DEPARTMENT of Electrochemistry of Biocatalytic and Metal-Air Systems

E-mail: kaisheva@bas.bg

Research and development in this department is performed in two main topics:

Gas-diffusion electrodes and metal-air cells and batteries

•   Air gas diffusion electrodes with new concept and materials
     –   highly hydrophobic porous electrochemically conductive carbon-based material
     –   highly effective porous non-platinum catalyst for oxygen reduction
•   Theoretical and experimental study of transport processes in porous media
•   Mathematical modeling and computer simulation of the processes in gas-diffusion electrodes
•   Development of mobile metal-air cells and batteries
     –   Primary zinc-air cells
     –   Mechanically rechargeable zinc-air cells
     –   Magnesium-air cells with non-aggressive electrolyte

Enzyme electrodes and electrochemical biosensors

•   Amperometic enzyme electrodes
     –   Membrane  enzyme electrodes
     –   Mediated enzyme electrodes
     –   New type enzyme-gas-diffusion electrodes in which oxygen needed for the enzymatic reaction is supplied in gas phase from the atmospheric air
•   Electrochemical biosensors
     –   For use in the medical practice
     –   For ecological control

SCIENTIFIC PROJECTS

Electrochemical biosensors for monitoring organic pollutants in the environment

Project Leader: Assoc. Prof. Anastassia Kaisheva

Financing: Bulgarian Academy of Sciences, National Fund of Scientific research

 The project is focused on research and development of electrochemical biosensors for monitoring of some organic pollutants in the environment, especially for detection of phenol, phenolic compounds and alcohols in waters and in the atmosphere.

As a result of wide investigations of enzyme electrodes using carbon materials and enzymes-oxidoreductases a new type of enzyme-gas-diffusion electrodes are developed. In this type of enzyme-gas-diffusion electrodes oxygen needed for the enzymatic reaction is supplied in gas phase from the atmospheric air trough a special porous hydrophobic gas-layer, similar to that in ordinary air-breathing gas-diffusion electrode.

The experiments have shown that the effective oxygen supply in the enzyme-gas-diffusion electrodes results in improved characteristics of the biosensors. Something more, the mode of oxygen supply in the enzyme-gas-diffusion electrodes allows biosensors using enzymes-oxidoreductases to be used in anaerobic media in which oxygen needed for the enzymatic reaction is absent.

A gas biosensor for monitoring of gaseous pollutant   in the atmosphere can also be constructed on the base of a enzyme-gas-diffusion electrodes. In such  gas bioesensor the gaseous analyte is supplied to the reaction zone through the porous hydrophobic gas-layer of the enzyme-gas-diffusion electrode together with the oxygen.

The research and development of electrochemical biosensors for monitoring organic pollutants in the environment include:

        - Development of biosensors for concentration of phenol and phenolic compounds in waters

        - Development of gas biosensors for detection and monitoring of phenols and alcohols in the air               

        - Mathematical modeling and computer simulation of the processes in enzyme-gas-diffusion electrodes

The realization of the project is expected to solve some basic problems of the electrochemical biosensors and  their application for detection and monitoring of hazardous organic compounds in the environment.

In the last years a new structural approach for the construction of the impedance model, based on a special technique, called Differential Impedance Analysis (DIA), has been developed. It increases the information capability and objectiveness of the impedance analysis because it extracts the impedance model from the experimental data. A sophisticated mathematical procedure AWACS and a catalogue with more than 20 basic impedance models, including their spectral presentation, support the new technique.  

mobile metal-air cells and batteries

Project Leader: Assoc. Prof. Anastassia Kaisheva

Financing: Bulgarian Academy of Sciences, ZOXY Energy Systems AG, Germany

The project is aimed to investigate various types of metal-air cells as mobile electrochemical power sources for use in navigation aids, signal devices, electronic communication systems, reserve power supply,  power supply for electrically driven cars, etc.

Typical for the metal-air power sources is that oxygen from the surrounding air is used as reactant which is electrochemically reduced on an invariant air gas-diffusion cathode with relatively small weight and volume. Various metals can be used as anodes in metal-air cells (Zn, Mg, Al, etc), the capacity of the cell being determined by the type of metal anode.

The major advantage of metal-air batteries over many other conventional batteries is their potentially high specific energy (Wh/kg), which is a result of the low equivalent weight of oxygen (8g/equivalent) compared to most oxidants that reacts as the cathode. This causes an enhanced interest in research and development of  metal-air systems.

Various types of metal-air cells and batteries have been developed in this department.