Chair of Applied Electrochemistry

Applied electrochemistry is an interdisciplinary field based on chemistry, physics, and materials science that focuses on the practical application of electrochemical phenomena and processes in technology and industry. It encompasses the development of electrode materials and electrolytes, the investigation and optimization of electrochemical reactions, and their use in energy conversion and storage systems, electrochemical analysis, corrosion protection, surface treatment of materials, and electrosynthesis. Applied electrochemistry bridges fundamental electrochemical knowledge with engineering solutions and real-world applications.

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Main research directions

Synthesis, modification, and characterization of electrode materials for supercapacitors, batteries, and other energy storage systems

PhD Maarja Paalo, PhD Thomas Thomberg, PhD Alar Jänes

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The synthesis of carbon materials using various methods and from different precursors for diverse applications (supercapacitors, batteries, gas storage/separation) has been carried out at the Chair of Applied Electrochemistry for over 30 years. To produce carbon materials with different porosities (micro- and mesoporosity, specific surface area, etc.) and structures (amorphous, graphitic, etc.), a wide range of approaches has been employed and studied, including halogenation of carbides, hydrothermal carbonization of various carbohydrates (glucose, sucrose, etc.), high-temperature pyrolysis, and the activation of both carbon-rich raw materials (well-decomposed Estonian peat, wood processing residues, lignin, straw, used tires, etc.) and carbon materials using different reagents (KOH, NaOH, ZnCl₂, H₂O, CO₂ etc.), in order to make them suitable for the aforementioned applications.

Research on the synthesis and investigation of battery cathode materials has been conducted at the Chair of Applied Electrochemistry since 2018 (Alar Jänes, Ronald Väli), with a focus on the development of various transition metal oxides, polyanionic compounds, and Prussian blue analogues for lithium- and sodium-ion batteries. Using different synthesis methods (solid-state synthesis, sol–gel, hydrothermal synthesis, etc.), the structure–property relationships of cathode materials have been investigated, as well as strategies for improving their electrochemical performance.

Key publications (last 10 years):

Development of batteries

PhD Alar Jänes, PhD Meelis Härmas, PhD Maarja Paalo

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In the field of applied electrochemistry, extensive fundamental and applied research is conducted for the development of Li-, Na-, K-, and Zn-ion batteries, with the aim of creating more efficient, safer, and sustainable energy storage solutions. The research focuses on the development of new electrode materials and electrolytes, as well as a thorough understanding of their structural and electrochemical properties. Modern electrochemical characterization techniques are employed in the studies, including cyclic voltammetry, galvanostatic charge–discharge, electrochemical impedance spectroscopy, and in situ and operando methods, which allow monitoring of processes occurring in batteries during operation. Particular emphasis is placed on sodium- and zinc-ion batteries as cost-effective and environmentally friendly alternatives to lithium-ion batteries. The mechanisms of ion deposition and dissolution, the cyclic stability of materials, and their long-term reliability are investigated. Research in this field combines fundamental electrochemistry, materials science, and engineering, contributing both to international cutting-edge science and the development of practical and sustainable energy storage technologies.

Key publications:

Development of high power and energy density supercapacitors

PhD Alar Jänes, PhD Thomas Thomberg, PhD Maarja Paalo, PhD Meelis Härmas

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Research on carbon materials in both aqueous and non-aqueous media began at the Institute of Chemistry, University of Tartu, in 1991. The study of supercapacitors gained particular momentum in 1997, when Tartu Technologies Ltd invited electrochemists from the University of Tartu to develop non-aqueous supercapacitors. Electrochemists Alar Jänes, Gunnar Nurk, Priit Möller, and others worked intensively at Tartu Technologies Ltd until 2005, although occasional collaborations continued thereafter. Since then, investigations have explored the use of porous carbons derived from binary and ternary carbides, as well as from aged glucose solutions, sugar, and well-decomposed Estonian peat, for high-energy and high-power density supercapacitors. It has been demonstrated that high power densities can be achieved in various acetonitrile- and ternary organic carbonate-based electrolytes and their mixtures (propylene carbonate, ethyl methyl carbonate, ethylene carbonate, etc.). Supercapacitors based on ionic liquids were first studied in 2008, revealing that while the use of ionic liquids as electrolytes increases energy density, it somewhat reduces power density. The highest power densities are primarily achievable in supercapacitors with mesoporous carbon electrodes, which have been electrochemically treated under faradaic reaction conditions to dissolve active surface sites from the carbon surface.

Development of hybrid capacitors

PhD Alar Jänes, PhD Jaanus Eskusson

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Hybrid capacitors are systems for electrical energy storage in which one electrode undergoes traditional physical adsorption of ions, while the other electrode participates in an ultrafast faradaic charge-transfer process. There is no strict boundary between electric double-layer capacitors, hybrid capacitors, and batteries, because under overvoltage conditions in capacitors and during hybrid capacitor operation, faradaic processes occur in addition to the charging of the electric double layer. Since the capacitances associated with some faradaic processes are several times higher than those in electric double-layer capacitor charging, efforts are made to combine 2-electrode systems, where, for example, cation reduction occurs at the negative electrode. A significant increase in capacitance is also observed in processes involving partial charge transfer associated with anion adsorption, particularly at charge densities where halide or other anions are strongly, specifically adsorbed, partially releasing their negative charge. In such capacitors, energy density can increase up to 2.5 times at low power densities. However, the power densities of these systems decrease at moderate energy densities compared to conventional electric double-layer capacitors.

Synthesis and investigation of virus‑inactivating nanostructured materials for use in air filters, face masks, and surface‑protective coatings

PhD Thomas Thomberg

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This topic is novel at the University of Tartu, and the development of such materials began in 2020. As a result of this work, nanostructured films of Cu and its oxides, Ag nanoclusters and their oxides, and Zn and its compounds are obtained, deposited onto face masks via vacuum evaporation. Depending on the preparation method, these films exhibit highly variable antiviral activity against influenza viruses or SARS-CoV-2.

Highly active materials are produced using the electrospinning method, in which solutions of Cu, Ag, and Zn compounds (salts, oxides, etc.) dissolved or dispersed in an organic solvent are simultaneously combined with a polymer solution under a high-voltage direct current. These compounds deposit onto the surface of polymer nanolayers or into the interior of porous polymer nanofibers. Such fibrous materials are capable of capturing much smaller virus-containing aerosol particles from the air than commercial face masks or filters. Since some of the Cu, Ag, and Zn nanoclusters, or their compound nanoclusters, are entrapped within the nanostructured yet porous polymer fibers, the resulting material is highly stable in air and can be used for extended periods to purify air in critical environments. Vacuum-electromagnetically deposited nanostructured Cu and Cu(I) oxides, as well as Ag-activated face masks, can be safely used for significantly longer durations than conventional masks, greatly reducing environmental pollution caused by disposable masks. Applying a similar approach to air filter materials can substantially decrease the need for single-use masks.

Key publications:

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