NSU Student Received Diploma for Best Presentation at International Symposium on Carbon Utilization in Catalysis in China

The 11th International Symposium on Carbon Use in Catalysis CarboCat-11 was held in Beijing (China) from May 28 to 31. The event was dedicated to advanced carbon materials in catalysis, the use of artificial intelligence in the process of producing “green” fuel, and decarbonization technologies. The only representative from Russia was a 5th-year student of the Faculty of Natural Sciences (FENS) specialized in “Fundamental and Applied Chemistry” at Novosibirsk State University, an employee of the G. K. Boreskov Institute of Catalysis SB RAS.Olga Borodina. She presented the results of the study conducted by her under the scientific supervision of a research associate of the Laboratory of Composite Materials for Electronics at FEN NSU, (senior researcher of the Engineering Center IK SO RAN), Candidate of Chemical SciencesPetra Yeletskogo. This work is carried out as part of the completion of the diploma thesis — “Synthesis and study of activated carbons with a highly developed porous structure from compacted vegetable raw materials.”

The CarboCat International Symposium is held once every two years and is the largest scientific event in the world dedicated to the use of carbon in catalysis. This year, within the framework of seven sections, 67 oral presentations were heard, including plenary lectures from leading experts in this research field, presentations by experienced researchers, as well as oral and poster presentations by scientists, which were evaluated by authoritative representatives of the scientific community. Olga Borodina spoke in the section “Advanced Synthetic Methods for Carbon-based Catalysts” with the report “FINE-TUNING POROSITY THROUGH H3PO4 ACTIVATION OF PINE NUT SHELL: ACTIVATED CARBONS FOR IONIC LIQUID BASED SUPERCAPACITORSHer speech caused great interest among the audience, and as a result, the symposium recognized it as one of the best oral presentations.

Superconductors— these are devices for storing energy that occupy an intermediate position between regular capacitors and electrochemical batteries. These devices are capable of charging and discharging very quickly with high power density. They have a number of advantages — long service life (10-15 years), stable operation under extreme (low and high) temperature conditions, and safety due to the absence of risk of fire or explosion in case of short circuit. They do not require complex power controllers for charging. To increase the electrochemical capacity, porous electrode materials are introduced into supercapacitors.The most accessible and widely used type of electrode is activated carbon. Supercapacitors are used as power sources in electric and hybrid vehicles, as well as in electronics. There are two types — based on aqueous and non-aqueous electrolytes. This study is related to non-aqueous electrolytes, which include organic electrolytes and ionic liquids, since they are expected to operate over a wider potential window, which potentially allows accumulating more energy, and also — at necessity — at low temperatures.

It is important that currently there is no production of superconductors using non-aqueous electrolytes in Russia. However, in the event of a successful development of this method, the possibility of organizing industrial production of this material may arise.

The promising raw material for obtaining activated carbon is plant biomass. Within the framework of the work, natural raw materials were used — cedar nut shells, since their harvesting is carried out on the territory of the Russian Federation on an industrial scale. It is also possible to use as raw materials fruit stones and shells of other nuts. Their high density and hardness can be partially inherited by the resulting carbon materials.

—There are carbon materials of various types, and they are used accordingly for different types of tasks. The common activated carbon, which is sold in pharmacies, is used as an adsorbent. Usually, such activated carbons are obtained by the method of steam-gas activation. Activated carbons, used by us in supercapacitors on non-aqueous electrolytes, are obtained by the method of phosphoric acid activation., — Olga Borodina explained.

The project involves two teams of researchers: one is engaged in obtaining activated carbons, the other — testing the obtained samples. The first team conducts the main part of the research at the Composite Materials Laboratory for Electronics of NGU, the second — at the G.K. Boreskov Institute of Catalysis based on the Engineering Center.

For the production of a supercapacitor, electrode materials with maximum specific surface area are necessary. Specific surface area is the total surface area of substances relative to their mass. It is measured in m²/g. At the same time, the area of the entire internal surface of the porous structure is taken into account. The smaller the particle size and the higher the porosity of the material, the greater its specific surface area.

Materials for electrodes of supercapacitors with non-aqueous electrolytes should have characteristics such as specific surface area (more than 1500 m2/g) and a micro-mesoporous structure with a high share of surface area accessible to the electrolyte. Activation with phosphoric acid allows obtaining the desired textural characteristics and a higher yield compared to activation methods using other substances.

—We applied the method of phosphoric acid activation and obtained carbons with a specific surface area of up to 2700 m2/g. This is a very high indicator and an excellent result. It means that the material we obtained has a very high porosity. We also demonstrated that our methodology is reproducible for other types of natural raw materials (except cedar nuts) — we tested the shells of various nuts, as well as fruit stones and certain types of loose herbaceous raw materials. During these experiments, it was established that it is precisely from raw materials of increased density that it is possible to obtain carbons with a sufficiently high specific surface area.Therefore, our method can be applied not only in Siberia, using cedar nut shell as raw material, but also in regions with a milder and warmer climate, where another raw material is available, for example, apricot and peach pits or coconut shell., — Olga Borodina said.

Using the phosphorus-acid activation method, scientists mixed crushed cedar nut shell with concentrated phosphorus acid, then placed it in a drying cabinet and heated it at 200 degrees for 24 hours. Then they carried out the activation of the resulting pre-product in a vertical quartz reactor in an argon atmosphere at 500 degrees. Activated carbon with high porosity was obtained at the output.

Then, in a series of experiments, researchers found that the obtained material was not sufficiently stable after conducting a large number of charging-discharging cycles of the supercapacitor — after performing another stage of heat treatment at an elevated temperature and in a microwave reactor, the desired stability of the obtained activated carbons was achieved. At this stage, the method was optimized and scaled up. In the future, it is possible to obtain activated carbons with high porosity in larger volumes.

—Patents for obtaining activated carbons from cedar nut shells and creating a supercapacitor based on nanostructured carbon material were filed in 2024. Since then, we have done a large amount of work to improve and stabilize the method of synthesizing activated carbon by 10 and 100 times. Initially, at the laboratory level per experiment, about 4 grams of carbon were obtained, and after scaling up by a hundred times — respectively, about half a kilogram.At the same time, most of the material was reproduced — after scaling, it was possible to obtain activated carbons with a surface area of more than 2 thousand square meters per gram, which is enough to draw a conclusion about the reproducibility of the method and on a larger scale, — Olga Borodina said.

Work was also carried out on the possibility of reusing phosphoric acid as an activating agent. A young researcher explained that there are several types of carbon activation, but activation with phosphoric acid is distinguished by the fact that after obtaining the activated carbon and washing it in the filtrate, a mixture of polyphosphoric acid remains, which is a diluted solution of phosphoric acid. If it is subjected to heating and subsequent concentration, the same activating agent can be obtained and used again.This is very important for the prospect of scaling up the production of activated carbon.

Another advantage of this type of activation over others is that when it is used, the activated carbon content at the specified surface area value is 30-40%, whereas with alkaline activation it is only 5-10%. All these results were presented in detail by the young researcher in her speech at the symposium.

—Previously, I had not participated in an international conference of such a high level. Moreover, this was my first presentation in English. Therefore, I was very surprised when I found out that my report was recognized as the best. Within the framework of this conference, there were many very interesting works, including those on amorphous carbons and various carbon materials doped with heteroatoms. These topics fall within my field of scientific interests, and it is precisely this development that I intend to pursue during my graduate studies while writing my dissertation.We plan to dope activated carbons (introduce nitrogen atoms) and use these materials as carriers for palladium catalysts. Therefore, the presence of many reports devoted to this topic in the program pleased me very much — it testifies to the demand for this research direction in the global science community. For me, this was undoubtedly very interesting and useful., — Olga Borodina said.