It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Scientists capture X-rays from upward positive lightning
EPFL researchers have for the first time recorded X-rays being produced at the beginning of upward positive lightning flashes; an observation that gives important insight into the origins of this rare – and particularly dangerous – form of lightning
Globally, lightning is responsible for over 4,000 fatalities and billions of dollars in damage every year; Switzerland itself weathers up to 150,000 strikes annually. Understanding exactly how lightning forms is key for reducing risk, but because lightning phenomena occur on sub-millisecond timescales, direct measurements are extremely difficult to obtain.
Now, researchers from the Electromagnetic Compatibility Lab, led by Farhad Rachidi, in EPFL’s School of Engineering have for the first time directly measured an elusive phenomenon that explains a lot about the birth of a lightning bolt: X-ray radiation. In a collaborative study with the University of Applied Sciences of Western Switzerland and Uppsala University in Sweden, they recorded lightning strikes at the Säntis tower in northeastern Switzerland, identifying X-rays associated with the beginning of upward positive flashes. These flashes start with negatively charged tendrils (leaders) that ascend stepwise from a high-altitude object, before connecting with a thundercloud, transferring positive charge to the ground.
“At sea level, upward flashes are rare, but could become the dominant type at high altitudes. They also have the potential to be more damaging, because in an upward flash, lightning remains in contact with a structure for longer than it does during a downward flash, giving it more time to transfer electrical charge,” explains Electromagnetic Compatibility Lab PhD candidate Toma Oregel-Chaumont.
Although X-ray emissions have previously been observed from other types of lightning, this is the first time they have been captured from upward positive flashes. Oregel-Chaumont, the first author on a recent Nature Scientific Reports paper describing the observations, says that they offer valuable insights into how lightning – and upward lightning in particular – forms.
“The actual mechanism by which lightning initiates and propagates is still a mystery. The observation of upward lightning from tall structures like the Säntis tower makes it possible to correlate X-ray measurements with other simultaneously measured quantities, like high-speed video observations and electric currents.”
A unique observation opportunity
It’s perhaps not surprising that the novel observations were made in Switzerland, as the Säntis tower offers unique and ideal measurement conditions. The 124-meter tower is perched atop a high peak of the Appenzell Alps, making it a prime lightning target. There is a clear line of sight from neighboring peaks, and the expansive research facility is packed with
high-speed cameras, X-ray detectors, electric field sensors, and current-measuring devices.
Crucially, the speed and sensitivity of this equipment allowed the team to see a difference between negative leader steps that emitted X-rays and those that did not, supporting a theory of lightning formation known as the cold runaway electron model. In a nutshell, the association of X-rays with very rapid electric field changes supported the theory that sudden increases in the air’s electric field causes ambient electrons to “run away” and become a plasma: lightning.
“As a physicist, I like to be able to understand the theory behind observations, but this information is also important for understanding lightning from an engineering perspective: More and more high-altitude structures, like wind turbines and aircraft, are being built from composite materials. These are less conductive than metals like aluminum, so they heat up more, making them vulnerable to damage from upward lightning,” Oregel-Chaumont says.
The observations at Säntis – which receives over 100 lightning strikes every year – are ongoing. Next, the scientists plan to add a microwave sensor to the tower’s arsenal of equipment; this could help determine whether the cold runaway model also applies to downward lightning, as unlike X-rays, microwaves can be measured from the clouds.
Energy scientists unravel the mystery of gold’s glow
EPFL researchers have developed the first comprehensive model of the quantum-mechanical effects behind photoluminescence in thin gold films; a discovery that could drive the development of solar fuels and batteries.
ECOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE
Luminescence, or the emission of photons by a substance exposed to light, has been known to occur in semiconductor materials like silicon for hundreds of years. The nanoscale behavior of electrons as they absorb and then re-emit light can tell researchers a great deal about the properties of semiconductors, which is why they are often used as probes to characterize electronic processes, like those occurring inside solar cells.
In 1969, scientists discovered that all metals luminesce to some degree, but the intervening years failed to yield a clear understanding of how this occurs. Renewed interest in this light emission, driven by nanoscale temperature mapping and photochemistry applications, has reignited the debate surrounding its origins. But the answer was still unclear – until now.
“We developed very high-quality metal gold films, which put us in a unique position to elucidate this process without the confounding factors of previous experiments,” says Giulia Tagliabue, head of the Laboratory of Nanoscience for Energy Technologies (LNET) in the School of Engineering.
In a recent study published in Light: Science and Applications, Tagliabue and the LNET team focused laser beams at the extremely thin – between 13 and 113 nanometers – gold films, and then analyzed the resulting faint glow. The data generated from their precise experiments was so detailed – and so unexpected – that they collaborated with theoreticians at the Barcelona Institute of Science and Technology, the University of Southern Denmark, and the Rensselaer Polytechnic Institute (USA) to rework and apply quantum mechanical modelling methods.
The researchers’ comprehensive approach allowed them to settle the debate surrounding the type of luminescence emanating from the films – photoluminescence – which is defined by the specific way electrons and their oppositely charged counterparts (holes) behave in response to light. It also allowed them to produce the first complete, fully quantitative model of this phenomenon in gold, which can be applied to any metal.
Unexpected quantum effects
Tagliabue explains that, using a thin film of monocrystalline gold produced with a novel synthesis technique, the team studied the photoluminescence process as they made the metal thinner and thinner. “We observed certain quantum mechanical effects emerging in films of up to about 40 nanometers, which was unexpected, because normally for a metal, you don’t see such effects until you go well below 10 nm,” she says.
These observations provided key spatial information about exactly where the photoluminescence process occurred in the gold, which is a prerequisite for the metal’s use as a probe. Another unexpected outcome of the study was the discovery that the gold’s photoluminescent (Stokes) signal could be used to probe the material’s own surface temperature – a boon for scientists working at the nanoscale.
“For many chemical reactions on the surface of metals, there is a big debate about why and under what conditions these reactions occur. Temperature is a key parameter, but measuring temperature at the nanoscale is extremely difficult, because a thermometer can influence your measurement. So, it’s a huge advantage to be able to probe a material using the material itself as the probe,” Tagliabue says.
A gold standard for solar fuel development
The researchers believe their findings will allow metals to be used to obtain unprecedentedly detailed insights into chemical reactions, especially those involved in energy research. Metals like gold and copper – the LNET’s next research target – can trigger certain key reactions, like the reduction of carbon dioxide (CO2) back into carbon-based products like solar fuels, which store solar energy in chemical bonds.
“To combat climate change, we are going to need technologies to convert CO2 into other useful chemicals one way or another,” says LNET postdoc Alan Bowman, the study’s first author.
“Using metals is one way to do that, but if we don’t have a good understanding of how these reactions happen on their surfaces, then we can’t optimize them. Luminescence offers a new way to understand what is happening in these metals.”
Overview of the experimental workflow. (A) Participants fill in a survey about their demographic information and political orientation. (B) Every 5 minutes, participants are randomly assigned to one of four treatment conditions. The two players then debate for 10 minutes on an assigned proposition, randomly holding the PRO or CON standpoint as instructed. (C) After the debate, participants fill out another short survey measuring their opinion change. Finally, they are debriefed about their opponent's identity. Credit: arXiv (2024). DOI: 10.48550/arxiv.2403.14380
A new EPFL study has demonstrated the persuasive power of large language models, finding that participants debating GPT-4 with access to their personal information were far more likely to change their opinion compared to those who debated humans.
"On the internet, nobody knows you're a dog." That's the caption to a famous 1990s cartoon showing a large dog with his paw on a computer keyboard. Fast forward 30 years, replace "dog" with "AI" and this sentiment was a key motivation behind a new study to quantify the persuasive power of today's large language models (LLMs).
"You can think of all sorts of scenarios where you're interacting with a language model although you don't know it, and this is a fear that people have—on the internet are you talking to a dog or a chatbot or a real human?" asked Associate Professor Robert West, head of the Data Science Lab in the School of Computer and Communication Sciences. "The danger is superhuman like chatbots that create tailor-made, convincing arguments to push false or misleading narratives online."
AI and personalization
Early work has found that language models can generate content perceived as at least on par and often more persuasive than human-written messages, however there is still limited knowledge about LLMs' persuasive capabilities in direct conversations with humans, and how personalization—knowing a person's gender, age and education level—can improve their performance.
"We really wanted to see how much of a difference it makes when the AI model knows who you are (personalization)—your age, gender, ethnicity, education level, employment status and political affiliation—and this scant amount of information is only a proxy of what more an AI model could know about you through social media, for example," West continued.
Human v AI debates
In a pre-registered study, the researchers recruited 820 people to participate in a controlled trial in which each participant was randomly assigned a topic and one of four treatment conditions: debating a human with or without personal information about the participant, or debating an AI chatbot (OpenAI's GPT-4) with or without personal information about the participant.
This setup differed substantially from previous research in that it enabled a direct comparison of the persuasive capabilities of humans and LLMs in real conversations, providing a framework for benchmarking how state-of-the-art models perform in online environments and the extent to which they can exploit personal data.
Their article, "On the Conversational Persuasiveness of large language models: A Randomized Controlled Trial," posted to the arXiv preprint server, explains that the debates were structured based on a simplified version of the format commonly used in competitive academic debates and participants were asked before and afterwards how much they agreed with the debate proposition.
The results showed that participants who debated GPT-4 with access to their personal information had 81.7% higher odds of increased agreement with their opponents compared to participants who debated humans. Without personalization, GPT-4 still outperformed humans, but the effect was far lower.
Cambridge Analytica on steroids
Not only are LLMs able to effectively exploit personal information to tailor their arguments and out-persuade humans in online conversations through microtargeting, they do so far more effectively than humans.
"We were very surprised by the 82% number and if you think back to Cambridge Analytica, which didn't use any of the current tech, you take Facebook likes and hook them up with an LLM, the Language Model can personalize its messaging to what it knows about you. This is Cambridge Analytica on steroids," said West.
"In the context of the upcoming U.S. elections, people are concerned because that's where this kind of technology is always first battle tested. One thing we know for sure is that people will be using the power of large language models to try to swing the election."
One interesting finding of the research was that when a human was given the same personal information as the AI, they didn't seem to make effective use of it for persuasion. West argues that this should be expected—AI models are consistently better because they are almost every human on the internet put together.
The models have learned through online patterns that a certain way of making an argument is more likely to lead to a persuasive outcome. They have read many millions of Reddit, Twitter and Facebook threads, and been trained on books and papers from psychology about persuasion. It's unclear exactly how a model leverages all this information but West believes this is a key direction for future research.
"LLMs have shown signs that they can reason about themselves, so given that we are able to interrogate them, I can imagine that we could ask a model to explain its choices and why it is saying a precise thing to a particular person with particular properties. There's a lot to be explored here because the models may be doing things that we don't even know about yet in terms of persuasiveness, cobbled together from many different parts of the knowledge that they have."
More information: Francesco Salvi et al, On the Conversational Persuasiveness of Large Language Models: A Randomized Controlled Trial, arXiv (2024). DOI: 10.48550/arxiv.2403.14380
Machine learning enables viability of vertical-axis wind turbines
EPFL researchers have used a genetic learning algorithm to identify optimal pitch profiles for the blades of vertical-axis wind turbines, which despite their high energy potential, have until now been vulnerable to strong gusts of wind.
If you imagine an industrial wind turbine, you likely picture the windmill design, technically known as a horizontal-axis wind turbine (HAWT). But the very first wind turbines, which were developed in the Middle East around the 8th century for grinding grain, were vertical-axis wind turbines (VAWT), meaning they spun perpendicular to the wind, rather than parallel.
Due to their slower rotation speed, VAWTs are less noisy than HAWTs and achieve greater wind energy density, meaning they need less space for the same output both on- and off-shore. The blades are also more wildlife-friendly: because they rotate laterally, rather than slicing down from above, they are easier for birds to avoid.
With these advantages, why are VAWTs largely absent from today’s wind energy market? As Sébastien Le Fouest, a researcher in the School of Engineering Unsteady Flow Diagnostics Lab explains, it comes down to an engineering problem – air flow control – that he believes can be solved with a combination of sensor technology and machine learning. In a paper recently published in Nature Communications, Le Fouest and UNFOLD head Karen Mulleners describe two optimal pitch profiles for VAWT blades, which achieve a 200% increase in turbine efficiency and a 77% reduction in structure-threatening vibrations.
“Our study represents, to the best of our knowledge, the first experimental application of a genetic learning algorithm to determine the best pitch for a VAWT blade,” Le Fouest says.
Turning an Achilles’ heel into an advantage
Le Fouest explains that while Europe’s installed wind energy capacity is growing by 19 gigawatts per year, this figure needs to be closer to 30 GW to meet the UN’s 2050 objectives for carbon emissions.
“The barriers to achieving this are not financial, but social and legislative – there is very low public acceptance of wind turbines because of their size and noisiness,” he says.
Despite their advantages in this regard, VAWTs suffer from a serious drawback: they only function well with moderate, continuous air flow. The vertical axis of rotation means that the blades are constantly changing orientation with respect to the wind. A strong gust increases the angle between air flow and blade, forming a vortex in a phenomenon called dynamic stall. These vortices create transient structural loads that the blades cannot withstand.
To tackle this lack of resistance to gusts, the researchers mounted sensors onto an actuating blade shaft to measure the air forces acting on it. By pitching the blade back and forth at different angles, speeds, and amplitudes, they generated series of ‘pitch profiles’. Then, they used a computer to run a genetic algorithm, which performed over 3500 experimental iterations. Like an evolutionary process, the algorithm selected for the most efficient and robust pitch profiles, and recombined their traits to generate new and improved ‘offspring’.
This approach allowed the researchers not only to identify two pitch profile series that contribute to significantly enhanced turbine efficiency and robustness, but also to turn the biggest weakness of VAWTs into a strength.
“Dynamic stall – the same phenomenon that destroys wind turbines – at a smaller scale can actually propel the blade forward. Here, we really use dynamic stall to our advantage by redirecting the blade pitch forward to produce power,” Le Fouest explains. “Most wind turbines angle the force generated by the blades upwards, which does not help the rotation. Changing that angle not only forms a smaller vortex – it simultaneously pushes it away at precisely the right time, which results in a second region of power production downwind.”
The Nature Communications paper represents Le Fouest’s PhD work in the UNFOLD lab. Now, he has received a Swiss National Science Foundation (SNSF) BRIDGE grant to build a proof-of-concept VAWT. The goal is to install it outdoors, so that it can be tested as it responds in real time to real-world conditions.
“We hope this air flow control method can bring efficient and reliable VAWT technology to maturity so that it can finally be made commercially available,” Le Fouest says.
This work benefited from the SNSF's "Assistant Professor (AP) Energy Grants" instrument. The call for proposals, launched between 2013 and 2016 as part of the Swiss government's Energy Strategy 2050, aimed to fund the launch of new energy-related research projects in newly opened laboratories. Read the SNSF press release.
In our rapidly industrialized world, the quest for sustainable materials has never been more urgent. Plastics, ubiquitous in daily life, pose significant environmental challenges, primarily due to their fossil fuel origins and problematic disposal.
Now, a study led by Jeremy Luterbacher's team at EPFL unveils a pioneering approach to producing high-performance plastics from renewable resources. The research, published in Nature Sustainability, introduces a novel method for creating polyamides – a class of plastics known for their strength and durability, the most famous of which are nylons – using a sugar core derived from agricultural waste.
The new method leverages a renewable resource, and also achieves this transformation efficiently and with minimal environmental impact.
“Typical, fossil-based plastics need aromatic groups to give rigidity to their plastics – this gives them performance properties like hardness, strength and high temperature resistance,” says Luterbacher. “Here, we get similar results but use a sugar structure, which is ubiquitous in nature and generally completely non-toxic, to provide rigidity and performance properties.”
Lorenz Manker, the study’s lead-author, and his colleagues developed a catalyst-free process to convert dimethyl glyoxylate xylose, a stabilized carbohydrate made directly from biomass such as wood or corn cobs, into high-quality polyamides. The process achieves an impressive atom efficiency of 97%, meaning almost all the starting material is used in the final product, which drastically reduces waste.
The bio-based polyamides exhibit properties that can compete with their fossil counterparts, offering a promising alternative for various applications. What's more, the materials demonstrated significant resilience through multiple cycles of mechanical recycling, maintaining their integrity and performance, which is a crucial factor for managing the lifecycle of sustainable materials.
The potential applications for these innovative polyamides are vast, ranging from automotive parts to consumer goods, all with a significantly reduced carbon footprint. The team's techno-economic analysis and life-cycle assessment suggest these materials could be competitively priced against traditional polyamides including nylons (e.g. nylon 66), with a global warming potential reduction of up to 75%.
The production of these materials is now being scaled up by the EPFL spin-off, Bloom Biorenewables, in an effort to get them into the market.
Other contributors
University of Applied Sciences and Arts Western Switzerland
EPFL Institute of Materials
EPFL Valais-Wallis
The University of Manchester
Reference
Lorenz P. Manker, Maxime A. Hedou, Clement Broggi, Marie J. Jones, Kristoffer Kortsen, Kalaiyarasi Puvanenthiran, Yildiz Kupper, Holger Frauenrath, François Marechal, Veronique Michaud, Roger Marti, Michael P. Shaver, Jeremy S. Luterbacher. Performance polyamides built on a sustainable carbohydrate core. Nature Sustainability 13 March 2024. DOI: 10.1038/s41893-024-01298-7
The dyed and natural polyamide fibers after extrusion
Highly precise extrusion of 3D-printing filament
The polyamide is tough and flexible allowing it to be twisted and plied without breaking
Performance polyamides built on a sustainable carbohydrate core
ARTICLE PUBLICATION DATE
13-Mar-2024
KIMM finds solution to medical waste problem, which has become a major national issue
Through business support program, KIMM develops medical waste sterilization technology that can be applied to hospitals.
NATIONAL RESEARCH COUNCIL OF SCIENCE & TECHNOLOGY
IMAGE:
MEDICAL WASTE TREATMENT SYSTEM CAPABLE OF PROCESSING 100 KILOGRAMS OF MEDICAL WASTE PER HOUR, DEMONSTRATED AT THE CHUNGNAM NATIONAL UNIVERSITY HOSPITAL
CREDIT: KOREA INSTITUTE OF MACHINERY AND MATERIALS (KIMM)
A medical waste treatment system, which is capable of 99.9999 percent sterilization by using high-temperature and high-pressure steam, has been developed for the first time in the country.
The Korea Institute of Machinery and Materials (President Seog-Hyeon Ryu, hereinafter referred to as KIMM), an institute under the jurisdiction of the Ministry of Science and ICT, has succeeded in developing an on-site-disposal type medical waste sterilization system that can help to resolve the problem caused by medical waste, which has become a national and social issue as the volume of medical waste continues to increase every year. This project was launched as a basic business support program of the KIMM and was expanded into a demonstration project of Daejeon Metropolitan City. Then, in collaboration with VITALS Co., Ltd., a technology transfer corporation, the medical waste treatment system was developed as a finished product capable of processing more than 100 kilograms of medical waste per hour, and was demonstrated at the Chungnam National University Hospital.
Moreover, the installation and use of this product have been approved by the Geumgang Basin Environmental Office of the Ministry of Environment. All certification-related work for the installation and operation of this product at the Chungnam National University Hospital has been completed, including the passage of an installation test for efficiency and stability conducted by the Korea Testing Laboratory.
Through collaboration with VITALS Co., Ltd., a corporation specializing in inhalation toxicity systems, the research team led by Principal Researcher Bangwoo Han of the Department of Urban Environment Research of the KIMM’s Eco-Friendly Energy Research Division developed a high-temperature, high-pressure steam sterilization-type medical waste treatment system by using a high-temperature antimicrobial technology capable of processing biologically hazardous substances such as virus and bacteria with high efficiency. After pulverizing medical waste into small pieces so that high-temperature steam can penetrate deep into the interior of the medical waste, steam was then compressed in order to raise the boiling point of the saturated steam to over 100 degrees Celsius, thereby further improving the sterilization effect of the steam.
Meanwhile, in the case of the high-pressure steam sterilization method, it is vitally important to allow the airtight, high-temperature and high-pressure steam to penetrate deep into the medical waste. Therefore, the research team aimed to improve the sterilization effect of medical waste by increasing the contact efficiency between the pulverized medical waste and the aerosolized steam.
By using this technology, the research team succeeded in processing medical waste at a temperature of 138 degrees Celsius for 10 minutes or at 145 degrees Celsius for more than five (5) minutes, which is the world’s highest level. By doing so, the research team achieved a sterilization performance of 99.9999 percent targeting biological indicator bacteria at five (5) different locations within the sterilization chamber. This technology received certification as an NET (New Excellent Technology) in 2023.
Until now, medical waste has been sterilized by heating the exposed moisture using microwaves. However, this method requires caution because workers are likely to be exposed to electromagnetic waves and the entrance of foreign substances such as metals may lead to accidents.
In Korea, medical waste is mostly processed at exclusive medical waste incinerators and must be discharged in strict isolation from general waste. Hence, professional efforts are required to prevent the risk of infection during the transportation and incineration of medical waste, which requires a loss of cost and manpower.
If medical waste is processed directly at hospitals and converted into general waste by applying the newly developed technology, this can help to eliminate the risk of infection during the loading and transportation processes and significantly reduce waste disposal costs. By processing 30 percent of medical waste generated annually, hospitals can save costs worth KRW 71.8 billion. Moreover, it can significantly contribute to the ESG (environmental, social, and governance) management of hospitals by reducing the amount of incinerated waste and shortening the transportation distance of medical waste.
[*Allbaro System (statistical data from 2021): Unit cost of treatment for each type of waste for the calculation of performance guarantee insurance money for abandoned wastes (Ministry of Environment Public Notification No. 2021-259, amended on December 3, 2021). Amount of medical waste generated on an annual basis: 217,915 tons; Medical waste: KRW 1,397 per ton; General waste from business sites subject to incineration: KRW 299 per ton]
As the size and structure of the installation space varies for each hospital, installing a standardized commercial equipment can be a challenge. However, during the demonstration process at the Chungnam National University Hospital, the new system was developed in a way that allows the size and arrangement thereof to be easily adjusted depending on the installation site. Therefore, it can be highly advantageous in terms of on-site applicability.
Principal Researcher Bangwoo Han of the KIMM was quoted as saying, “The high-temperature, high-pressure steam sterilization technology for medical waste involves the eradication of almost all infectious bacteria in a completely sealed environment. Therefore, close cooperation with participating companies that have the capacity to develop airtight chamber technology is very important in materializing this technology.” He added, “We will make all-out efforts to expand this technology to the sterilization treatment of infected animal carcasses in the future.”
President Seog-Hyeon Ryu of the KIMM was quoted as saying, “The latest research outcome is significantly meaningful in that it shows the important role played by government-contributed research institutes in resolving national challenges. The latest technology, which has been developed through the KIMM’s business support program, has been expanded to a demonstration project through cooperation among the industry, academia, research institutes, and the government of Daejeon Metropolitan City.” President Ryu added, “We will continue to proactively support these regional projects and strive to develop technologies that contribute to the health and safety of the public.”
Waste that has been pulverized and sterilized
Medical waste treatment system capable of processing 100 kilograms of medical waste per hour, demonstrated at the Chungnam National University Hospital
CREDIT
Korea Institute of Machinery and Materials (KIMM)
Meanwhile, this research was conducted with the support of the project for the “development of ultra-high performance infectious waste treatment system capable of eliminating 99.9999 percent of viruses in response to the post-coronavirus era,” one of the basic business support programs of the KIMM, as well as the project for the “demonstration and development of a safety design convergence-type high-pressure steam sterilization system for on-site treatment of medical waste,” part of Daejeon Metropolitan City’s “Daejeon-type New Convergence Industry Creation Special Zone Technology Demonstration Project.”
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The Korea Institute of Machinery and Materials (KIMM) is a non-profit government-funded research institute under the Ministry of Science and ICT. Since its foundation in 1976, KIMM is contributing to economic growth of the nation by performing R&D on key technologies in machinery and materials, conducting reliability test evaluation, and commercializing the developed products and technologies.
This research was conducted with the support of the project for the “development of ultra-high performance infectious waste treatment system capable of eliminating 99.9999 percent of viruses in response to the post-coronavirus era,” one of the basic business support programs of the KIMM, as well as the project for the “demonstration and development of a safety design convergence-type high-pressure steam sterilization system for on-site treatment of medical waste,” part of Daejeon Metropolitan City’s “Daejeon-type New Convergence Industry Creation Special Zone Technology Demonstration Project.”
“Find pearls in the soil” unveiling the magic of hydrogen production from municipal sewage
Professor Kangwoo Cho and PhD candidate Jiseon Kim from the Division of Environmental Science & Engineering at Pohang University of Science and Technology (POSTECH) collaborated with the Korea Institute of Science and Technology (KIST) to devise a novel catalyst aimed at enhancing the efficiency of reactions using contaminated municipal sewage to produce hydrogen—a green energy source. Their research recently featured in the international journal Advanced Functional Materials.
With the growing environmental concerns of pollution associated with fossil fuel, hydrogen has garnered increased interest. Water electrolysis technology is a sustainable process that leverages Earth's abundant water to produce hydrogen. However, the concurrent oxygen evolution reaction during hydrogen production is notably slow, resulting in a considerably low energy conversion efficiency.
Lately, the academic community has been tackling this issue by integrating the urea oxidation reaction with the hydrogen generation reaction. Urea, a pollutant found in urine, releases a significant amount of energy during its oxidation process, offering a potential means to enhance both the efficiency of hydrogen generation and the purification of toilet wastewater. Ultimately, it is necessary to find a catalyst that can effectively drive the urea oxidation reaction, thereby amplifying the efficiency of both hydrogen generation and wastewater treatment.
In pursuit of increased efficiency in the urea oxidation reaction, the team created a catalyst known as nickel-iron-oxalate (O-NFF). This catalyst combines iron (Fe) and oxalate on nickel (Ni) metal, resulting in an expansive surface area characterized by nanometer-sized particles in fragment form. This unique property enables the catalyst to adsorb more reactants, facilitating an accelerated urea oxidation reaction.
In experiments, the O-NFF catalyst devised by the team successfully lowered the voltage required for hydrogen generation to 1.47 V RHE (at 0.5 A/cm2) and exhibited a high reaction rate even when tested in a mixed solution of potassium hydroxide (1 M) and urea (0.33 M) with a Tafel slope of 12.1 mV/dec. The researchers further validated the catalyst's efficacy by confirming its promotion of the urea oxidation reaction through photoelectron/X-ray absorption spectroscopy using a radiation photo accelerator.
Professor Kangwoo Cho who led the research stated, "We have developed a catalyst capable of purifying municipal sewage while simultaneously enhancing the efficiency of hydrogen production, a green energy source.” He added, “We anticipate that O-NFF catalysts, synthesized from metals and organics, will contribute to the improved efficiency of industrial electrolysis hydrogen production."
The research was sponsored by the Mid-Career Researcher Program and the Hydrogen Source Technology Development Program of the National Research Foundation of Korea, and the National Supercomputing Center.
