwei Lin. “The metal ion is carried by the gelatine, so when the gelatine self-assembles, your metal ion is also arranged into these flat layers.”
When heated to 600°C, the metal ions react with the carbon atoms, forming thin sheets as the gelatine is burnt away.
By placing the catalysts in water and running an electric current through them, they were able to split the water more efficiently than running a current through the water alone. The researchers found that the most efficient formula was to combine the molybdenum carbide with a small amount of cobalt.
The thin sheets help maximise the catalysts surface area, making them highly efficient for their weight.
Currently, the best water-splitting catalyst available is platinum, a relatively rare and very expensive material.
“We found that the performance is very close to the best catalyst made of platinum and carbon, which is the gold standard in this area,” Lin said. “This means that we can replace the very expensive platinum with our material, which is made in a very scalable manufacturing process.”
Speaking of platinum, do not yet count out its role in hydrogen production. A team from Argonne National Laboratory in the US has also developed a new catalyst, one that maximises the effectiveness of platinum.
Their catalyst needs only around a quarter of the platinum used in current technology.
First, the scientists altered the shape of the platinum in order to maximise its reactivity by covering a cobalt-platinum nanoparticle core with a few thin layers of pure platinum.
“To use a platinum-cobalt core-shell alloy allows us to make larger number of catalytically active particles to spread over the catalyst surface, but this is only the first step,” said Argonne chemist Di-Jia Liu.
In order to handle the large influx of oxygen, the Argonne scientists supported the cobalt-platinum nanoparticles with a catalytically active, cobalt-nitrogen-carbon composite substrate.
These catalytically active centres were uniformly placed close to the platinum-cobalt particles and are capable of assisting in the break-down of the oxygen bonds in the water molecules to produce hydrogen.
The end result used less valuable platinum, but was also more efficient and durable compared to either component on its own.
“Since the new catalysts require only an ultralow amount of platinum, similar to that used in existing automobile catalytic converters, it could help to ease the transition from conventional internal combustion engines to fuel cell vehicles without disrupting the platinum supply chain and market,” Liu said.
Researchers at Osaka University have a flexible thermoelectric generator (FlexTEG) module. The device is comprised of a densely packed thermoelectric semiconductor chips mounted on a flexible substrate.
The module is able to convert waste heat energy into electrical energy.
The flexibility helps make the device more efficient, as waste heat can be more effectively recovered from a curved surface. The design also makes it more reliable, as less mechanical stress is exerted on the modules’ semiconductor chips.
The device mounts its top electrodes in parallel, which provides it with its enhanced flexibility. Traditional thermoelectric conversion modules mount their electrodes perpendicularly on two sides, making them unable to bend in any direction.
“Because of heat resistance of all semiconductor packaging materials (up to around 150°C) and mechanical flexibility of the module, our FlexTEG module will be used as a conversion thermoelectric generator module for waste heat of 150°C or lower. Its mounting technique is based on conventional semiconductor packaging techniques, so mass production and cost reduction of thermoelectric conversion modules are anticipated,” said lead author Tohru Sugahara.
A new wave of magnesium batteries with greater capacities than traditional lithium-ion batteries could be developed using disorganised crystals of magnesium chromium oxide.
Researchers from UCL and University of Illinois at Chicago have published a study showing how to create a material that can reversibly store magnesium ions at high-voltage.
“Lithium-ion technology is reaching the boundary of its capability, so it’s important to look for other chemistries that will allow us to build batteries with a bigger storage capacity and a slimmer design,” said UCL’s Dr Ian Johnson, co-lead author of the study.
Li-ion batteries are limited by their low-capacity carbon anodes. While pure lithium anodes are available, these are dangerously prone to short circuits and fires. Magnesium anodes are comparatively safer, meaning batteries can be made smaller and energy denser.
The researchers created a roughly 5-nanometre thick piece of disordered magnesium chromium oxide material and compared it with a conventional, ordered magnesium chromium oxide material around 7 nanometres wide.
They discovered that the disordered particles showed reversible magnesium extraction and insertion, whereas the ordered material did not. While ordered structures provide clear diffusion pathways to promote the flow of electrons, disordered structures can create new, accessible diffusion pathways.
“This suggests the future of batteries might lie in disordered and unconventional structures, which is an exciting prospect and one we’ve not explored before, as usually disorder gives rise to issues in battery materials,” explained Professor Jawwad Darr from UCL Chemistry.
Scientists from the University of Basel have developed a new method to control the physical state of small groups of molecules or atoms within a network. This technique could be used to store information on a molecular scale and create even denser data storage devices.
The team from Basel created a hexagonal organometallic network covered in precisely defined holes, like a sieve. Xenon gas was introduced, which then filled the holes. By then making temperature changes and applying electrical pulses, the xenon would switch between solid and liquid states.
While these experiments were performed at low temperatures of under -260°C, making them unsuitable for new data storage devices, it does indicate that supramolecular networks can be used to produce tiny and alterable structures.
“We will now test larger molecules as well as short-chain alcohols. These change state at higher temperatures, which means that it may be possible to make use of them,” said Professor Thomas Jung, who supervised the work.