Physicists from St Petersburg University develop a new method of bonding carbon nanotubes to a substrate for supercapacitors

Single-walled carbon nanotubes are cylindrical structures with diameters of one to several tens of nanometers, formed by a single layer of carbon atoms. They have high electrical conductivity, mechanical strength and chemical stability.

The results of the research supported by a grant from the Russian Science Foundation are published in the scientific journal Nanomaterials.

Multi-walled nanotubes most often consist of multiple nested single-walled nanotubes, which are used in a variety of fields. For example, they are used in mechanical engineering to increase the strength and wear resistance of car body parts and tires, and in microelectronics to create a new generation of super-efficient devices. 

The scientists from St Petersburg University have long been studying the use of nanotubes as a basis for developing novel electrode materials for supercapacitors. For example, the University’s experts believe that the use of multi-walled nanotubes is a more promising option than single-walled nanotubes due to the variety of their shapes and configurations. Additionally, the process of separating MWCNTs from their bundles with subsequent dispersion has been well studied and is therefore less labor-intensive. 

Particular attention is currently being paid to the development of high-efficiency supercapacitors, i.e. supercapacitors with increased power, long life and high charge-discharge rates, based on novel composite electrode materials.

The research was carried out within the framework of the project supported by a grant from the Russian Science Foundation titled "New nanocomposites based on electrically conductive poly-[M(Salen)] (M = Co, Ni, Cu) polymers and carbon nanostructures for supercapacitors: atomic-electronic structure and electrochemical properties according to XPS, NEXAFS, EXAFS spectra and electrochemical measurements".

The use of nanocomposites based on multi-walled carbon nanotubes and electrically conductive polymers as the material for such electrodes makes it possible to increase the capacitive properties of the supercapacitor. This is possible due to the large surface area, which increases the capacitance of the electrical double layer, and the additional contribution of pseudocapacitance from the polymer. 

One of the challenges in the practical application of such materials is the poor adhesion of the nanotubes to the current-collecting substrate. Currently, this is solved by adding polymer binders when preparing the electrode. Such binders can be polyvinylidene fluoride (PVDF), carboxymethylcellulose (CMC), styrene-butadiene latex (SBL) and other materials. However, as the scientists from St Petersburg University note, binders reduce electrical conductivity and also affect the porous structure of the resulting material.

My colleagues and I have proposed a new approach to increase the adhesion of multi-walled nanotubes to the surface of a metal (titanium) substrate. The method we have developed involves modification of the interface at the nanotube-substrate interface using a continuous beam of helium ions.

Petr Korusenko, a co-author of the research, Senior Research Associate in the Department of Solid State Electronics at St Petersburg University

To estimate the effectiveness of the proposed method, the physicists from St Petersburg University conducted a series of studies to determine the optimal time for irradiating the nanotubes. It turned out that the best result was achieved after 20 minutes of irradiation: in this case, adhesion improved by 57% compared to the untreated system. According to the University’s scientists, this bonding is the result of the formation of chemical C—O—Ti bonds between titanium and carbon atoms with the participation of oxygen-containing functional groups, which are localized on defects in the nanotube walls formed during ion irradiation. 

The approach proposed by the researchers makes it possible to dispense with polymer binders, while maintaining the developed surface of the initial material on the surface of the titanium substrate. This technology can be applied not only for the production of supercapacitors, but also for lithium-ion batteries.

St Petersburg University, the oldest university in Russia, was founded on 28 January (8 February) 1724. This is the day when Peter the Great issued a decree establishing the University and the Russian Academy of Sciences. Today, St Petersburg University is an internationally recognised centre for education, research and culture. In 2024, St Petersburg University celebrates its 300th anniversary. 

The plan of events during the celebration of the anniversary of the University was approved at the meeting of the Organising Committee for the celebration of St Petersburg University’s 300th anniversary. The meeting was chaired by Dmitry Chernyshenko, Deputy Prime Minister of the Russian Federation. Among the events are: the naming of a minor planet in honour of St Petersburg University; the issuance of bank cards with a special design; and the branding of the aircraft of the Rossiya Airlines to name just a few. To mark the 300th anniversary of St Petersburg University, a postage stamp depicting the Twelve Collegia building and the monument to Count Sergey Uvarov was issued. 

By the decision of the Governor of St Petersburg Alexander Beglov, 2024 is a year of the 300th anniversary of St Petersburg University in St Petersburg. On the day of the University’s 300th anniversary torches will be lit on the Rostral Columns on the Spit of Vasilyevsky Island. St Petersburg University flags will be raised on the Palace Bridge. The city public transport will be decorated with the University’s symbols. New tourist maps will feature the locations of the University buildings, with thematic and historical materials about the University placed nearby. During St Petersburg’s City Day celebrations in May 2024, St Petersburg University will be a participating venue. The traditional "Scarlet Sails Festival" will also be dedicated to the anniversaries of St Petersburg University and the Russian Academy of Sciences. Additionally, the University has launched a website dedicated to the upcoming holiday. The website contains information about outstanding University staff, students, and alumni; scientific achievements; and details of preparations for the anniversary.