Sep
28
Research Shows A New Thermoelectric Twice As Productive
September 28, 2023 | Leave a Comment
Researchers at the Vienna University of Technology discovered excellent thermoelectric properties of nickel-gold alloys. These can be used to efficiently convert heat into electrical energy.
The researchers have published their results in the journal Science Advances.
Thermoelectrics enable the direct conversion of heat into electrical energy – and vice versa. This makes them interesting for a range of technological applications. In the search for thermoelectric materials with the best possible properties, a research team at TU Wien investigated various metallic alloys. A mixture of nickel and gold proved particularly promising.
Using thermoelectrics to generate electricity is nothing new. Since the middle of the 20th century, they have been used to generate electrical energy in space exploration, but thermoelectrics are also used in everyday applications such as portable refrigerators. Moreover, they could also be used in industrial environments to convert waste heat into green electricity, to name just one of the potential applications.
How thermoelectricity works
The thermoelectric effect is based on the movement of charged particles that migrate from the hotter to the colder side of a material. This results in an electrical voltage – the so-called thermoelectric voltage – which counteracts the thermally excited movement of the charge carriers. The ratio of the built-up thermoelectric voltage and the temperature difference defines the Seebeck coefficient, named after the German physicist Thomas Johann Seebeck, which is an important parameter for the thermoelectric performance of a material. The important requirement here is that there is an imbalance between positive and negative charges, as they compensate each other.
“Although Seebeck discovered the thermoelectric effect in common metals more than 200 years ago, nowadays metals are hardly considered as thermoelectric materials because they usually have a very low Seebeck coefficient,” explained Fabian Garmroudi, first author of the study. On the one hand, metals such as copper, silver or gold have extremely high electrical conductivity; on the other hand, their Seebeck coefficient is vanishingly small in most cases.
Nickel-gold alloys with outstanding properties
Physicists from the Institute of Solid State Physics (TU Wien) have now succeeded in finding metallic alloys with high conductivity and an exceptionally large Seebeck coefficient. Mixing the magnetic metal nickel with the noble metal gold radically changes the electronic properties. As soon as the yellowish color of gold disappears when about 10 % nickel is added, the thermoelectric performance increases rapidly. The physical origin for the enhanced Seebeck effect is rooted in the energy-dependent scattering behavior of the electrons – an effect fundamentally different from semiconducting thermoelectrics. Due to the particular electronic properties of the nickel atoms, positive charges are scattered more strongly than negative charges, resulting in the desired imbalance and hence a high thermoelectric voltage.
“Imagine a race between two runners, where one person runs on a free track, but the other person has to get through many obstacles. Of course, the person on the free track advances faster than the opponent, who has to slow down and change direction much more often,” compared Andrej Pustogow, senior author of the study, the flow of electrons in metallic thermoelectrics. In the alloys studied here, the positive charges are strongly scattered by the nickel electrons, while the negative charges can move practically undisturbed.
Record breaking material
The combination of extremely high electrical conductivity and simultaneously a high Seebeck coefficient leads to record thermoelectric power factor values in nickel-gold alloys, which exceed those of conventional semiconductors by far. “With the same geometry and fixed temperature gradient, many times more electrical power could be generated than in any other known material,” explained Fabian Garmroudi. In addition, the high power density may enable everyday applications in the large-scale sector in the future. “Already with the current performance, smartwatches, for instance, could already be charged autonomously using the wearer’s body heat,” Andrej Pustogow gave as an example.
Nickel-gold is just the beginning
“Even though gold is an expensive element, our work represents a proof of concept. We were able to show that not only semiconductors, but also metals can exhibit good thermoelectric properties that make them relevant for diverse applications. Metallic alloys have various advantages over semiconductors, especially in the manufacturing process of a thermoelectric generator,” explained Michael Parzer, one of the lead authors of the study.
The fact that the researchers were able to experimentally show that nickel-gold alloys are extremely good thermoelectrics is no coincidence. “Even before starting our experimental work, we calculated with theoretical models which alloys were most suitable,” revealed Michael Parzer. Currently, the group is also investigating other promising candidates that do not require the expensive element gold.
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Two takeaways from this news are first a massive improvement in productivity is at hand. Then there is the record power factor in a scenario that is different from the semiconductor sets now making some market progress.
Most encouraging is that work is underway to find and prove up much less costly metal alloys to build thermoelectric units.
Mostly an “out of sight” harvesting system, thermoelectric has immense potential. The amount of wasted heat is simply a stunning number in all applications. The idea that the temperature variation from ambient air to skin temperature could power small personal electronics is a head turning idea.
Sep
27
Highly Efficient Electrocatalyst Enhances Water Splitting
September 27, 2023 | Leave a Comment
A City University of Hong Kong research team achieved a groundbreaking advancement in nanomaterials by successfully developing a highly efficient electrocatalyst. The catalyst can enhance the generation of hydrogen significantly through electrochemical water splitting.
The discovery, published in the journal Nature, centers on developing a highly efficient electrocatalyst that can enhance hydrogen generation through electrocatalytic water splitting. The paper is titled “Phase-dependent growth of Pt on MoS2 for highly efficient H2 evolution.”
Hydrogen bubbles produced and released from the s-Pt/1T′-MoS2 electrode. Image Credit:City University of Hong Kong. To see the one minute video click this link.
Professor Zhang Hua, Herman Hu Chair Professor of Nanomaterials at CityU, who is spearheading the research said, “Hydrogen generated by electrocatalytic water splitting is regarded as one of the most promising clean energies for replacing fossil fuels in the near future, reducing environmental pollution and the greenhouse effect.”
Professor Zhang’s collaborators include Professor Anthony R. J. Kucernak from the Department of Chemistry at Imperial College London and researchers from universities and research institutes in Hong Kong, mainland China, Singapore and the UK.
The critical development in the CityU-led research is establishing novel catalysts by using the transition-metal dichalcogenide (TMD) nanosheets as supports, enabling superior efficiency and high stability during the electrocatalytic hydrogen evolution reaction (HER), a vital step in electrocatalytic water-splitting, also known as the water electrolysis technique, for hydrogen production.
The team has been exploring how to enhance the performance of the HER process by engineering the crystal phase of nanomaterials for several years. Although TMD nanosheets with unconventional crystal phases possess great potential to be used as catalyst supports, fabricating such sheets pure enough for HER is far from straightforward.
But in this research, Professor Zhang’s team has developed a new method to prepare unconventional-phase TMD nanosheets with high phase-purity and quality. Furthermore, they have investigated the crystal phase-dependent growth of noble metals on the TMD nanosheet supports.
Technically speaking, they found that the 2H-phase template facilitates the epitaxial growth of Pt nanoparticles, whereas the 1T′-phase template supports single-atomically dispersed Pt atoms (s-Pt). The synthesized s-Pt/1T′-MoS2 serves as a highly efficient catalyst for HER and can work for 500 hours in the water electrolyser, demonstrating that 1T′-TMD nanosheets could be effective supports for catalysts.
Dr Shi Zhenyu, a postdoctoral researcher in CityU’s Department of Chemistry and the first author of the paper noted, “We will develop more efficient catalysts based on this finding and explore their applications in various catalytic reactions.”
These findings expand the scope of phase engineering in nanomaterials, paving the way for the design and synthesis of highly efficient catalysts, contributing to cleaner energies and more sustainable development.
***
This looks quite promising. While still relying on platinum there might be a reduction in the amount needed and improving the lifespan of the electrolyser.
This is news that’s sure to energize the hydrogen enthusiasts.
Never-the-less, as the effort to come up with low cost ways to split water, platinum can only work if it lasts a really (really) long time. That’s where this team’s work might bear real relevancy.
Enthusiasts are also going to have to work on the cost of the energy. The news and commentary suggests the energy will come from “excess production”. But the plant’s costs and maintenance are going to be need paid for. Excess implies they will running, not standing by without wear and ageing.
Meanwhile, lets hope the breakthrough value in this also applies to fuel cell production.
Sep
26
Better Hydrogen Production Catalyst For Handling Oxygen
September 26, 2023 | Leave a Comment
The study paper was published in the Journal of Power Sources. The study was co-authored by Dr. Chaekyung Baik, a post-doctoral researcher at Korea Institute of Science and Technology (KIST).
Proton exchange membrane water electrolyzers converts surplus electric energy into transportable hydrogen energy as a clean energy solution. However, slow oxygen evolution reaction rates and high loading levels of expensive metal oxide catalysts limit its practical feasibility. The GIST catalyst also shows high catalytic activity and long-term stability in prolonged single cell operation.
The energy demands of the world are ever increasing. In the quest for clean and eco-friendly energy solutions, transportable hydrogen energy offers considerable promise. In this regard, proton exchange membrane water electrolyzers (PEMWEs) that convert excess electric energy into transportable hydrogen energy through water electrolysis have garnered remarkable interest.
However, their wide scale deployment for hydrogen production remains limited due to slow rates of oxygen evolution reaction (OER) – an important component of electrolysis – and high loading levels of expensive metal oxide catalysts, such as iridium (Ir) and ruthenium oxides, in electrodes. Therefore, developing cost-effective and high-performance OER catalysts is necessary for the widespread application of PEMWEs.
Recently, a team of researchers from Korea and USA, led by Professor Chanho Pak from Gwangju Institute of Science and Technology in Korea, has developed a novel mesoporous tantalum oxide (Ta2O5)-supported iridium nanostructure catalyst via a modified formic acid reduction method that achieves efficient PEM water electrolysis.
Prof. Pak explained, “The electron-rich Ir nanostructure was uniformly dispersed on the stable mesoporous Ta2O5 support prepared via a soft-template method combined with an ethylenediamine encircling process, which effectively decreased the amount of Ir in a single PEMWE cell to 0.3 mg cm-2. Importantly, the innovative Ir/Ta2O5 catalyst design not only improved the utilization of Ir but also facilitated higher electrical conductivity and a large electrochemically active surface area.
Additionally, X-ray photoelectron and X-ray absorption spectroscopies revealed strong metal-support interaction between Ir and Ta, while density functional theory calculations indicated a charge transfer from Ta to Ir, which induced the strong binding of adsorbates, such as O and OH, and maintained Ir (III) ratio in the oxidative OER process. This, in turn, led to the enhanced activity of Ir/Ta2O5, with a lower overpotential of 0.385 V compared to a 0.48 V for IrO2.
The team also demonstrated high OER activity of the catalyst experimentally, observing an overpotential of 288 ± 3.9 mV at 10 mA cm-2 and a mass activity of 876.1 ± 125.1 A g-1 of Ir at 1.55 V, significantly higher than the corresponding values for Ir Black. In effect, Ir/Ta2O5 exhibited excellent OER activity and stability, as further confirmed through membrane electrode assembly single cell operation of over 120 hours.
The proposed technology offers the dual benefit of reduced Ir loading levels and an enhanced OER efficiency. “The improved OER efficiency complements the cost-effectiveness of the PEMWE process, enhancing its overall performance. This advancement has the potential to revolutionize the commercialization of PEMWEs, accelerating its adoption as a primary method for hydrogen production,” speculated an optimistic Prof. Pak.
***
This looks like real progress on the water splitting effort. And by any means a 120 hour run without a productivity drop off is worthwhile news by itself.
But still, this work is on producing pure hydrogen.
One day someone will write a post about just what a straight hydrogen economy might be actually like. Something in gaseous form that ignites at 4% to 96% and is nearly impossible to keep stored for transport without it simply slipping out of the container. Sounds like quite a challenge.
Widely observant folks do understand the mechanics of the positioning. To the hysterics and the media carbon is evil. One wonders how long they would last if the was no carbon in their lives at all.
Perhaps the realization that hydrogen is best hooked up to some carbon for practical use will gain traction one day. Which means this team’s work is useful, important, and a step into a better future.
Sep
21
New Catalyst Found For Electrocatalytic CO2 Recycling
September 21, 2023 | Leave a Comment
The work was made available and published in the journal Science of the Total Environment.
Carbon dioxide can be electrocatalytically reduced to useful resources using conventional catalysts such as gold or lead supported on conductive carbon. However, the high pH environment near electrodes often degrades the catalyst support, rendering them ineffective.
Process Diagram For Recycling CO2 To Useful Chemicals. Image Credit: Tokyo University of Science. For a larger version of the image and more information click the press release link.
One approach to CO2 conversion is through electrocatalytic reduction. This process utilizes conventional catalysts, such as lead, silver, tin, copper, gold etc. supported on conductive carbon as electrode material for selectively CO2 reduction. However, the electrode is often exposed to a high pH environment of the electrolyte during electrocatalysis, which can degrade the catalyst support and is a cause of major concern.
To address this challenge, a team of researchers, led by Mr. Kai Takagi and Prof. Chiaki Terashima from Graduate School of Science and Technology and Research Institute for Science and Technology at Tokyo University of Science (TUS) in Japan, has recently developed a catalyst support based on titanium dioxide (TiO2) powder, a compound commonly used in sunscreen, paints, coatings, toothpaste, plastics, paper, pharmaceuticals, and food coloring, as an alternative to carbon for facilitating effective CO2 reduction.
The researchers first carried out surface treatment using safe and inexpensive in-liquid plasma to improve the electrochemical properties of TiO2.
Prof. Terashima noted, “The in-liquid plasma-treated TiO2 maintained its particle shape and crystal structure. Additionally, elemental analysis and evaluation of the interfacial bonding state and electrochemical properties of TiO2 revealed that the redox peaks corresponding to Ti4+ and Ti3+ derived from TiO2 disappeared and the hydrogen overvoltage decreased.”
These observations led the team to conclude that tungsten coating or doping occurred on some portions of the reduced TiO2 surface.
The researchers then used the TiO2 as a carrier and loaded it with silver nanoparticles (AgNPs), which act as catalysts, to develop a gas diffusion electrode for CO2 reduction. While untreated TiO2 exhibited high selectivity for CO2 and carbon black, in-liquid plasma-treated TiO2 with 40 wt% AgNP loading demonstrated increased hydrogen production and enhanced catalytic performance.
Given that a suitable ratio of hydrogen to carbon monoxide is important for effective CO2 reduction, the presented technology, thus, has tremendous potential for converting CO2 to useful byproducts, such as syngas, which is considered a clean fuel with very high industrial value.
Additionally, the electrocatalytic reduction of CO2 can be integrated with renewable energy sources, such as solar panels or wind power, for sustainable and environmentally friendly CO2 conversion. Therefore, this work is a significant step towards efficiently tackling greenhouse gas emissions and fighting climate change.
Prof. Terashima concluded with, “Hopefully, the present study will promote research on technologies for carbon neutrality and carbon recycling, in alignment with the United Nations Sustainable Development Goals 7, 12, and 13 on affordable and clean energy, responsible consumption and production, and climate action, respectively. These, in turn, will open doors to the realization of a carbon-neutral and sustainable future.”
***
Recycling CO2 has to be part of humanity getting into a current carbon cycle with the planet. Without CO2 recycling the balance needed will not likely be achieved. The idea of 10 billion people using carbon sources for fueling an energy rich existence seems to be a major mess even if the sootiness is minimized and the secondary pollution chemicals are minimized.
But if carbon resources are recycled there is little limit to how high standards of living can get for many billions of people. Carbon itself is a great store of energy and can store immense amounts of hydrogen. It would be the natural thing to do as its just what nature has been doing for hundreds of millions of years.
Sep
20
New Record Efficiency For Tandem Silicon Perovskite Cells
September 20, 2023 | Leave a Comment
Dr Artiom Magomedov, a researcher at Kaunas University of Technology, Lithuania remarked, “There is a kind of race going on among research teams around the world. In the last year, the solar cell efficiency record has been broken three or four times, it’s just the publication of scientific papers that takes time.”
According to Dr Magomedov, the co-author of a recent paper published in the scientific journal Science, the most current published record for tandem perovskite solar cells is 32.5 percent. The paper reports on the improvements in silicon-perovskite tandem cells that have made this possible.
Dr Magomedov, a researcher at Kaunas University of Technology (KTU), Lithuania explained, “Tandem solar cells have more than ten layers, so it is technologically very challenging to ensure their smooth operation. The development of such solar cells involves a large number of researchers. For example, our research team is responsible for one of the layers, which is made of hole-transporting materials.”
Back in 2018, a group of KTU chemists synthesized a material that forms a molecule-thick layer, also known as a monolayer, which evenly covers a variety of surfaces. Several highly efficient solar cells have already been developed using this material. According to Dr Magomedov, one of the authors of the invention, the KTU innovation has become a commonplace among scientists developing the latest solar technologies.
The mass-production of next generation solar cells will have to wait
The recent scientific article is Dr Magomedov’s second co-authored publication in Science, and is serving as a follow-up to the previous one, proposing a solution to the challenge at hand.
“Although our materials help achieve the highest efficiency, it is difficult to form another layer on top. After our previous paper in Science, we received a lot of attention and comments about how our materials act in different contexts. In the current paper, we show one way to address the problems,” said Dr Magomedov.
More details about the improvement proposed by the KTU research team, which, together with the solutions developed by other scientists around the world, has led to the construction of an ultra-high-efficiency tandem solar cell, can be found in the scientific article. The ultra-high efficiency tandem solar cell was constructed by a research group led by Prof Steve Albrecht from Helmholtz-Zentrum Berlin, in Germany.
Silicon solar cells have a peak potential efficiency of only 29%; the world needs more and more alternative energy sources due to the climate change crisis. Tandem solar cells consist of two types of photoactive layers – a perovskite solar element is placed on top of silicon. The silicon layer collects infrared light, while the perovskite collects blue light from the visible spectrum, increasing the efficiency of the solar cell. However, according to Dr Magomedov, it will still take time for the new generation of solar cells to replace those in use today.
“In theory, electricity made by tandem solar cells would be cheaper because the additional materials used are cheaper. However, in practice, the final commercial product does not exist, the technological processes are not ready for mass production. Moreover, the cell itself, which is only being developed in laboratories so far, also raises unanswered questions. For example, not all materials are suitable for mass production, which means that alternatives have to be found,” Magomedov explained.
One of the biggest challenges in the production of these cells so far, he says, is their stability. Solar cells are expected to last for 25 years, during which time they will lose 10% of their efficiency. However, testing over such a long period of time is difficult, so there is no definitive answer as to how the new generation of solar cells will wear out.
Lithuanian chemists – world experts in new materials for solar cells
The synthesis and analysis of chemical materials for solar technologies has been Dr Magomedov’s topic since the beginning of his undergraduate studies, when he joined a research group led by KTU Professor Vytautas Getautis. As the need for new materials for solar cells emerged, the talented chemists used their competences and established themselves in the niche that opened up, gaining international recognition.
“We are probably the most specialized research group in the world,” joked Dr Magomedov.
He said that good results are motivating, offer exciting prospects for collaboration and open up new research opportunities. It is great to contribute to a global scientific breakthrough. In addition, Dr Magomedov said, the development of solar technologies is a very topical issue in the context of today’s world, and the inventions can be widely applied.
“Broadly speaking, we are working with new electronics with a very wide range of applications. And of course, in the topic of solar technology itself, the solar energy storage and batteries issue is inevitably coming up,” noted Dr Magomedov.
Currently, a research group of KTU chemists led by Prof Getautis is involved in a project to develop a pilot production line for tandem silicon-perovskite solar cells, and is looking for ways to apply the developed materials to other technologies, such as light emitting diodes. In parallel, fundamental questions are also being explored, such as why semiconductors developed in the lab work the way they do.
***
It is always a great benefit when one of the principle people in a research effort includes in the interview a situational perspective. Yes, the new world record is solid news, and the tech is so new and unique that no manufacturing looks to be attempted just yet and much remains to be done before a look at process engineering to build cells.
Refreshing, to say mildly, just how a few sentences can put a technology in the proper frame of mind for the observer. For that, A Big Thank You!
Meanwhile, its likely that materials research is underway to find the materials to give manufacturing at scale a high probability.
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