TL;DR
• Researchers discovered a microscopic mechanism that solves in part the outstanding performance achieved by a new class of organic semiconductors known as non-fullerene acceptors (NFAs).
• Green hydrogen often, but certainly not always, leads to CO2 gains. This claim is based on research published in Nature Energy.
• Physicists have made a significant breakthrough in solar cell technology by developing a new analytical model that improves the understanding and efficiency of thin-film photovoltaic (PV) devices.
• A small molecule that naturally serves as a binding site for metals in enzymes also proves useful for separating certain rare earth metals from each other. In a proof of concept, the process extracts europium directly from fluorescent powder in used energy-saving lamps in much higher quantities than existing methods. The researchers are now working on expanding their approach to other rare earth metals. They are in the process of founding a start-up to put the recycling of these raw materials into practice.
• Texas Tech University’s Jennifer Guelfo was part of a research team that found the use of a novel sub-class of per- and polyfluoroalkyl (PFAS) in lithium-ion batteries is a growing source of pollution in air and water.
Green Technology Market
Green technology is an applicable combination of advanced tools and solutions to conserve natural resources and the environment, minimize or mitigate negative impacts from human activities on the environment, and ensure sustainable development. Green technology is also referred to as clean technology or environmental technology which includes technologies, such as IoT, AI, analytics, blockchain, digital twin, security, and cloud, which collect, integrate, and analyze data from various real-time data sources, such as sensors, cameras, and Global Positioning System (GPS).
Green technology, also known as sustainable technology, protects the environment by using various forms of sustainable energy. Some of the best examples of green technologies include solar panels, LED lighting, wind energy, electric vehicles, vertical farming, and composting.
The global Green Technology and Sustainability market size to grow from USD 11.2 billion in 2020 to USD 36.6 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 26.6% during the forecast period. The growing consumer and industrial interest for the use of clean energy resources to conserve environment and the increasing use of Radio Frequency Identification sensors across industries are driving the adoption of green technology and sustainability solutions and services in the market.
Latest Research
Endothermic Charge Separation Occurs Spontaneously in Non‐Fullerene Acceptor/Polymer Bulk Heterojunction
by Kushal Rijal, Neno Fuller, Fatimah Rudayni, Nan Zhang, Xiaobing Zuo, Cindy L. Berrie, Hin‐Lap Yip, Wai‐Lun Chan in Advanced Materials
Solar energy is critical for a clean-energy future. Traditionally, solar energy is harvested using silicon — the same semiconductor material used in everyday electronic devices. But silicon solar panels have drawbacks: for instance, they’re expensive and hard to mount on curved surfaces.
Researchers have developed alternative materials for solar-energy harvesting to solve such shortcomings. Among the most promising of these are called “organic” semiconductors, carbon-based semiconductors that are Earth-abundant, cheaper and environmentally friendly.
“They can potentially lower the production cost for solar panels because these materials can be coated on arbitrary surfaces using solution-based methods — just like how we paint a wall,” said Wai-Lun Chan, associate professor of physics and astronomy at the University of Kansas. “These organic materials can be tuned to absorb light at selected wavelengths, which can be used to create transparent solar panels or panels with different colors. These characteristics make organic solar panels particularly suitable for use in next-generation green and sustainable buildings.”
While organic semiconductors already have been used in the display panel of consumer electronics such as cell phones, TVs and virtual-reality headsets, they have not been widely used in commercial solar panels yet. One shortcoming of organic solar cells has been their low light-to-electric conversion efficiency, about 12% versus single crystalline silicon solar cells that perform at an efficiency of 25%.
According to Chan, electrons in organic semiconductors typically bind to their positive counterparts known as “holes.” In this way, light absorbed by organic semiconductors often produces electrically neutral quasiparticles known as “excitons.”
But the recent development of a new class of organic semiconductors known as non-fullerene acceptors (NFAs) changed this paradigm. Organic solar cells made with NFAs can reach an efficiency closer to the 20% mark. Despite their outstanding performance, it’s remained unclear to the scientific community why this new class of NFAs significantly outperforms other organic semiconductors.
In a breakthrough study, Chan and his team, including graduate students Kushal Rijal (lead author), Neno Fuller and Fatimah Rudayni from the department of Physics and Astronomy, and in collaboration with Cindy Berrie, professor of chemistry at KU, have discovered a microscopic mechanism that solves in part the outstanding performance achieved by an NFA.
The key to this discovery were measurements taken by lead author Rijal using an experimental technique dubbed the “time-resolved two photon photoemission spectroscopy” or TR-TPPE. This method allowed the team to track the energy of excited electrons with a sub-picosecond time resolution (less than a trillionth of one second).
“In these measurements, Kushal [Rijal] observed that some of the optically excited electrons in the NFA can gain energy from the environment instead of losing energy to the environment,” said Chan. “This observation is counterintuitive because excited electrons typically lose their energy to the environment like a cup of hot coffee losing its heat to the surrounding.”
The team, whose work was supported by the Department of Energy’s Office of Basic Energy Sciences, believes this unusual process occurs on the microscopic scale thanks to the quantum behavior of electrons, which allow an excited electron to appear simultaneously on several molecules. This quantum weirdness pairs with the Second law of Thermodynamics, which holds that every physical process will lead to an increase in the total entropy (often known as “disorder”) to produce the unusual energy gain process.
“In most cases, a hot object transfers heat to its cold surroundings because the heat transfer leads to an increase in the total entropy,” said Rijal. “But we found for organic molecules arranged in a specific nanoscale structure, the typical direction of the heat flow is reversed for the total entropy to increase. This reversed heat flow allows neutral excitons to gain heat from the environment and dissociates into a pair of positive and negative charges. These free charges can in turn produce electrical current.”
Based on their experimental findings, the team proposes that this entropy-driven charge separation mechanism allows organic solar cells made with NFAs to achieve a much better efficiency.
“Understanding the underlying charge separation mechanism will allow researchers to design new nanostructures to take advantage of entropy to direct heat, or energy, flow on the nanoscale,” Rijal said. “Despite entropy being a well-known concept in physics and chemistry, it’s rarely been actively utilized to improve the performance of energy conversion devices.”
Worldwide greenhouse gas emissions of green hydrogen production and transport
by Kiane de Kleijne, Mark A. J. Huijbregts, Florian Knobloch, Rosalie van Zelm, Jelle P. Hilbers, Heleen de Coninck, Steef V. Hanssen in Nature Energy
Green hydrogen often, but certainly not always, leads to CO2 gains. This claim is based on research by Kiane de Kleijne from Radboud University and Eindhoven University of Technology. “If you calculate the entire life cycle of green hydrogen production and transport, CO2 gains may be disappointing. However, if green hydrogen is produced from very clean electricity and locally, it can really help reduce emissions.”
It is thought that green hydrogen can make a major contribution to reducing greenhouse gas emissions. Dutch companies are currently investing in developing green hydrogen in countries where green power, needed to produce green hydrogen, can be easily generated, such as Namibia and Brazil. The EU is also aiming to produce 10 million tonnes of green hydrogen and importing another 10 million tonnes by 2030. “Green hydrogen has great potential as a technology due to its versatility and many applications. But unfortunately, I still foresee some bumps in the road,” says environmental scientist De Kleijne.
For over a thousand planned green hydrogen projects, De Kleijne calculated the greenhouse gas emissions associated with producing green hydrogen, including the production of, for example, solar panels, wind turbines and batteries to provide power, and transport by pipeline or ship. “Green hydrogen is produced by splitting water into oxygen and hydrogen in an electrolyser using green electricity. You can then use that hydrogen as a raw material or fuel. Hydrogen made from natural gas is already widely used as a raw material, for example in the chemical industry to produce methanol and ammonia for fertiliser.”
The advantage of green hydrogen is that when splitting water, besides hydrogen, only oxygen is released and no CO2. “However, that does require large amounts of green power,” says the researcher. “You can only reduce emissions if you use green energy, such as wind or solar power. But even then, the emissions from manufacturing wind turbines and solar panels alone add up considerably. If you look at the entire life cycle in this way, green hydrogen often, but certainly not always, leads to CO2 gains. CO2 gains are usually higher when using wind power rather than solar power. This will improve further in the future as more renewable energy will be used to manufacture the wind turbines, solar panels and steel for the electrolyser, for example.”
Hydrogen production results in the lowest emissions in places where there is a lot of sun or wind, like Brazil or Africa. The downside is that this hydrogen must then be transported to Europe. That is technologically challenging and can create a lot of extra emissions. “Transporting green hydrogen over long distances contributes so much to the total emissions that much of the CO2 gains from production in distant, favourable locations is negated,” says De Kleijne. For short distances, transport emissions appear to be lowest for pipelines, while shipping liquid hydrogen is best for long distances.
The key message, according to the scientist, is that we should not claim that technologies such as green hydrogen are completely emission-free. Current calculation methods that form the basis for regulations do not usually consider emissions from what needs to be manufactured to produce hydrogen, such als solar panels and electrolysers, or hydrogen leakage during transportation. In those cases, it might seem that green hydrogen does not produce many emissions, but that is far from the case.
“By looking at emissions over the entire life cycle, we can make a better trade-off between technologies, and identify where improvements can be made in the chain. Furthermore, we can ask ourselves: what is important to produce in the Netherlands and Europe? And when might it be better to move an industry to somewhere else in the world?”
Diode Equation for Sandwich-Type Thin-Film Photovoltaic Devices Limited by Bimolecular Recombination
by Oskar J. Sandberg, Ardalan Armin in PRX Energy
Physicists from Swansea University and Åbo Akademi University have made a significant breakthrough in solar cell technology by developing a new analytical model that improves the understanding and efficiency of thin-film photovoltaic (PV) devices.
For nearly eight decades, the so-called Shockley diode equation has explained how current flows through solar cells; the electrical current that powers up your home or charges the battery bank. However, the new study challenges this traditional understanding for a specific class of next-generation solar cells, namely: thin-film solar cells. These thin-film solar cells, made of flexible, low-cost materials have had limited efficiency due to factors that the existing analytical models couldn’t fully explain. The new study sheds light on how these solar cells achieve optimal efficiency. It reveals a critical balance between collecting the electricity generated by light and minimising losses due to recombination, where electrical charges cancel each other out.
“Our findings provide key insights into the mechanisms driving and limiting charge collection, and ultimately the power-conversion efficiency, in low-mobility PV devices,” said the lead author, Dr Oskar Sandberg of Åbo Akademi University, Finland.
Previous analytical models for these solar cells had a blind spot: “injected carriers” — charges entering the device from the contacts. These carriers significantly impact recombination and limited efficiency.
“The traditional models just weren’t capturing the whole picture, especially for these thin-film cells with low-mobility semiconductors,” explained the principal investigator, Associate Professor Ardalan Armin of Swansea University. “Our new study addresses this gap by introducing a new diode equation specifically tailored to account for these crucial injected carriers and their recombination with those photogenerated.”
“The recombination between injected charges and photogenerated ones is not a huge problem in traditional solar cells such as silicon PV which is hundreds of times thicker than next generation thin film PV such as organic solar cells,” Dr Sandberg added.
Associate Professor Armin said: “One of the brightest theoretical physicists of all times, Wolfgang Pauli once said ‘God made the bulk; the surface was the work of the devil’. As thin film solar cells have much bigger interfacial regions per bulk than traditional silicon; no wonder why they get affected more drastically by “the work of the devil” — that is recombination of precious photogenerated charges with injected ones near the interface!”
This new model offers a new framework for designing more efficient thin solar cells and photodetectors, optimising existing devices, and analysing material properties. It can also aid in training machines used for device optimisation marking a significant step forward in the development of next-generation thin-film solar cells.
Recovery of europium from E-waste using redox active tetrathiotungstate ligands
by Marie A. Perrin, Paul Dutheil, Michael Wörle, Victor Mougel in Nature Communications
Rare earth metals are not as rare as their name suggests. However, they are indispensable for the modern economy. After all, these 17 metals are essential raw materials for digitalisation and the energy transition. They are found in smartphones, computers, screens and batteries — without them, no electric motor would run and no wind turbine would turn. Because Europe is almost entirely dependent on imports from China, these raw materials are considered to be critical.
However, rare earth metals are also critical because of their extraction. They always occur in compound form in natural ores — but as these elements are chemically very similar, they are difficult to separate. Traditional separation processes are therefore very chemical- and energy-intensive and require several extraction steps. This makes the extraction and purification of these metals expensive, resource- and time-consuming and extremely harmful to the environment.
“Rare earth metals are hardly ever recycled in Europe,” says Victor Mougel, Professor at the Laboratory of Inorganic Chemistry at ETH Zurich. A team of researchers led by Mougel wants to change this. “There is an urgent need for sustainable and uncomplicated methods for separating and recovering these strategic raw materials from various sources,” says the chemist.
In a study recently, the team presents a surprisingly simple method for efficiently separating and recovering the rare earth metal europium from complex mixtures including other rare earth metals.
Marie Perrin, a doctoral student in Mougel’s group and first author of the study, explains: “Existing separation methods are based on hundreds of liquid-liquid extraction steps and are inefficient — the recycling of europium has so far been impractical.” In their study, they show how a simple inorganic reagent can significantly improve separation. “This allows us to obtain europium in a few simple steps — and in quantities that are at least 50 times higher than with previous separation methods,” says Perrin.
The key to this technique can be found in small inorganic molecules featuring four sulphur atoms around tungsten or molybdenum: tetrathiometallates. The researchers were inspired by the world of proteins. Tetrathiometallates are found as a binding site for metals in natural enzymes and are used as active substances against cancer and copper metabolism disorders.
For the first time, tetrathiometallates are now also being used as ligands for the separation of rare earth metals. Their unique redox properties come into play here, reducing europium to its unusual divalent state and thus simplifying separation from the other trivalent rare earth metals.
Electronic waste is an important but as yet underutilised source of rare earth metals. “If this source were tapped into, the lamp waste that Switzerland currently sends abroad to be disposed of in a landfill could be recycled here in Switzerland instead,” says Mougels. In this way, lamp waste could serve as an urban mine for europium and make Switzerland less dependent on imports.
In the past, europium was mainly used as phosphor in fluorescent lamps and flat screens, which led to high market prices. As fluorescent lamps are now gradually being phased out, demand has fallen, so that the previous recycling methods for europium are no longer economically viable. More efficient separation strategies are nevertheless desirable and could help to utilise the vast quantities of cheap fluorescent lamp waste whose rare earth metal content is around 17 times higher than in natural ores.
This makes it all the more urgent to recover rare metals at the end of a product’s life and keep them in circulation — but the recovery rate of rare earth elements in the EU is still below one per cent.
In principle, any separation process for rare earth metals can be used both for extraction from ore and for recovery from waste. With their method, however, the researchers are deliberately focussing on recycling the raw materials, as this makes much more ecological and economic sense. “Our recycling approach is significantly more environmentally friendly than all conventional methods for extracting rare earth metals from mineral ores,” says Mougel.
The researchers have patented their technology and are in the process of founding a start-up called REEcover to commercialise it in the future. They are currently working on adapting the separation process for other rare earth metals such as neodymium and dysprosium, which are found in magnets. If this is successful, Marie Perrin wants to build up the start-up after her doctorate and establish the recycling of rare earth metals in practice.
Lithium-ion battery components are at the nexus of sustainable energy and environmental release of per- and polyfluoroalkyl substances
by Jennifer L. Guelfo, P. Lee Ferguson, Jonathan Beck, Melissa Chernick, Alonso Doria-Manzur, Patrick W. Faught, Thomas Flug, Evan P. Gray, Nishad Jayasundara, Detlef R. U. Knappe, Abigail S. Joyce, Pingping Meng, Marzieh Shojaei in Nature Communications
Texas Tech University’s Jennifer Guelfo was part of a research team that found the use of a novel sub-class of per- and polyfluoroalkyl (PFAS) in lithium ion batteries is a growing source of pollution in air and water.
Testing by the research team further found these PFAS, called bis-perfluoroalkyl sulfonimides (bis-FASIs), demonstrate environmental persistence and ecotoxicity comparable to older notorious compounds like perfluorooctanoic acid (PFOA).
Lithium ion batteries are a key part of the growing clean energy infrastructure, with uses in electric cars and electronics, and demand is anticipated to grow exponentially over the next decade.
“Our results reveal a dilemma associated with manufacturing, disposal, and recycling of clean energy infrastructure,” said Guelfo, an associate professor of environmental engineering in the Edward E. Whitacre Jr. College of Engineering. “Slashing carbon dioxide emissions with innovations like electric cars is critical, but it shouldn’t come with the side effect of increasing PFAS pollution. We need to facilitate technologies, manufacturing controls and recycling solutions that can fight the climate crisis without releasing highly recalcitrant pollutants.”
The researchers sampled air, water, snow, soil and sediment near manufacturing plants in Minnesota, Kentucky, Belgium and France. The bis-FASI concentrations in these samples were commonly at very high levels. Data also suggested air emissions of bis-FASIs may facilitate long-range transport, meaning areas far from manufacturing sites may be affected as well. Analysis of several municipal landfills in the southeastern U.S. indicated these compounds can also enter the environment through disposal of products, including lithium ion batteries.
Toxicity testing demonstrated concentrations of bis-FASIs similar to those found at the sampling sites can change behavior and fundamental energy metabolic processes of aquatic organisms. Bis-FASI toxicity has not yet been studied in humans, though other, more well-studied PFAS are linked to cancer, infertility and other serious health harms.
Treatability testing showed bis-FASIs did not break down during oxidation, which has also been observed for other PFAS. However, data showed concentrations of bis-FASIs in water could be reduced using granular activated carbon and ion exchange, methods already used to remove PFAS from drinking water.
“These results illustrate that treatment approaches designed for PFOA and PFOS (perfluorooctanesulfonic acid) can also remove bis-FASIs,” said study author Lee Ferguson, associate professor of environmental engineering at Duke University. “Use of these approaches is likely to increase as treatment facilities are upgraded to comply with newly enacted EPA Maximum Contaminant Levels for PFAS.”
Guelfo and Ferguson emphasize this is a pivotal time for adoption of clean energy technologies that can reduce carbon dioxide emissions.
“We should harness the expertise of multi-disciplinary teams of scientists, engineers, sociologists, and policy makers to develop and promote use of clean energy infrastructure while minimizing the environmental footprint,” Ferguson said.
“We should use the momentum behind current energy initiatives to ensure that new energy technologies are truly clean,” Guelfo added.
Texas Tech University’s Jennifer Guelfo was part of a research team that found the use of a novel sub-class of per- and polyfluoroalkyl (PFAS) in lithium ion batteries is a growing source of pollution in air and water. Testing by the research team further found these PFAS, called bis-perfluoroalkyl sulfonimides (bis-FASIs), demonstrate environmental persistence and ecotoxicity comparable to older notorious compounds like perfluorooctanoic acid (PFOA).
Lithium ion batteries are a key part of the growing clean energy infrastructure, with uses in electric cars and electronics, and demand is anticipated to grow exponentially over the next decade.
“Our results reveal a dilemma associated with manufacturing, disposal, and recycling of clean energy infrastructure,” said Guelfo, an associate professor of environmental engineering in the Edward E. Whitacre Jr. College of Engineering. “Slashing carbon dioxide emissions with innovations like electric cars is critical, but it shouldn’t come with the side effect of increasing PFAS pollution. We need to facilitate technologies, manufacturing controls and recycling solutions that can fight the climate crisis without releasing highly recalcitrant pollutants.”
The researchers sampled air, water, snow, soil and sediment near manufacturing plants in Minnesota, Kentucky, Belgium and France. The bis-FASI concentrations in these samples were commonly at very high levels. Data also suggested air emissions of bis-FASIs may facilitate long-range transport, meaning areas far from manufacturing sites may be affected as well. Analysis of several municipal landfills in the southeastern U.S. indicated these compounds can also enter the environment through disposal of products, including lithium ion batteries.
Toxicity testing demonstrated concentrations of bis-FASIs similar to those found at the sampling sites can change behavior and fundamental energy metabolic processes of aquatic organisms. Bis-FASI toxicity has not yet been studied in humans, though other, more well-studied PFAS are linked to cancer, infertility and other serious health harms.
Treatability testing showed bis-FASIs did not break down during oxidation, which has also been observed for other PFAS. However, data showed concentrations of bis-FASIs in water could be reduced using granular activated carbon and ion exchange, methods already used to remove PFAS from drinking water.
“These results illustrate that treatment approaches designed for PFOA and PFOS (perfluorooctanesulfonic acid) can also remove bis-FASIs,” said study author Lee Ferguson, associate professor of environmental engineering at Duke University. “Use of these approaches is likely to increase as treatment facilities are upgraded to comply with newly enacted EPA Maximum Contaminant Levels for PFAS.”
Guelfo and Ferguson emphasize this is a pivotal time for adoption of clean energy technologies that can reduce carbon dioxide emissions.
“We should harness the expertise of multi-disciplinary teams of scientists, engineers, sociologists, and policy makers to develop and promote use of clean energy infrastructure while minimizing the environmental footprint,” Ferguson said.
“We should use the momentum behind current energy initiatives to ensure that new energy technologies are truly clean,” Guelfo added.
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