University of Cambridge researchers have developed an ‘artificial leaf’ that uses only sunlight, carbon dioxide and water to make syngas. Syngas is a widely-used gas that is currently produced from fossil fuels that could eventually be used to develop a sustainable liquid fuel alternative to gasoline.

The carbon-neutral device sets a new benchmark in the field of solar fuels, after researchers at the University of Cambridge demonstrated that it can directly produce the syngas in a sustainable and simple way.

Image Credit: University of Cambridge. Click image for the largest view.

Rather than running on fossil fuels, the artificial leaf is powered by sunlight, although it still works efficiently on cloudy and overcast days. And unlike the current industrial processes for producing syngas, the leaf does not release any additional carbon dioxide into the atmosphere.

The Cambridge team’s results have been published in the journal Nature Materials.

Syngas is currently made from a mixture of hydrogen and carbon monoxide, and is used to produce a range of commodities, such as fuels, pharmaceuticals, plastics and fertilizers.

Senior author Professor Erwin Reisner from Cambridge’s Department of Chemistry, who has spent seven years working towards this goal said, “You may not have heard of syngas itself, but every day, you consume products that were created using it. Being able to produce it sustainably would be a critical step in closing the global carbon cycle and establishing a sustainable chemical and fuel industry.”

The device Reisner and his colleagues produced is inspired by photosynthesis – the natural process by which plants use the energy from sunlight to turn carbon dioxide into food.

In the artificial leaf, two light absorbers, similar to the molecules in plants that harvest sunlight, are combined with a catalyst made from the naturally abundant element cobalt.

When the device is immersed in water, one light absorber uses the catalyst to produce oxygen. The other carries out the chemical reaction that reduces carbon dioxide and water into carbon monoxide and hydrogen, forming the syngas mixture.

As an added bonus, the researchers discovered that their light absorbers work even under the low levels of sunlight on a rainy or overcast day.

PhD student Virgil Andrei, first author of the paper said, “This means you are not limited to using this technology just in warm countries, or only operating the process during the summer months. You could use it from dawn until dusk, anywhere in the world.”

The research was carried out in the Christian Doppler Laboratory for Sustainable SynGas Chemistry in the University’s Department of Chemistry. It was co-funded by the Austrian government and the Austrian petrochemical company OMV, which is looking for ways to make its business more sustainable.

Michael-Dieter Ulbrich, Senior Advisor at OMV said, “OMV has been an avid supporter of the Christian Doppler Laboratory for the past seven years. The team’s fundamental research to produce syngas as the basis for liquid fuel in a carbon neutral way is ground-breaking.”

Other ‘artificial leaf’ devices have also been developed, but these usually only produce hydrogen. The Cambridge researchers say the reason they have been able to make theirs produce syngas sustainably is thanks the combination of materials and catalysts they used.

These include state-of-the-art perovskite light absorbers, which provide a high photovoltage and electrical current to power the chemical reaction by which carbon dioxide is reduced to carbon monoxide, in comparison to light absorbers made from silicon or dye-sensitized materials. The researchers also used cobalt as their molecular catalyst, instead of platinum or silver. Cobalt is not only lower-cost, but it is better at producing carbon monoxide than other catalysts.

The team is now looking at ways to use their technology to produce a sustainable liquid fuel alternative to petrol.

Syngas is already used as a building block in the production of liquid fuels. “What we’d like to do next, instead of first making syngas and then converting it into liquid fuel, is to make the liquid fuel in one step from carbon dioxide and water,” said Reisner, who is also a Fellow of St John’s College.

Although great advances are being made in generating electricity from renewable energy sources such as wind power and photovoltaics, Reisner says the development of synthetic petrol is vital, as electricity can currently only satisfy about 25% of our total global energy demand. “There is a major demand for liquid fuels to power heavy transport, shipping and aviation sustainably,” he said.

“We are aiming at sustainably creating products such as ethanol, which can readily be used as a fuel,” said Andrei. “It’s challenging to produce it in one step from sunlight using the carbon dioxide reduction reaction. But we are confident that we are going in the right direction, and that we have the right catalysts, so we believe we will be able to produce a device that can demonstrate this process in the near future.”

This is quite a noteworthy breakthrough, and congratulations are in order for a major step now accomplished. The usual questions remain, like how efficient, yield per solar exposed area, lifespan, CO2 recycling, and basic cost. This team has the technology plateau conquered, now to find the market successful product.

Of special note is the comment from Professor Reisner, stating in part, “a critical step in closing the global carbon cycle”. That’s a remark based in reality and common sense everyone could use to measure the relevance of technologies. Thank you Professor.

Researchers at Kyoto University, along with colleagues at the University of Tokyo and Jiangsu Normal University in China have developed a new material that can selectively capture carbon dioxide (CO2) molecules and efficiently convert them into useful organic materials.

This new porous coordination polymer has propeller-shaped molecular structures that enables selectively capturing CO2, and efficiently convert the CO2 into useful carbon materials. Image Credit: Illustration by Mindy Takamiya. Kyoto University. Click image for the largest view.

The team’s study paper has been published in the journal Nature Communications.

The press release asserts “Human consumption of fossil fuels has resulted in rising global CO2 emissions, leading to serious problems associated with global warming and climate change. One possible way to counteract this is to capture and sequester carbon from the atmosphere, but current methods are highly energy intensive.” The low reactivity of CO2 makes it difficult to capture and convert it efficiently.

Ken-ichi Otake, Kyoto University materials chemist from the Institute for Integrated Cell-Material Sciences (iCeMS) said, “We have successfully designed a porous material which has a high affinity towards CO2 molecules and can quickly and effectively convert it into useful organic materials.”

The material is a porous coordination polymer (PCP, also known as MOF; metal-organic framework), a framework consisting of zinc metal ions. The researchers tested their material using X-ray structural analysis and found that it can selectively capture only CO2 molecules with ten times more efficiency than other PCPs.

The material has an organic component with a propeller-like molecular structure, and as CO2 molecules approach the structure, they rotate and rearrange to permit CO2 trapping, resulting in slight changes to the molecular channels within the PCP – this allows it to act as molecular sieve that can recognize molecules by size and shape. The PCP is also recyclable; the efficiency of the catalyst did not decrease even after 10 reaction cycles.

Susumu Kitagawa, materials chemist at Kyoto University said, “One of the greenest approaches to carbon capture is to recycle the carbon dioxide into high-value chemicals, such as cyclic carbonates which can be used in petrochemicals and pharmaceuticals.”

After capturing the carbon, the converted material can be used to make polyurethane, a material with a wide variety of applications including clothing, domestic appliances and packaging.

This work highlights the potential of porous coordination polymers for trapping carbon dioxide and converting into useful materials, opening up an avenue for future research into carbon capture materials.

This is fascinating work in CO2 recycling with an unusual result. A yield of polyurethane quite catches one with a surprise. Perhaps one day we’ll be using CO2 collectors for carbon collection at everyone’s home. Or perhaps not, CO2 is the fundamental food for plants. The source of the food we eat and the oxygen we breath.

A Tokyo Institute of Technology research team has developed an eco-friendly device that uses solar energy to catalyze an electrochemical oxidation reaction with high efficiency.

Green energy sources constitute a hot research field globally because of the current environmental impetus and the pressure to avoid non-renewable energy (fossil fuels). Researchers have been seeking ways to harness and harvest solar energy for decades, and photovoltaic devices, which convert light into electricity, are in high demand.

The study of these devices has progressed much since their interest first sparked in the 1970s after the economic shocks caused by oil prices. While most advances where made for silicon-based solar cells, scientists have demonstrated that organic photovoltaic devices can also achieve acceptable performance.

The structure of the proposed device, showing how the generated holes (h+) are used to facilitate thiol oxidation. The measured current increases dramatically under illumination and application of a slight potential. Image Credit: Tokyo Institute of Technology . Click image for the largest view.

Using organic materials is advantageous because they are printable and paintable as environmentally friendly processes unlike silicon processes. Organic materials also come in great variety, making it possible to tailor them for each specific application.

Organic photovoltaic solar cells consist of an “active layer” sandwiched between two different electrodes (a transparent front electrode and a back electrode). The active layer is where the magic starts; the energy from the photons of the incident light is transferred to the electrons of the material through collisions, exciting them and setting them into motion, leaving behind positively charged pseudo-particles known as “holes.” These do not technically exist, but can be used to approximately describe the electrical behavior of the material. The importance of the electrodes lies in that each one must collect one type of these charged particles (one gathers holes, and the other electrons) to prevent them from recombining in the active layer. The electrons flow through an external circuit that is connected to both electrodes, creating electricity from solar light.

However, it is challenging to collect large numbers of electrons and holes at the electrodes and convert light into electricity with high efficiency. Some researchers have proposed that it would be beneficial to directly use the generated holes or electrons in chemical reactions near the active layer.

Thus motivated, a research team including Dr. Keiji Nagai from Tokyo Tech and Kanazawa University proposed a simple fabrication procedure for an organic photoelectrochemical device that can harvest solar energy to promote a chemical oxidation reaction.  The team’s research paper has been published in the journal Chemical Communications.

Their approach starts with a conventional organic photovoltaic device, which can be easily fabricated and whose characteristics are well known, and mechanically removing the back electrode where holes are collected. The exposed active layer is coated with ZnPc and submerged in thiol. The holes generated by the incident light are directly used for thiol oxidation, which is catalyzed (facilitated) by the ZnPc layer. The excited electrons flow out through the remaining front electrode, generating an electric current.

The simplicity and advantages of the fabrication approach and the measured efficiency when harvesting light energy are very promising.

Dr. Nagai explained, “The removal of the back electrode is a promising and repeatable technique for constructing a well-characterized photoelectrochemical cell.”

The researchers also studied the topographic and electrochemical properties of the active layer coated with ZnPc to elucidate the principles of its catalytic activity.

Dr. Takahashi of Kanazawa University noted, “The effects of the ZnPc coating were clearly observed in our analyses and consist of the effective accumulation of photogenerated holes.”

Environmentally friendly devices such as the proposed one provide more ways to harvest energy from the sun and get us closer to a greener future.

The paint on solar cell does have its allure. While practically everyone dreams of displacing every grid generation source with “renewables” the true opportunity lies in this kind of technology. This tech enables all kinds of low power demand jobs, both those known and so many more possible with a power source and some storage. Remember, all the trendy eco things have to someday face the test of economic viability. So far only wind has managed to force itself on us with government “incentives”.

American Institute of Physics researchers have looked to lithium sulfur batteries because of sulfur’s high theoretical capacity and energy density to develop higher capacity batteries.

Lithium ion batteries aren’t keeping up with energy demands from higher power electronic devices, electric vehicles and smart electric grids. To develop higher capacity batteries, researchers have looked to lithium sulfur batteries because of sulfur’s high theoretical capacity and energy density.

There are still several problems to solve before lithium sulfur batteries can be put into practical applications. The biggest is the shuttling effect that occurs during cycling. This effect causes the diffusion of polysulfides from the cathode, creating capacity loss. It also consumes a lot of fresh lithium and electrolytes, and reduces battery performance.

To solve this problem and improve lithium sulfur battery performance, the researchers created a sandwich-structured electrode using a novel material that traps polysulfides and increases the reaction kinetics.

Another is sulfur’s intrinsically low electrical conductivity and the rapid capacity decay caused by polysulfides escaping from the cathode.

To solve the shuttling problem and improve lithium sulfur battery performance, the authors of the paper published in APL Materials, created a sandwich-structured electrode using a novel material that traps polysulfides and increases the reaction kinetics.

Schematic of the designed structure of LSBs: (a) Nonconfined structure, bare S electrode, (b) partially confined structure, PZ67/S electrode, (c) partially confined structure, S/PZ67 electrode, and (d) fully confined structure, PZ67/S/PZ67 electrode. Image Credit: Beijing Institute of Technology. Click image for the largest view.

ZIF-67 is a metal-organic framework (MOF) constructed from metal ions or metal clusters and organic ligands. It holds great promise in gas storage and separation, catalysis and energy storage. MOF-derived materials are also attractive in energy storage due to their robust structure, porous surface and high conductivity.

A sandwich-structured electrode with sulfur immobilized in between PZ67 layers, as a PZ67/S/PZ67 build, improves the practical energy density of the lithium sulfur battery to three to five times higher than that of lithium ion batteries. The PZ67 is composed of polar materials, and the porous carbon showed a synergistic effect in the chemical interaction, served as a physical barrier, offered a high conductivity to prohibit the polysulfide shuttling effect and enhanced the batteries’ cycling performance.

Author of the paper Siwu Li said, “The porous PZ67 can not only absorb the polysulfides to form a confinement, it can also improve the kinetics of the actual active materials’ reaction during the battery cycling. That means it may also improve the discharge voltage of the battery, and that is a big contribution to improving the energy density of the batteries.”

Li also noted that the sandwich-structured electrode that confines soluble polysulfides could be useful for anyone working to confine soluble materials. His team plans to continue their work in order to scale up the process of fabricating the hybrid electrode using a hot pressing procedure. They also plan to address instabilities on the anode side of lithium sulfur batteries, possibly by adding a protective layer.

This is quite good news for the consumer hoping for more battery capacity or simply a smaller unit with equivalent energy. While the press release isn’t saying how expensive or complex construction might be, one wouldn’t be surprised to read the cost and complexity are not far away from today’s products. The wild card is the PZ67, which isn’t a commercial quantity item, but could be, and that will tell the marketability tale.

The story for lithium sulfur batteries isn’t over, lacking an answer for the anode, but this team sure looks to have good answers for a far better battery solution.

Ohio State University researchers, in collaboration with scientists around the world, have made a discovery that could provide new insights into how superconductors might move energy more efficiently to power homes, industries and vehicles. Their work showed that graphene – a material composed of a single layer of carbon atoms – is more likely to become a superconductor than originally thought possible.

Their work has been published in the journal Science Advances and showed that graphene is more likely to become a superconductor.

Schematic diagram of the device geometry. Image Credit: Ohio State University. Click image for the largest view.

Jeanie Lau, a professor of physics at Ohio State and lead author of the paper said, “Graphene by itself can conduct energy, as a normal metal is conductive, but it is only recently that we learned it can also be a superconductor, by making a so-called ‘magic angle’ – twisting a second layer of graphene on top of the first. And that opens possibilities for additional research to see if we can make this material work in the real world.”

Unlike most conventional conductors, superconductors are metals that can conduct electricity without resistance, thus suffering no loss of energy.

Graphene is two-dimensional crystal – a perfectly flat piece of carbon – and, as a single layer, is not a superconductor. But earlier this year, scientists at the Massachusetts Institute of Technology published research that showed that graphene could become a superconductor if one piece of graphene were laid on top of another piece and the layers twisted to a specific angle – what they termed “the magic angle.”

That magic angle, scientists thought, was between 1 degree and 1.2 degrees – a very precise angle.

“The question is, the magic angle, how magic does it have to be?” said Emilio Codecido, a graduate student in Lau’s lab and a co-author on the paper.

The Ohio State team found that the magic angle appears to be less magical than originally thought. Their work found that graphene layers still superconducted at a smaller angle, around 0.9 degrees. It is a small distinction, but it could open the possibility of new experiments to investigate graphene as a potential superconductor in the real world. So far, superconducting is limited outside of scientific laboratories because in order to superconduct electricity, the electric lines must be kept at extremely low temperatures.

Marc Bockrath, a co-author of the paper and physics professor at Ohio State said, “This research pushed our understanding of superconductors and the magic angle a little further than the theory and prior experiments might have expected.”

Codecido pointed out, “Superconductivity could revolutionize many industries – electric transmission lines, communication lines, transportation, trains. Superconductivity in twisted bilayer graphene will teach us about superconductivity at much higher temperatures, temperatures that will be useful for real-world applications. That’s where future work will be focused.”

Perhaps this is the doorway to readily available superconductivity. Meanwhile graphene isn’t mass produced or low cost in what might be thought of as commercial volumes. But there will be a product someday that triggers mass production. Then we’ll see if this idea is the path to common superconductivity. Unless another idea breaks out before then.


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