Energy & Green Technology Updates vol.75
November 26th 2024
Check out latest research updates in the field
TL;DR
- Advancing solar-powered hydrogen production
- Self-charging supercapacitors powered by solar energy
- Transforming industrial waste into energy storage solutions
- New technique identifies harmful salts in nuclear waste melters
- Lightweight, flexible, and radiation-resistant organic solar cells for space applications
Latest Research
Chemical and Valence Electron Structure of the Core and Shell of Sn(II)-Perovskite Oxide Nanoshells
by Gowri Krishnan, Shaun O’Donnell, Rachel Broughton, Jacob L. Jones, D. J. Osborn, Thomas D. Small, Theresa Block, Aylin Koldemir, Rainer Pöttgen, Gregory F. Metha, Paul A. Maggard, Gunther G. Andersson in The Journal of Physical Chemistry C
Another advance has been made by experts in nano-scale chemistry to propel further development of sustainable and efficient generation of hydrogen from water using solar power
In a new international collaborative study -- led by Flinders University with collaborators in South Australia, the US and Germany -- experts have identified a novel solar cell process to potentially use in future technologies for photocatalytic water splitting in green hydrogen production.
Combined with a catalyst -- developed by US research led by Professor Paul Maggard -- for water splitting, the study found the new class of kinetically stable 'core and shell Sn(II)-perovskite' oxide solar material could be a potential catalyst for the critical oxygen evolution reaction in producing pollution-free hydrogen energy in future. The results pave the way for further inroads into carbon-free 'green' hydrogen technologies using non-greenhouse-gas-emitting forms of power with high-performing, affordable electrolysis.
"This latest study is an important step forwards in understanding how these tin compounds can be stabilised and effective in water," says lead author Professor Gunther Andersson, from the Flinders Institute for Nanoscale Science and Technology at the College of Science and Engineering.
"Our reported material points to a novel chemical strategy for absorbing the broad energy range of sunlight and using it to drive fuel-producing reactions at its surfaces," adds Professor Paul Maggard, from the Department of Chemistry and Biochemistry at Baylor University.
Already these tin and oxygen compounds are used in a variety of applications, including catalysis, diagnostic imaging and therapeutic drugs. However, Sn(II) compounds are reactive with water and dioxygen, which can limit their technological applications.
Solar photovoltaic research around the world is focusing on developing cost-effective, high performance perovskite generation systems as an alternative to conventional existing silicon and other panels.
Low-emission hydrogen can be produced from water through electrolysis (when an electric current splits water into hydrogen and oxygen) or thermochemical water splitting, a process which also can be powered by concentrated solar power or waste heat from nuclear power reactors.
Hydrogen can be produced from diverse resources including fossil fuels such as natural gas and biological biomass, but the environmental impact and energy efficiency of hydrogen depends on how it is produced.
Solar-driven processes use light as an agent for hydrogen production and is a potential alternative for generating industrial-scale hydrogen.
by Damin Lee, Nilanka M. Keppetipola, Dong Hwan Kim, Jong Wook Roh, Ludmila Cojocaru, Thierry Toupance, Jeongmin Kim in Energy
Jeongmin Kim, Senior Researcher at DGIST (President Kunwoo Lee), in joint research with Damin Lee, Researcher at the RLRC of Kyungpook National University (President Young-woo Heo), has developed a high-performance self-charging energy storage device capable of efficiently storing solar energy. The research team has dramatically improved the performance of existing supercapacitor devices by utilizing transition metal-based electrode materials and proposed a new energy storage technology that combines supercapacitors with solar cells.
The research team designed the electrodes using a nickel-based carbonate and hydroxide composite material and maximized the conductivity and stability of the electrodes by adding transition metal ions such as Mn, Co, Cu, Fe, and Zn. This technology has greatly improved the performance of energy storage devices, demonstrating significant advancements in energy density, power density, and charge and discharge stability.
Particularly, the energy density achieved in this study is 35.5 Wh kg⁻¹, which is significantly higher than the energy storage per unit weight in previous studies (5-20 Wh kg⁻¹). The power density is 2555.6 W kg⁻¹, significantly exceeding the values from previous studies (- 1000 W kg⁻¹), demonstrating the ability to release higher power rapidly, enabling immediate energy supply even for high-power devices. Additionally, the performance showed minimal degradation during repeated charge and discharge cycles, confirming the long-term usability of the device.
Furthermore, the research team developed an energy storage device that combines silicon solar cells with supercapacitors, creating a system capable of storing solar energy and utilizing it in real time. This system achieved an energy storage efficiency of 63% and an overall efficiency of 5.17%, effectively validating the potential for commercializing the self-charging energy storage device.
Jeongmin Kim, Senior Researcher at the Nanotechnology Division of DGIST, states, "This study is a significant achievement, as it marks the development of Korea's first self-charging energy storage device combining supercapacitors with solar cells. By utilizing transition metal-based composite materials, we have overcome the limitations of energy storage devices and presented a sustainable energy solution." Damin Lee, a researcher at the RLRC of Kyungpook National University, stated, "We will continue to conduct follow-up research to further improve the efficiency of the self-charging device and enhance its potential for commercialization."
Triphenylphosphine Oxide-Derived Anolyte for Application in Nonaqueous Redox Flow Battery
by Emily R. Mahoney, Maxime Boudjelel, Henry Shavel, Matthew D. Krzyaniak, Michael R. Wasielewski, Christian A. Malapit in Journal of the American Chemical Society
The batteries used in our phones, devices and even cars rely on metals like lithium and cobalt, sourced through intensive and invasive mining. As more products begin to depend on battery-based energy storage systems, shifting away from metal-based solutions will be critical to facilitating the green energy transition.
Now, a team at Northwestern University has transformed an organic industrial-scale waste product into an efficient storage agent for sustainable energy solutions that can one day be applied at much larger scales. While many iterations of these batteries, called redox flow batteries, are in production or being researched for grid-scale applications, using a waste molecule -- triphenylphosphine oxide (TPPO) -- marked a first in the field.
Thousands of tons of the well-known chemical byproduct are produced each year by many organic industrial synthesis processes -- including the production of some vitamins, among other things -- but it is rendered useless and must be carefully discarded following production.
In a paper, a "one-pot" reaction allows chemists to turn TPPO into a usable product with powerful potential to store energy, opening the door for viability of waste-derived organic redox flow batteries, a long-imagined battery type.
"Battery research has traditionally been dominated by engineers and materials scientists," said Northwestern chemist and lead author Christian Malapit. "Synthetic chemists can contribute to the field by molecularly engineering an organic waste product into an energy-storing molecule. Our discovery showcases the potential of transforming waste compounds into valuable resources, offering a sustainable pathway for innovation in battery technology."
Malapit is an assistant professor in the department of chemistry at Northwestern's Weinberg College of Arts and Sciences.
A small part of the battery market at present, the market for redox flow batteries is expected to rise by 15% between 2023 and 2030 to reach a value of 700 million euros worldwide. Unlike lithium and other solid-state batteries which store energy in electrodes, redox flow batteries use a chemical reaction to pump energy back and forth between electrolytes, where their energy is stored. Though not as efficient at energy storage, redox flow batteries are thought to be much better solutions for energy storage at a grid scale.
"Not only can an organic molecule be used, but it can also achieve high-energy density -- getting closer to its metal-based competitors -- along with high stability," said Emily Mahoney, a Ph.D. candidate in the Malapit lab and the paper's first author. "These two parameters are traditionally challenging to optimize together, so being able to show this for a molecule that is waste-derived is particularly exciting."
To achieve both energy density and stability, the team needed to identify a strategy that allowed electrons to pack tightly together in the solution without losing storage capacity over time. They looked to the past and found a paper from 1968 describing the electrochemistry of phosphine oxides and, according to Mahoney, "ran with it."
Then, to evaluate the molecule's resilience as a potential energy-storage agent, the team ran tests using static electrochemical charge and discharge experiments similar to the process of charging a battery, using the battery, and then charging it again, over and over. After 350 cycles, the battery maintained remarkable health, losing negligible capacity over time.
"This is the first instance of utilizing phosphine oxides -- a functional group in organic chemistry -- as the redox-active component in battery research," Malapit said. "Traditionally, reduced phosphine oxides are highly unstable. Our molecular engineering approach addresses this instability, paving the way for their application in energy storage."
In the meantime, the group hopes other researchers will pick up the charge and begin to work with TPPO to further optimize and improve its potential.
by John M. Bussey, Ian A. Wells, Natalie J. Smith-Gray, John S. McCloy in Measurement
A new way to identify salts in nuclear waste melters could help improve clean-up technology, including at the Hanford Site, one of the largest, most complex nuclear waste clean-up sites in the world.
Washington State University researchers used two detectors to find thin layers of sulfate, chloride and fluoride salts during vitrification, a nuclear waste storage process that involves converting the waste into glass. The formation of salts can be problematic for waste processing and storage.
"We were able to demonstrate a technique to see when the salts are forming," said John Bussey, a WSU undergraduate who is one of the paper's lead authors. "By doing that, the melters could be monitored to know if we should change what is being put in the melt."
Vitrification entails putting the nuclear waste into large melters that are then heated to high temperatures. The resulting glass is then poured into cylinders and solidified for long-term safe storage.
The U.S. Department of Energy is building a vitrification plant at the Hanford Site. Because Hanford was used to make plutonium for the very first nuclear bomb, the waste there is particularly complex, containing nearly all of the elements of the periodic table, said Bussey. A total of 55 million gallons of chemical and nuclear waste are stored in 177 tanks at the site.
In the processing of the nuclear waste, salts can form. They can be corrosive and ruin very expensive vitrification equipment. Furthermore, since they dissolve in water, salts in the final glass waste form could lead to leaks and contamination if the waste form becomes exposed to water during storage. The wide variety of waste components at Hanford makes salt formation more likely.
"Salt formation is very undesirable during the vitrification process," said Bussey.
With a system that was developed at Pacific Northwest National Laboratory and the Massachusetts Institute of Technology, the researchers used optical and electrical components to look at light between infrared and microwave wavelengths that are naturally emitted during the melting process. They looked at samples of glass melts that are similar to those found at the Hanford site. Using two types of detectors, they were able to study the thermal emissions of the samples as well as the change over time.
"The brightness is really interesting for identifying all of the melting, solidification and salt formation," said Ian Wells, co-lead author and a graduate student in the WSU School of Mechanical and Materials Engineering. "What is really unique about this is you don't have to add any additional lighting or additional systems -- Purely based on the heat that is coming off the melt, you are able to look at the brightness of one-pixel images, and you can tell what's happening."
The researchers were able to see when there's a large change in the melt. Whether because a salt is forming or if there's melting or solidification, there is also a sharp change in the intensity. The researchers compared different melts and were able to identify behavior indicative of salts.
"We can clearly identify what is happening based on that behavior," said Wells. "We were surprised by how sensitive a probe it was even with very small amounts of salt."
The system can discriminate between salt types. The sensors can also sense the salts remotely, without having to be dipped in the radioactive molten glass, thus avoiding additional challenges.
"This work takes this monitoring technology a good step of the way closer to being able to be used inside the vitrification plant," said Bussey. "This piece of equipment without too much modification could be put straight into the vitrification plant."
The researchers think the work has other potential applications in molten salt nuclear reactors or in different types of manufacturing processes, such as glass, epoxies or carbon fiber processing, in which manufacturers want to better understand phase changes and the formation of different compounds during those phases. They hope to next move from lab-scale testing to larger scale melt tests.
Radiation hardness of organic photovoltaics
by Yongxi Li, Karthik Kamaraj, Yogita Silori, Haonan Zhao, Claire Arneson, Bin Liu, Jennifer Ogilvie, Stephen R. Forrest in Joule
Radiation testing suggests that solar cells made from carbon-based, or organic, materials could outperform conventional silicon and gallium arsenide for generating electricity in the final frontier, a study from the University of Michigan suggests.
While previous research focused on how well organic solar cells converted light to electricity following radiation exposure, the new investigation also dug into what happens at the molecular level to cause drops in performance.
"Silicon semiconductors aren't stable in space because of proton irradiation coming from the sun," said Yongxi Li, first author of the study to be published in Joule and a U-M associate research scientist in electrical and computer engineering at the time of the research. "We tested organic photovoltaics with protons because they are considered the most damaging particles in space for electronic materials."
Space missions often land on gallium arsenide for its high efficiency and resistance to damage from protons, but it's expensive and, like silicon, is relatively heavy and inflexible. In contrast, organic solar cells can be flexible and are much lighter. This study is among those exploring the reliability of organics, as space missions tend to use highly trusted materials.
Organic solar cells made with small molecules didn't seem to have any trouble with protons -- they showed no damage after three years worth of radiation. In contrast, those made with polymers -- more complex molecules with branching structures -- lost half of their efficiency.
"We found that protons cleave some of the side chains, and that leaves an electron trap that degrades solar cell performance," said Stephen Forrest, the Peter A. Franken Distinguished University Professor of Engineering at U-M, and lead corresponding author of the study.
These traps grab onto electrons freed by light hitting the cell, preventing them from flowing to the electrodes that harvest the electricity.
"You can heal this by thermal annealing, or heating the solar cell. But we might find ways to fill the traps with other atoms, eliminating this problem," Forrest said.
It's plausible that sun-facing solar cells could essentially self-heal at temperatures of 100°C (212°F) -- this warmth is enough to repair the bonds in the lab. But questions remain: for instance, will that repair still take place in the vacuum of space? Is the healing reliable enough for long missions? It may be more straightforward to design the material so that the performance-killing electron traps never appear.
Li intends to explore both avenues further as an incoming associate professor of advanced materials and manufacturing at Nanjing University in China.
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