From TMU to the World. Professor Seiji Yamazoe, his “technology for rapid capture of CO₂ from ambient air” R&D, and what he values in research

Tokyo Metropolitan University is strengthening its research capabilities and accelerating globalization in line with the vision statement, “Pioneering the global future from Tokyo through the power of scholarship.” TMU undertakes research across diverse areas from basic to applied research, and research on metropolitan issues taking advantage of our location in Tokyo, with the intention of contributing to the development of Tokyo, and in turn, the future of the world.

It is within that research effort that Professor Seiji Yamazoe, in the Graduate School of Science and Faculty of Science, discovered “technology for rapid capture of CO2 from ambient air,” which has attracted a lot of attention from across the world. Below is our interview with him.
We asked him about what sparked his research, some of the finer details, and what he values in his research lab.

Technology for rapid capture of CO2 from ambient air, attracting worldwide attention

Professor Seiji Yamazoe (Faculty of Science)
⸺ What is your current specialization?

My specialization is catalytic chemistry. A catalyst is a substance that accelerates a specific chemical reaction. In catalytic chemistry, we research the structures and properties of these catalysts, the mechanisms of catalytic reactions, catalyst design, and so on. Within that research, I am investigating catalytic applications that take advantage of the unique structures and functions of “functional materials,” which demonstrate specific functions and respond to external stimuli, materials like those used in angular velocity sensors and touch panels.

I have been straddling several research areas, so there are other research areas I have experience in. In my student days at Kyoto University, I developed photocatalytic reaction systems for the purification of exhaust gases. During my time as an Assistant Professor in the Graduate School of Science and Technology at Ryukoku University, my focus was on functional materials, researching the development of the synthesis and functions of materials used in electronic devices, such as solar cells, piezoelectric materials, and transparent conductive films. As Assistant Professor in the Graduate School of Science at the University of Tokyo, I was involved in research into metal clusters where the numbers of atoms comprising substances are controlled by atomic unit1, as well as research into elucidating the physical properties and precision synthesis of metal oxide clusters.

I have spread my research effort broadly and shallowly, rather than digging deep into one thing, but what I have been consistent about is taking on the challenges of new things and research that nobody else is doing.

1: Substances where several to several tens of molecules or atoms of the same type are coupled by interaction

⸺ At TMU you are developing functional materials and researching catalytic applications, and you presented your research into technology for rapid capture of CO2 from ambient air in May 2022. Could you tell us about that technology?

It’s a technology that absorbs low-concentration CO2 in ambient air in an amine solution, ultimately to release and capture CO2 at high concentrations. Employing the phenomenon called phase separation2, where the substances in a solution separate into their liquid and solid phases, we have at least doubled the speed of the conventional method of CO2 capture, and we have discovered that by dispersing into the solution the solid called carbamic acid, a product of the chemical reaction between the amine solution and the CO2, it is possible to easily release the captured CO2 by heating it to about 60°C.

A feature of this technology is its improvement of the CO2 absorption efficiency over conventional technologies. Those conventional technologies have not been capable of efficiently absorbing the extremely low concentration of CO2 in ambient air, which is about 400 ppm (0.04%). Even in air with high concentrations of CO2, like exhaust gases, its efficiency is between 70 and 90%. But now with the technology we have developed, we can absorb CO2 from ambient air with at least 95% efficiency.

2: The generation of two distinguishable phases from a single homogeneous mixture

⸺ Could you tell us about some of the highlights of this discovery?

I think one highlight is that it uses phase separation in a series of capture technologies. It is actually not unusual to have a reaction where amine solution absorbs CO2 and solid carbamic acid precipitates out. This is a known phenomenon in organic chemistry, and if anything, it has been considered “difficult to extract CO2 from solid carbamic acid.”

However, this reaction between amine solution and CO2 was new to me when we first started this research, so I did not have the pre-existing attitude that “it is difficult to extract CO2 from solid carbamic acid.” The fact that we embarked on this research project from a new perspective, a phase separation perspective, and that we were not tied down by the pre-existing attitude that “it is difficult to extract CO2 from solid carbamic acid” were connected to our discovery.

Another highlight of this research is that we found a way to easily release CO2. For example, the conventional method for trial operation aimed at practical applications involves technology that causes CO2 to react with calcium ions or potassium ions to capture the CO2 as calcium carbonate or potassium carbonate. Yet, with this method, you need enormous amounts of energy to release the CO2, so unless it is heated to at least 800°C, it just won’t release the CO2.

With the method we discovered, you can separate out the CO2 at about 60°C, so it is very simple, and it does not use a lot of energy. Carbamic acid is stable as a solid and is very well suited to storage and transportation, so after absorbing the CO2, it can be moved to a different location where the CO2 can be taken out again. We have succeeded in creating technology that has a variety of possible applications.

⸺ When this technology is put to practical application, what contributions to society will it enable?

I believe its biggest contribution will be in achieving a carbon neutral world.

They say that if we continue as we are going and don’t take any countermeasures, the temperature of this planet we live on will increase by at least 1.5 degrees by 2050 and there will be even more abnormal weather, and so on. To prevent a future like that, we will need to capture all the CO2 emissions from the energy we use in our daily lives and in industry. Carbon neutrality aims to bring net CO2 emissions to zero by capturing those CO2 emissions at a separate location.

Although everywhere in the world has committed to achieving net zero CO2 emissions, with current technology, it is difficult to capture the CO2 spread so thinly in the atmosphere. Our discovery offers better CO2 absorption efficiency and we believe that if it is employed in CO2 capture equipment, it will enable cost reductions and downsizing of conventional equipment. If we can capture CO2 in a range of different places in our living environments, we should be able to accelerate the pace of progress toward a carbon neutral world.

I would like students to bring unfettered thinking to experimentation, free from preconceptions

⸺ How do you feel about this research receiving so much global attention?

The reaction has been bigger than we imagined. I was quite surprised. The fact is, our discovery is the product of chance. Originally we were looking into converting the CO2 in ambient air into useful compounds using catalysts, but a student noticed that a solid was produced through that process, even without a catalyst. Although it is not a new reaction, we thought it was good because of its simplicity, so we tied it into the development of the present technology.

Although I am proud that our research produced top-class data that holds its own, even against the most advanced technology in the world, I feel extremely grateful because I never imagined it would receive this much attention worldwide. I would be glad if this technology proved to be a spark that accelerates solutions to environmental problems.

⸺ What are the things you most value in your lab?

I regularly put across to my students the importance of not looking too deeply into previous research but bringing themselves to their experimentation without preconceptions. This research into technology for rapid capture of CO2 from ambient air is a case in point. It was precisely because I did not have a deep knowledge of the amine solution reaction that I was able to bring to this research ideas like phase separation and low-temperature CO2 release from solid carbamic acid, an approach that we have not seen in researchers till now.

Of course, studying is important. But, there is also the argument that it gets difficult to launch yourself into new challenges if your head is too full of knowledge. There are a lot of things that you will see for the first time through experimentation, and sometimes a trivial idea that at first glance looks worthless can be the key to a breakthrough, so I don’t want you to be too bound up in what you have learned, I want you to engage in experimentation with unfettered thinking. I think that in pursuing research, being a little short of knowledge is just about right.

⸺ How should the researchers of the future face their research? Do you think they should bring an awareness of social problems?

No, personally I don’t believe they need necessarily bring an awareness of social problems to their research. That’s because learning is the pursuit of truth, separate from social problems. For example, there are a lot of researchers in the Faculty of Science who are unquestionably progressing their research on the basis of the pursuit of truth, and who work out phenomena that have occurred. They believe that they can move the research another step forward by figuring out how observed phenomena work and theorizing, which ultimately leads to improvements for society.

Meanwhile, they research and develop new technologies to solve problems in society and meet the needs of the world in engineering faculties. I think if you do your research in anticipation of the outcome, you need to have a strong focus on problems in society.

The approach you should take differs according to the way you want to go about your research.

I want to educate students who can bring free thinking to their research and succeed on the global stage

⸺ Are there any overseas students in your lab?

We have two overseas students, one from China and the other from Thailand. The Thai student is interested in Japanese and is capable of everyday conversation and simple scientific discussion in Japanese. But basically we communicate in English when it comes to more elaborate discussions about our research, studying the data, and so on.

⸺ How do you want to educate your students?

Well, I want to educate students so that they have broad-ranging knowledge and experience, and can succeed on the global stage. From my experience, the world of research also needs researchers who are generalists and have a high level of knowledge across multiple areas, rather than delving deeper into one specialization. That’s why in my lab we carry out the whole series of research steps, making a material, performing a reaction, then analyzing the material and the reaction. Some labs specialize in analysis, others in reactions, but one of the distinctive features of my lab is that students get to experience everything in a well-balanced way. I would be glad to have students who want to engage in research with a sense of enjoyment and free thought come to my lab.

⸺ Last, what would you say to overseas students who want to study at TMU?

I have been to various universities, but TMU welcomes and supports overseas students, so it’s a good university for students from other countries. Actually, for every 5.7 postgraduate students there is one from overseas. The Faculty of Science and Graduate School of Science at TMU offer lectures in English too, so I really hope you do come to study here, without any worries about language.

Most students can keep a good balance moving between study and research, so they get good exposure to stimulation through their interactions and discussions.

TMU boasts one of the best research capabilities in Japan. I think the campus is sufficiently well equipped to satisfy students who want to devote themselves to research. I hope you consider studying at TMU. And I look forward to meeting you.