For many years, researchers have been striving to develop methods for obtaining electricity from bacteria. Researchers have now discovered how to make this process more efficient and sustainable.
The London Zoo has a camera that is solely powered by a plant photosynthesising that converts solar radiation to electricity. Bacteria in the soil collect and transfer electricity to the camera, enabling it to take a picture of the plant every 20 seconds.
For many years, scientists have been developing and improving methods to obtain electricity from bacteria, and today the research is so advanced that such devices using photosynthetic bacteria can generate enough electricity to power a microprocessor.
Now researchers have refined the method for obtaining energy from cyanobacteria so that the process is more environmentally sound by using electrically conducting polymers that can replace less sustainable rare-earth minerals.
“We are still at the early development stage for obtaining electricity from cyanobacteria, but there are interesting perspectives. Research is currently moving towards finding the most efficient method and achieving this in the most sustainable way,” explains a researcher behind the study, Pia Damlin, PhD Fellow, Materials Chemistry Research Group, Department of Chemistry, University of Turku, Finland.
The research has been published in Electrochimica Acta.
Creating organic semiconductors
Pia Damlin and colleagues have worked specifically on improving the electrode that captures the electricity through electrons from the bacteria.
Electrodes normally comprise materials made of indium tin oxide. Indium is a rare-earth metal that is mostly mined in countries that have problematic political systems or that pose human rights issues.
The researchers therefore investigated the potential of using electrically conducting polymers, especially poly(3,4-ethylenedioxythiophene) (PEDOT), which was fabricated using a new method developed in house. This material possesses several desirable properties for use as an electrode material for biophotovoltaics.
Another researcher involved in the study, Laura Wey, PhD, from Professor Yagut Allahverdiyeva-Rinne’s group at the University of Turku, Finland, says that any material suitable as an electrode to obtain energy from bacteria must be transparent so that light can pass through it and reach the bacteria. Other crucial criteria include sustainability, affordability, excellent conductivity and a large surface area that facilitates interaction with photosynthetic biocatalysts.
“Electrically conducting polymers are a class of organic polymers that can conduct electricity. These versatile materials find applications across diverse fields, including energy, sensors and biomedicine. PEDOT is one of the most commonly used electrically conducting polymers,” says Laura Wey.
Better than current electrodes
The researchers investigated PEDOT as a possible electrode in a device to extract electricity from bacteria.
Their studies, which took place with bacteria placed on the PEDOT electrode in liquid like the pond water where the bacterial naturally live, showed that the bacteria generated more electricity and transferred more current through the electrode under blue light than red light.
According to Pia Damlin and Laura Wey, this is interesting because cyanobacteria often yield more electricity under red than blue light.
The researchers also found that the thicker the PEDOT layer, the more current they could obtain.
Finally, the researchers also showed that they could obtain the same amount of electricity from the flat PEDOT electrode as with a flat electrode of indium tin oxide.
“On all parameters, we can make the process more efficient and sustainable with PEDOT than with the materials currently used today,” explains Pia Damlin.
Further optimisation
Pia Damlin and Laura Wey say that the research is still at a very early stage and that much more development is needed before biophotovoltaics becomes common.
For example, the researchers would like to investigate how the photocurrent yield can be further optimised by making the electrodes more porous to increase the surface area.
They will also investigate the potential of different strains of bacteria – including photosynthetic bacteria that tolerate high salt concentrations.
“Another objective is to create larger devices with increased capacity for directly generating electricity from bacteria. As we explore the potential, we can also assess how this sustainable electricity source aligns with current energy consumption patterns,” concludes Pia Damlin.
“Optoelectronic enhancement of photocurrent by cyanobacteria on sustainable AP-VPP-fabricated PEDOT electrodes” has been published in Electrochimica Acta. The research has been supported by the NordForsk Nordic Center of Excellence NordAqua, the Academy of Finland, Business Finland, the Fortum and Neste Foundation, the Jenny and Antti Wihuri Foundation and the Novo Nordisk Foundation.
