Professor In Seop Chang's research team has solved the electric power overshoot problem for microbial fuel cells

□ Professor In Seop Chang of the Gwangju Institute of Science and Technology (GIST) School of Earth Sciences and Environmental engineering has solved the "power-overshoot" phenomenon for microbial fuel cells. The research is expected to increase the practical applications of microbial fuel cells that use microorganisms to create electricity.

 

  * Microbial Fuel Cell: Microbial fuel cell technology is capable of recovering electrons from organic materials and microorganisms and converting them into electrical energy.

  * Power overshoot: A phenomenon in which the current produced in the low voltage range decreases and becomes lower than the current produced in the relatively high voltage range. This occurs in a discharging test that is generally performed to evaluate the performance of microbial fuel cells.

 

Unlike chemical fuel cells, microbial fuel cells that are based on microorganisms must be capable of producing stable currents under various conditions of voltage demand in order for the system to have practical uses. However, the power overshoot phenomenon has been regarded as one of the difficulties in the practical application of microbial fuel cells because it makes it difficult to produce a stable low voltage current.

 

  ∘ Depletion of organic substances acting as fuel, increase in internal resistance of the system, and formation of a biofilm on the cathode are possible causes for the electric power overshoot phenomenon.

 

A power overshoot phenomenon that occurs during discharge experiments to evaluate the performance of microbial fuel cells requires an auxiliary current system to overcome this phenomenon.

 

□ The researchers realized that the causes of power overshoot are the factors affecting the production capacity of the electrons. When the amount of electrons generated in the negative electrode is less than the reducing power in the positive electrode, 'power overshoot' phenomenon occurs, which can be eliminated by supplying sufficient electrons externally.

 

  ∘ The team found that the current value that should be increased with decreasing voltage was reduced in the discharge experiment conducted to measure the performance of a pair of microbial fuel cells among the multiple electrode MFCs. The electrons were supplied from the cathode portion existing in the same system.

  * Multiple Electrode Fuel Cell (Multiple Electrode MFC): A system in which multiple MFCs coexist in a single reactor. All negative electrodes share the same electrolyte, and the positive electrode is exposed to the air and separated.

 

  ∘ As a result, the power overshoot phenomenon did not occur in the discharging experiment process of the system which received the deficient electron, and the stable high current could be produced even when the voltage was lowered.

 

 

□ Professor In Seop Chang said, "This study provides a way to solve the power overshoot problem by using a simple method, so we have laid the foundation of microbial fuel cell technology that can produce stable current under various required voltage."

 

  ∘ This research was led by Professor In Seop Chang (correspondent author) and carried out by Ph.D. candidate Bong-kyu Kim (first author) and was supported by the National Research Foundation. It was published on January 11, 2017, in ChemSusChem.