Scientists have successfully developed electret adsorbents and have started deve

As the second anniversary of his return to teach approaches, Professor Li Huiguang from the School of Science and Engineering at the Chinese University of Hong Kong, Shenzhen, has finally published his first-author Nature paper.

Before this, he studied and worked in Europe for nearly 10 years. After obtaining his doctoral degree from Ruhr University Bochum in Germany, he successively engaged in postdoctoral research at Ruhr University Bochum and Technical University of Munich in Germany.

He then joined the University of Cambridge in the UK to research carbon dioxide adsorbents. It was during his time in the UK that he completed the subject of this Nature paper.

The adsorption performance has been maintained at 100% for 11 consecutive days.

In the study, he and his collaborators used electrochemical technology to use the charged ions separated as adsorption sites, and developed a new type of adsorbent material, which was named the charged sorbent.The adsorption heat of the electret adsorbent reaches up to 137 kJ mol⁻¹, showing an extremely strong affinity for carbon dioxide, providing the necessary conditions for directly capturing ultra-low concentrations of carbon dioxide in the air.

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In continuous tests over 11 days, the adsorption performance of the electret adsorbent has always remained at 100%, and even after 14 months, the performance has only decreased by 8%.

In the direct air capture test, within less than 25 minutes, the electret adsorbent can reduce the concentration of carbon dioxide in the air to about 25 ppm.

At the same time, due to the good electrical conductivity of the electret adsorbent, it can quickly complete the desorption process of the adsorbent through the Joule heating method.

Based on this advantage, the electret adsorbent can directly use renewable energy for in-situ Joule heating desorption, which can greatly improve the energy utilization efficiency.Solid-state NMR testing data indicates that within an extremely short period of time, Joule heating can rapidly heat materials to 90°C, achieving complete desorption of carbon dioxide.

Compared to the carbonates in traditional methods, the desorption process of charged adsorbents completely bypasses the lattice energy barrier, thus allowing desorption to be completed at relatively low temperatures between 90°C and 100°C.

In addition, compared to traditional heating methods, by adopting Joule heating desorption technology, charged adsorbents can simultaneously have the advantages of high efficiency and low energy consumption.

The preparation of charged adsorbents adopts a principle similar to battery charging. In the low-cost pores of activated carbon, charged adsorbents can accumulate a large number of active hydroxyl ions, and quickly capture carbon dioxide in the air by forming carbonate (hydrogen) roots.

At the same time, charged adsorbents not only have a high chemical adsorption capacity, but also have low physical adsorption-desorption energy consumption, which can greatly reduce the energy cost of carbon capture.In addition, the raw materials for charged adsorbents are abundant and easily accessible, thus they can be directly used for carbon capture in the air.

With a highly customizable pore environment, it is expected that charged adsorbents will bring broad application prospects in the fields of chemical separation, catalysis, and so on.

Li Huaguang said: "In the near future, there is hope to create an air direct carbon capture system based on charged adsorbents."

At that time, when the air enters the interior of the system, it can make full contact with the charged adsorbent.

This allows carbon dioxide molecules to be adsorbed onto the surface of the charged adsorbent, and then undergo a chemical reaction at the adsorption active sites.At this time, the remaining gas molecules, such as nitrogen and oxygen, will return to the air through the outlet.

When the charged adsorbent reaches a state of saturation, the adsorption amount will reach its peak, and at this time, the charged adsorbent will stop working.

At this point, under the conditions of heating or low pressure, the adsorbed carbon dioxide can be desorbed, and the high-concentration carbon dioxide can be stored by pressurization. The charged adsorbent that has completed the desorption task can be reused.

In fact, before the publication of this paper, there have been many carbon capture technologies, so why is it still worth studying?

"Boldly" using the principle of supercapacitors to create new carbon capture technology.

In fact, before the publication of this paper, there have been many carbon capture technologies, so why is it still worth researching?In recent years, the issue of global climate change has become increasingly severe, with greenhouse gas emissions being considered one of the main causes. To achieve carbon neutrality and address climate change, countries are vigorously developing clean energy.

However, in the short term, fossil fuels are still difficult to completely replace. Therefore, how to effectively reduce carbon emissions has become a major challenge in the field of energy.

Under this background, carbon capture technology has received widespread attention and research. Carbon capture technology refers to the capture and separation of carbon dioxide from various emission sources, and its permanent storage or recycling.

However, the high cost of carbon capture technology has limited the large-scale application of this technology. How to reduce the energy consumption of carbon capture technology is the key to developing high-performance adsorption materials.

It is under this background that Li Huaiguang and his collaborators carried out this study. He said: "This work started with a bold idea, that is, to use the working principle of supercapacitors to separate ions to prepare adsorbents."At that time, Li Huaiguang and his colleagues researched various carbon capture technologies, and after clarifying the technical bottlenecks and key issues faced by these technologies, they established the route of electrified adsorbents.

Firstly, they tried a two-electrode system, using the structure of a button battery, to charge a supercapacitor composed of carbon film.

After a series of subsequent treatments, although electrified adsorbents could also be made, the test results showed that the carbon capture performance was not ideal.

Later, they changed the two-electrode system to a three-electrode system to precisely control the charging voltage.

During this period, Li Huaiguang and his collaborators successively screened and optimized various electrolytes, carbon materials, and other key components to study their impact on the efficiency of carbon dioxide capture.After numerous experiments and tests, the material and technical parameters were finally confirmed. Through this, they successfully created a new type of electret adsorbent, which demonstrated excellent performance in experimental tests.

Li Huaiguang recalled, "When we started this research, it was during the COVID-19 pandemic in Europe, and the experimental environment and time were quite limited."

At that time, to prevent infection among students and teachers, the Chemistry Department of the University of Cambridge designed a one-way traffic rule in addition to wearing masks.

When preparing electrode materials and conducting tests, Li Huaiguang needed to use two different laboratories.

"Due to the one-way rule, I had to go around the entire Chemistry Department building to get back to the starting point. The most interesting thing is that new students often got lost in the building," he said.And each laboratory has also set a maximum capacity for the number of people. Once the quota is full, one must wait for someone to come out before they can enter.

"This has greatly affected the progress of the experiment, but fortunately, the experiment has been going smoothly, and the collaborators from the United States and Italy have also provided a lot of help," said Li Huaiguang.

In the end, the relevant paper was published in Nature[1] with the title "Capturing carbon dioxide from air with charged-sorbents."

The reviewers commented:

Firstly, the idea of using a charging process similar to a battery to add hydroxide ions to the electrodes for the purpose of capturing carbon dioxide is very innovative.Secondly, the use of Joule heating and its impact on desorption kinetics is also very exciting.

In addition, Li Huaiguang and his colleagues have studied the adsorption and desorption mechanisms of adsorbent materials and carbon dioxide, which are considered new discoveries in the field by reviewers.

Currently, Professor Li Huaiguang's team, who has returned to the country to establish an independent group, is working with collaborators to transfer the laboratory technology of charged adsorbents to large-scale industrial production, and will continue to optimize energy consumption, cost, reliability, and other factors.

At the same time, he will also use computer simulation and machine learning methods to perform virtual screening and optimization for performance under various working conditions, with the aim of greatly improving experimental efficiency and success rate.

He also plans to further integrate AI technology into the carbon capture system, using AI algorithms to analyze the system's operational data in real time, and while automatically optimizing key process parameters, he hopes to improve the efficiency and stability of carbon capture as well.Through this, it is expected that during the pilot and demonstration phases, carbon capture systems will become smarter. "I believe that with continuous innovation and effort, this technology can become another powerful tool to combat climate change and achieve the 'dual carbon' goals," Li Huaiguang said in conclusion.