University of Basel researchers continue to improve the performance dye sensitized solar cells with sensitizers using iron – a commonly available and environmentally friendly metal.

Solar energy plays an important role in the fight against climate change as a substitute for fossil fuels. Dye-sensitized solar cells promise to be a low-cost supplement to the photovoltaic systems we know today. Their key feature is the dye sensitizers attached to their surface.

Sensitizers are intensely colored compounds that absorb light and convert its energy into electricity by releasing electrons and “injecting” them into the semiconductor. So far, the sensitizers used in the dye-sensitized solar cells have either been relatively short-lived or demanded the use of very rare and expensive metals. The holy grail of photovoltaic research is therefore the development of sensitizers using iron – a metal that is both environmentally friendly and the most abundant transition metal on our planet.

For many years, experts considered iron compounds to be unsuitable for these applications because their excited state following light absorption is too short-lived to be of use for energy production. This changed around seven years ago with the discovery of a new class of iron compounds with what are known as N-heterocyclic carbenes (NHCs).

The research group headed by Professor Edwin Constable and Professor Catherine Housecroft at the University of Basel’s Department of Chemistry has been working with these compounds for a number of years. The team led by project leader Dr. Mariia Becker has now reported on their results with a sensitizer based on a new family of NHCs in the specialist journal Dalton Transactions.

Dr. Becker explained, “We knew that we had to develop materials that would stick to the surface of a semiconductor and whose character would simultaneously allow the arrangement of the functional light-absorbing components on the surface to be optimized.”

The researchers used a two-pronged approach to these challenges: first, they incorporated carboxylic acid groups (as found in vinegar) into the iron compound in order to bind it to the semiconductor’s surface. Secondly, they made the compounds “greasy” by adding long carbon chains that made the surface layer more fluid and easier to anchor.

These dye-sensitized solar cell prototypes only achieved overall efficiency of 1 percent, while today’s midstream commercially available solar cells reach around 20 percent efficiency. “Nevertheless, the results represent a milestone that will encourage further research into these new materials,” said Becker with conviction.

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For solar cells to become a true mass market product without government incentives and subsidies whose cost is borne by everyone only to benefit a few – this kind of research is critical and deserves support and attention. So far solar is not truly practical. When it really is, it will be the normal choice for everyone.

Northern Illinois University scientists have described development of a cost-effective Scotch-tape-like film that can be applied to perovskite solar cells and capture 99.9% of leaked lead in the event of solar cell damage.

The researchers at Northern Illinois University and the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) in Golden, Colorado, are reporting a potential breakthrough that could help speed commercialization of highly promising perovskite solar cells (PSCs) for use in solar panels.

In a brief communication to the journal Nature Sustainability, the scientists described the development of the cost-effective Scotch-tape-like film.

The industry-ready film would help alleviate health and safety concerns without compromising perovskite solar-cell performance or operation, according to the research team. Testing of the lead-absorbing film included submerging damaged cells in water.

A layer of lead-absorbent material is bladed onto standard solar ethylene vinyl acetate (EVA) film. Image Credit: Xun Li, Northern Illinois University. Click image for the largest view.

NIU Chemistry Professor Tao Xu, who co-led the research with Kai Zhu of NREL’s National Renewable Energy Laboratory said, “Our practical approach mitigates the potential lead-leakage to a level safer than the standard for drinking water. We can easily apply our lead-absorbing materials to off-the-shelf films currently used to encapsulate silicon-based solar cells at the end of their production, so existing fabrication processes for PSCs would not be disrupted. At the end of PSC production, the films would be laminated to the solar cell.”

An emerging class of solar cells, PSCs are considered rising stars in the field of solar energy because of their high-power conversion efficiency (exceeding 25.5%) and low manufacturing costs. But PSCs are not yet commercially available on a widescale basis because key challenges remain, including potential lead-toxicity issues.

Small amounts of water-soluble lead continue to be essential components to the light-absorbing layer of high efficiency PSCs, which must be able to withstand severe weather for commercial viability. Significant lead leakage from damaged cells would cause toxic health and safety concerns.

To counter those concerns, the transparent tapes use lead absorbents made with a standard solar ethylene vinyl acetate (EVA) film and a pre-laminated layer of lead-absorbing material. The tape can be attached to both sides of fabricated PSCs, as in the standard encapsulation process used in silicon-based solar cells.

Among the tests used to assess the durability of the new technology, the scientists exposed the film-encapsulated PSCs to outdoor, rooftop conditions for three months. Razor blades and hammers were used to then damage the solar cells before they were submerged in water for seven days. The lead-absorbing tapes exhibited a lead-sequestration efficiency of over 99.9%.

Xu noted, “Perovskite solar cells hold great hope for a more sustainable future. This work offers a convenient and industry-ready method to diminish the potential lead leakage from lead-containing PSCs, facilitating future commercialization of perovskite-based photovoltaic technology.”

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This work might be the opening for perovskite to make it to the mass market. The question that remains is the longevity of the tape. It will have to out last the panel and the period needed to get the panel recycled. Therein lies the problem, just how many would be recycled instead of simply dumped in a land fill.

Texas A&M University researchers recently published a comprehensive review article on how carbon dioxide can be isolated through reduction reactions and then transformed into value-added chemicals for fuels. They are able to show a path to recycle and repurpose excess carbon dioxide.

Image Credit: Texas A&M University. Click image for the largest view.

While a very small percentage of the atmosphere, carbon dioxide plays a vital role in sustaining life on our planet.

A team of researchers in the Artie McFerrin Department of Chemical Engineering at Texas A&M University recently published a comprehensive review in the journal ACS Applied Energy Materials. The research was led Dr. Abdoulaye Djire, assistant professor in the chemical engineering department, and co-authored by Dr. Zhi Qiao, a former postdoctoral researcher for the department.

Denis Johnson, the first author on the study and a doctoral student in the chemical engineering department said, “People are looking into innovative ways to mitigate global warming and minimize our impacts on the environment. Through scientific advancements, such as our own, we remain hopeful that one day we may be able to start reversing what has already been done.”

As Johnson suggests, a potential contributor to global warming is carbon dioxide. According to an assessment by the U.S. Energy Information Administration, unless the current energy structure is changed, carbon dioxide levels in the atmosphere will continue to increase.

Currently, there are several methods to decrease carbon dioxide’s negative impacts. One such method is decarbonization, whereby carbon is simply removed from supply chains. Despite its promise, decarbonization requires using other carbon sources, such as liquid fuels and feedstocks, deeming it unsustainable. Another method called carbon sequestration, where carbon is removed from the atmosphere, is not economically viable due to rising industry costs and the lack of technology capable of performing this task.

Johnson explained, “Excess carbon dioxide does more harm than good. Research has found that products derived from carbon dioxide, whether they were carbon monoxide, methanol or ethanol, all have much greater use than carbon dioxide alone with the included benefit of posing less health and environmental hazards.”

Hence, the researchers are investigating if carbon dioxide reduction reactions, converting carbon dioxide to make other carbon compounds using electricity, are feasible solutions.

Carbon dioxide can be removed from emissions or the atmosphere through the use of amine columns, or similar carbon capture technologies, and purified. Once the carbon dioxide is purified, the researchers can then perform the carbon dioxide reduction reaction using a transition metal to initiate the electrochemical reaction.

The researchers said one of the advantages of this chemical process is that depending on which transition metal is used, copper or nickel for example, different products can be made. The carbon dioxide can be recycled for making a variety of carbonaceous products, such as propanol for medicines or ethanol for fuels, whose value and versatilities are much more significant.

“Let’s say we get back every amount of carbon dioxide we put in, we could potentially use the carbon dioxide to produce ethanol, which can then be mixed back into fuel using recycled carbon dioxide,” said Johnson.

The article starts by reviewing the electrochemical methods currently being used to reduce the damaging effects of carbon dioxide, providing a helpful resource for other researchers in the field. The article follows with tutorials on the techniques used to help analyze the catalysts and the products of the electrochemical carbon dioxide reduction process.

“This process can fundamentally change the impacts of carbon dioxide, making it a form of renewable energy while simultaneously providing carbon sources to industries dependent on the product, reducing its negative environmental impact,” said Professor Djire. “This work summarizes what we know about carbon dioxide recycling and transformation, and how we can carry this information into the future.”

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Your humble author had quite the internal debate on whether to publish a post on this group’s work. The benefits of recycling CO2 outweigh the climate change hysteria. Folks tend to forget there is such a thing as not enough CO2 in the atmosphere to support life on the planet Earth. On the other hand today’s CO2 is less than half of “normal” by the ice core studies’ results. Its all quite . . . dubious, putting it kindly. After all, the first doomsday “Sky Is Falling” claims are soon to be 50 years old and nothing has happened to the climate except it warmed up a bit and is now getting a bit colder.

Researchers at Dalian Maritime University, Marine Engineering College reported they have developed flexible power generators that mimic the way seaweed sways to efficiently convert surface and underwater waves into electricity to power marine-based devices. Ocean waves can be powerful, containing enough energy to push around sand, pebbles and even boulders during storms. These waves, as well as smaller, more gentle ones, could be tapped as a source of renewable energy.

The research team’s study paper has been published in the journal ACS Nano.

Across many coastal zones, networks of sensors collect information on the water’s currents, tides and clarity to help ships navigate and to monitor water quality. This “marine internet of things” is powered mostly by batteries that have to be replaced from time to time, which is time-consuming and expensive. Wind and solar power could be used, but they aren’t suitable for underwater applications.

Looking to harness the ocean’s continuous movement as a renewable energy source, researchers initially developed floating devices that converted wave energy into electricity using rotating magnets. But these devices were inefficient with less frequent waves, such as those found underwater. Triboelectric nanogenerators (TENGs), which rely on surfaces coming in contact to produce static electricity, could be a way to address this challenge because of their effectiveness for harvesting low-frequency, low-amplitude wave energy.

Minyi Xu, Zhong Lin Wang and colleagues were inspired by plants living on the seafloor to create flexible TENGs. The researchers wanted to copy the way strands of seaweed vibrate to charge bendable triboelectric surfaces, harvesting the movement of waves into electricity to power floating and submerged marine sensors.

To make the triboelectric surfaces, the researchers coated 1.5-inch by 3-inch strips of two different polymers in a conductive ink. Then a small sponge was wedged between the strips, creating a thin air gap, and the whole unit was sealed, creating a TENG.

In tests, as the TENGs were moved up and down in water, they bent back and forth, generating electricity. When the researchers put the TENGs in water pressures similar to those found underwater in coastal zones, they found that the air gap between the two conductive materials decreased. However, the devices still generated a current at 100 kPa of pressure – the same pressure that typically exists at a 30-foot water depth where there is almost no underwater wave movement.

Finally, the researchers used a wave tank to demonstrate that multiple TENGs could be used as a mini underwater power station, supplying energy for either a thermometer, 30 LEDs or a blinking miniature lighthouse LED beacon. The researchers say their seaweed-like TENG could reduce the reliance on batteries in coastal zones, including for marine sensors.

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This team’s work looks quite innovative. One would expect that the technology will be very welcome and assist in getting more and better data. One obvious question is going to be longevity – how long will it remain flexible until the ocean creatures encrust it solid?

A new electrocatalyst called a-CuTi@Cu converts carbon dioxide (CO2 ) into liquid fuels. An active copper centered on an amorphous copper/titanium alloy produces ethanol, acetone, and n-butanol with high efficiency.

An amorphous copper/titanium alloy produces ethanol, acetone, and n-butanol with high efficiency. Image Credit: Hefei National Laboratory for Physical Sciences University of Science and Technology of China, Xi’an Shiyou University & Wiley Online Library. Click image for the largest view.

The research has been reported by a team of Chinese researchers in the journal Angewandte Chemie. The team includes members from from Foshan University (Foshan, Guangdong), the University of Science and Technology of China (Hefei, Anhui), and Xi’an Shiyou University (Xi’an, Shaanxi), and are led by Fei Hu, Tingting Kong, Jun Jiang, and Yujie Xiong.

Most of our global energy demands are still being met by burning fossil fuels, which contributes to the release of CO2. To reduce CO2 releases, we must look for opportunities to use and recycle CO2 as a raw material for basic chemicals.

Through electrocatalytic conversion of CO2 using renewable energy, a climate-neutral, artificial carbon cycle could be established. Excess energy produced by photovoltaics and wind energy could be stored through the electrocatalytic production of fuels from CO2. These could then be combusted as needed.

Conversion into liquid fuels would be advantageous because they have high energy density and are safe to store and transport. However, the electrocatalytic formation of products with two or more carbon atoms (C2+) is very challenging.

The team has developed a novel electrocatalyst that efficiently converts CO2 to liquid fuels with multiple carbon atoms (C2-4). The primary products are ethanol, acetone, and n-butanol.

To make the electrocatalyst, thin ribbons of a copper/titanium alloy are etched with hydrofluoric acid to remove the titanium from the surface. This results in a material named a-CuTi@Cu, with a porous copper surface on an amorphous CuTi alloy.

The alloy has catalytically active copper centers with remarkably high activity, selectivity, and stability for the reduction of CO2 to C2+ products (total faradaic efficiency of about 49% at 0.8 V vs. reversible hydrogen electrode for C2-4 (the number of carbon atoms in the respective molecule) and it is stable for at least three months). In contrast, pure copper foil produces C1 products but hardly any C2+ products.

The reaction involves a multistep electron-transfer process via various intermediates. In the new electrocatalyst, the inactive titanium atoms below the surface actually play an important role; they increase the electron density of the Cu atoms on the surface. This stabilizes the adsorption of *CO, the key intermediate in the formation of multicarbon products, allows for high coverage of the surface with *CO, and lowers the energy barrier for di- and trimerization of the *CO as new carbon-carbon bonds are formed.

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This report follows the one last week that offered a natural gas product (a C1 product) from CO2. But this time the results are in the C2-4 range – that offers more variety. This technology has just popped from an idea into reality and looks to be taking off fast. How far and fast it can get is anyone’s guess for now. A rooftop fuel making device may have a lot more consumer appeal than a solar panel array. We’re going to be watching this technology.


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