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Energy Storage Using Oxygen to Boost Battery Performance
Researchers have presented a novel electrode material for advanced energy storage device that is directly charged with oxygen from the air. Professor Jeung Ku Kang’s team synthesized and preserved the sub-nanometric particles of atomic cluster sizes at high mass loadings within metal-organic frameworks (MOF) by controlling the behavior of reactants at the molecular level. This new strategy ensures high performance for lithium-oxygen batteries, acclaimed as a next-generation energy storage technology and widely used in electric vehicles. Lithium-oxygen batteries in principle can generate ten times higher energy densities than conventional lithium-ion batteries, but they suffer from very poor cyclability. One of the methods to improve cycle stability is to reduce the overpotential of electrocatalysts in cathode electrodes. When the size of an electrocatalyst material is reduced to the atomic level, the increased surface energy leads to increased activity while significantly accelerating the material’s agglomeration. As a solution to this challenge, Professor Kang from the Department of Materials Science and Engineering aimed to maintain the improved activity by stabilizing atomic-scale sized electrocatalysts into the sub-nanometric spaces. This is a novel strategy for simultaneously producing and stabilizing atomic-level electrocatalysts within metal-organic frameworks (MOFs). Metal-organic frameworks continuously assemble metal ions and organic linkers. The team controlled hydrogen affinities between water molecules to separate them and transfer the isolated water molecules one by one through the sub-nanometric pores of MOFs. The transferred water molecules reacted with cobalt ions to form di-nuclear cobalt hydroxide under precisely controlled synthetic conditions, then the atomic-level cobalt hydroxide is stabilized inside the sub-nanometric pores. The di-nuclear cobalt hydroxide that is stabilized in the sub-nanometric pores of metal-organic frameworks (MOFs) reduced the overpotential by 63.9% and showed ten-fold improvements in the life cycle. Professor Kang said, “Simultaneously generating and stabilizing atomic-level electrocatalysts within MOFs can diversify materials according to numerous combinations of metal and organic linkers. It can expand not only the development of electrocatalysts, but also various research fields such as photocatalysts, medicine, the environment, and petrochemicals.” This study was reported in Advanced Science (Title: Autogenous Production and Stabilization of Highly Loaded Sub-Nanometric Particles within Multishell Hollow Metal-Organic Frameworks and Their Utilization for High Performance in Li-O2 Batteries). This research was mainly supported by the Global Frontier R&D Program of the Ministry of Science, ICT & Planning (Grant No. 2013M3A6B1078884) funded by the Ministry of Science, ICT & Future Planning, and the National Research Foundation of Korea (Grant No. 2019M3E6A1104196). Profile:Professor Jeung Ku Kang email@example.com http://nanosf.kaist.ac.kr/ Nano Materials Simulation and Fabrication Laboratory Department of Materials Science and Engineering KAIST
Hydrogen-Natural Gas Hydrates Harvested by Natural Gas
A hydrogen-natural gas blend (HNGB) can be a game changer only if it can be stored safely and used as a sustainable clean energy resource. A recent study has suggested a new strategy for stably storing hydrogen, using natural gas as a stabilizer. The research proposed a practical gas phase modulator based synthesis of HNGB without generating chemical waste after dissociation for the immediate service. The research team of Professor Jae Woo Lee from the Department of Chemical and Biomolecular Engineering in collaboration with the Gwangju Institute of Science and Technology (GIST) demonstrated that the natural gas modulator based synthesis leads to significantly reduced synthesis pressure simultaneously with the formation of hydrogen clusters in the confined nanoporous cages of clathrate hydrates. This approach minimizes the environmental impact and reduces operation costs since clathrate hydrates do not generate any chemical waste in both the synthesis and decomposition processes. For the efficient storage and transportation of hydrogen, numerous materials have been investigated. Among others, clathrate hydrates offer distinct benefits. Clathrate hydrates are nanoporous inclusion compounds composed of a 3D network of polyhedral cages made of hydrogen-bonded ‘host’ water molecules and captured ‘guest’ gas or liquid molecules. In this study, the research team used two gases, methane and ethane, which have lower equilibrium conditions compared to hydrogen as thermodynamic stabilizers. As a result, they succeeded in stably storing the hydrogen-natural gas compound in hydrates. According to the composition ratio of methane and ethane, structure I or II hydrates can be formed, both of which can stably store hydrogen-natural gas in low-pressure conditions. The research team found that two hydrogen molecules are stored in small cages in tuned structure I hydrates, while up to three hydrogen molecules can be stored in both small and large cages in tuned structure II hydrates. Hydrates can store gas up to about 170-times its volume and the natural gas used as thermodynamic stabilizers in this study can also be used as an energy source. The research team developed technology to produce hydrates from ice, produced hydrogen-natural gas hydrates by substitution, and successfully observed that the tuning phenomenon only occurs when hydrogen is involved in hydrate formation from the start for both structures of hydrates. They expect that the findings can be applied to not only an energy-efficient gas storage material, but also a smart platform to utilize hydrogen natural gas blends, which can serve as a new alternative energy source with targeted hydrogen contents by designing synthetic pathways of mixed gas hydrates. The research was published online in Energy Storage Materials on June 6, with the title ‘One-step formation of hydrogen clusters in clathrate hydrates stabilized via natural gas blending’. Professor Lee said, “HNGB will utilize the existing natural gas infrastructure for transportation, so it is very likely that we can commercialize this hydrate system. We are investigating the kinetic performance through a follow-up strategy to increase the volume of gas storage. This study was funded by the National Research Foundation of Korea and BK21 plus program. (Figure1. Schematics showing the storage method for hydrogen in a natural gas hydrate using a substitution method and storage method directly from ice to a hydrogen-natural gas hydrate.) (Figure 2. Artificially synthesized and dissociated hydrogen-natural gas hydrates. The Raman spectra of tuned sI and sII hydrate showing the hydrogen clusters in each cage.)
Dr. Steven Chu Talks on Sustainable Energy Policy at KAIST
Nobel Laureate in physics and former US Energy Secretary Steven Chu called for concerted efforts to develop a more sustainable energy policy and portfolio at a lecture held at KAIST and a forum in Seoul on November 23. A policy with an energy mix including nuclear power and renewable energy could be ideal for retaining a stable energy supply given Korea’s very limited geographical conditions, Chu said during the Future Energy Forum in Seoul. He also held a lecture at KAIST’s Daejeon campus on “Climate Change, the Importance of Science and Policy in Achieving a Sustainable Future.” He said that unlike the United States, Korea and Japan have geographical limitations for generating enough renewable energy. "Wind speeds of more than 10 meters per second would allow wind power generation, but, South Korea's southernmost wind speed in Jeju is less than 8 meters per second, and the amount of sunshine is lower than in the Middle East. It is ideal to combine renewable energy with nuclear power plants," he said. Chu also stressed the role of science in achieving a sustainable future, citing many cases in foreign countries. For instance, Germany once decided to do away with nuclear power. However, their initial plan does not directly raise energy efficiency and the proportion of fossil fuels has led to an increase in the environmental issue of fine particular matter as well as carbon dioxide emission increases. He said that in the long term, renewable energy will emerge as major alternative resources, stressing the role of science in achieving a sustainable future. Without this alternative, we will eventually burn more fossil fuels and pollute the air. Chu also said that nuclear waste and safe plant operation will be a big concern, but it is technologically viable since Korea has already proven its prowess in nuclear power plant building and safety technology. Chu added, "Research in chemical energy storage through novel electrochemistry may lead to solutions, but for the next half century we will need additional energy-on-demand and carbon-free sources of energy from proven technologies." "While science, innovation and technology will no doubt lead to better solutions, sound government policies are needed to advance the transition to carbon-free energy needed to achieve a more sustainable world," he said. After serving as the US Secretary of Energy for four years from 2009 to 2013, Professor Chu returned to Stanford University, and currently holds a position of the William R. Kenan, Jr. Professor of Physics as well as Professor in the Department of Molecular and Cellular Physiology. Professor Chu is known for his research at Bell Labs and Stanford University regarding the cooling and trapping of atoms with laser light, for which he won the Nobel Prize in Physics in 1997.
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