Generally, energy storage systems with a discharge time of more than 4 hours are referred to as long-term energy storage in the industry. Such systems can adjust and balance the fluctuations in new energy generation, storing energy to avoid grid congestion when energy is surplus, and exporting power during peak consumption. Flow battery is a promising "dark horse" in the field of long-term energy storage.
In 1974, scientists L. H. That the biggest difference from traditional batteries is that the positive and negative electrolytes of liquid flow batteries are stored in external reservoirs. These active substances are transported to the stack by the circulating pump, and the redox reaction occurs on the surface of the electrode to realize the storage and release of energy. Because the energy is stored in the electrolyte, this means that the energy storage of this battery no longer depends on the size of the electrode, but on the total amount of electrolyte-expansion, only need to expand the size of the tank. Among them, the water-based organic flow battery uses water as the medium, which is an efficient energy storage means with high safety and environmental friendliness.
While improving the utilization rate of clean energy, human beings still need to fight against the "side effects" of traditional fossil energy consumption: the greenhouse effect brings sustained and severe challenges to human survival and development. The efficient capture of carbon dioxide has become a key issue to reduce the impact of greenhouse gases on the climate and create a carbon neutral closed-loop. At present, amine washing, strong alkaline solution absorption, direct air capture of solid amines and amino acids are common technologies, but these methods have some imperfections, including toxicity, corrosiveness, difficult material degradation, high energy consumption and so on.
Since its establishment, Wang Pan Laboratory, School of Science, West Lake University, has made a series of research achievements in the field of water flow battery energy storage (J. Am. Chem. Soc. 2023, 145, 5778-5785; Joule, 2021, 5, 2437-2449; In previous studies Angew. Chem. Int., they found that phenazine organic molecules would cause "pH swing" in aqueous solution due to their unique proton-coupled redox characteristics during charging and discharging. So he thought about how to use this phenomenon and use the flow battery system to act as the "carbon catcher".
So, what kind of structure of molecules can accomplish this mission? In other words, finding small molecules that are "useful, applicable, and easy to use" is what they are good at.
In 2021, Wang Pan's laboratory and the cooperative team developed a new bionic design of water-soluble phenazine compound 1,6-AFP, which endowed the aqueous organic flow battery system with excellent stability; this is also the first achievement of this laboratory in West Lake. Later, they developed a series of new members of the phenazine "family" based on different functions and application scenarios. The new member 1,8-ESP shares the same "skeleton" (mother nucleus) as the previously reported 1,6-AFP, but is grafted with different "limbs" (functional groups). Functional groups are atoms or groups of atoms that affect the physical and chemical properties of organic compounds. The previous generation of small molecules used amino acids, but this generation, the team replaced them with sulfonic groups.
As a result, the "old skeleton" has sprouted new vitality: it can not only realize the energy storage function of water flow batteries, but also capture and release carbon dioxide.
 occurs in the system: when charging, 1,8-ESP (active molecule) gains electrons, is reduced and takes a proton from water, making the solution alkaline, and hydroxide (OH-) reacts with carbon dioxide to produce carbonate (CO32-) and bicarbonate (HCO3-). The discharge process is the opposite. In fact, it only takes a basic chemical concept to understand that alkaline liquids can absorb carbon dioxide. When the battery is charged, the neutral solution containing 1,8-ESP undergoes a pH change to become alkaline, thereby absorbing the charged carbon dioxide simultaneously; when the battery is discharged, the liquid changes from alkaline to neutral, thereby naturally releasing the previously captured carbon dioxide. </p><p style=)
Further, the researchers tested the performance of the 1,8-ESP aqueous flow battery and found that it had a series of superior performances. Not to mention the complicated data report card, generally speaking, this small molecule and its developed batteries have high water solubility, good carbon dioxide capture performance, high stability, good oxidation resistance and low energy cost, which are suitable for "from acid to alkali".
In other words, Wang Pan's laboratory has successfully achieved efficient and high-capacity capture of carbon dioxide. In practical operation, the battery system with 1,8-ESP as the active material can be used not only as a carbon dioxide capture system, but also as an energy storage system. The system can adjust and respond to energy storage and carbon capture in time according to the market and actual demand, so as to obtain the maximum economic benefit. As mentioned
earlier, designing and synthesizing new organic materials and compounds and finding different application scenarios for them are the main axes of Wang Pan's laboratory. As early as around the Spring Festival of 2021, after the previous achievement on high-temperature water organic flow battery was published in Joule magazine, they started the synthesis of 1,8-ESP.
Obviously, they are not satisfied with just using it to build a single energy storage system, staying in their own research "comfort zone", but want to make it better "shine and heat". Pang Shuai, one of the co-authors of the article and a doctoral student of Wang Pan's laboratory, recalled that for this reason, they had Michael J.
with Harvard University, the "originator" of the field of organic flow batteries in the water system, and in the past two years, this young laboratory, which had only been established for more than three years, had shown the greatest characteristics of the West Lakers: daring to think and do. Experience in the design and synthesis of materials and the exploration of the mechanism of chemical reaction process are their advantages. Building a carbon dioxide absorption environment from scratch is a field they have never been involved in before, but they are not afraid to start from scratch. The laboratory resolutely seeks cross-border cooperation and works with the top laboratories at home and abroad.
The results are not easy to come by, but for the researchers who always aim at "better", every breakthrough means a new beginning. After 1,8-ESP, Wang Pan's laboratory has been on the way to find small molecules with stronger antioxidant capacity. They want to find a more ideal organic material, hoping that it can be used as a basis for efficient carbon dioxide capture directly from the air. "Normal air contains only about 400-500 ppm of carbon dioxide, but 21% of oxygen, so its antioxidant capacity is very important," Wang Pan explained.
So what happens after capturing more carbon dioxide? And where will it be released? That is to say, the energy provided by clean energy, on the one hand, can be stored electrochemically, on the other hand, can be used to capture carbon dioxide from the air (sources include factory exhaust, automobile exhaust, etc., as long as human beings are still using fossil fuels, the carbon dioxide produced can not be avoided); Then, the carbon dioxide is used as raw material for further conversion to produce chemicals with higher added value and clean energy (such as methanol and ethylene), thus achieving a virtuous circle..
Wang Pan Laboratory
works in the interdisciplinary fields of organic synthetic chemistry, energy chemistry and material chemistry, devotes itself to the design and development of new organic functional materials, and explores the mutual transformation of organic small molecules and polymer materials between light energy, electric energy and chemical energy. Its application in the frontier interdisciplinary fields of energy conversion and storage is studied. Develop functional membrane materials and new energy storage materials, and study their applications in electrochemical reactions and energy storage. Recently, the
team has achieved some excellent results in the field of water flow battery energy storage. By means of organic synthetic chemistry and material function-oriented molecular design and precise synthesis, a series of phenazine water-soluble organic energy storage materials have been developed for electrochemical energy storage. This kind of flow battery system has the characteristics of long life, low capacity fading, safety and environmental protection, and has strong application value in water electrochemical flow energy storage system, which provides a basis for solving the current energy and environmental problems. The work was published in Joule, J. Am. Chem. Soc., Angew. Chem. Int., a leading journal in chemistry and energy.
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