NTU researchers use bacteria to generate energy and hydrogen fuel

NTU researchers created a hybrid fuel cell from E.coli

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E. coli acts as the “driver,” or catalyst, to the Microbial Fuel Cell. anyaivanova/Shutterstock http://bit.ly/1miZv38

NTU researchers have found an eco-friendly way to produce hydrogen gas, which can be used as fuel.

First, a chemical is added to a culture of E.coli bacteria to produce electricity. Such bacteria are commonly found in the environment, in the intestines of people and animals and some strains that can cause diarrhoea and food poisoning.

Under sunlight, the electricity helps to break up water into its components of hydrogen and oxygen.

“Not only are we able to use bacteria to clean water and to break down waste, we can also use the electrons that are produced by the bacteria to feed into a system that can help us to produce 70 times more hydrogen gas,” said Associate Professor Joachim Loo from NTU’s Singapore Centre for Environmental Life Sciences Engineering.

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The research was headed by A/Prof. Joachim Loo (School of Materials Science & Engineering, NTU & SCELSE), and involved the efforts of engineers, chemists and microbiologists. Credit: SCELSE

“Currently there are actual products out there that use bacteria to produce electricity, but these are all stand-alone systems.

“At the same time, we are also working in the area of solar fuels, where we actually use sunlight to split water into hydrogen and oxygen, but these have always been stand-alone systems. So for the first time, we are showing that a hybrid system of combining both together, we get a more efficient production of hydrogen gas.”

Professor Loo also said using hydrogen gas can help reduce reliance on fossil fuels. The team hopes to develop the idea into a commercial product in the coming years.

How does it actually work?

E.coli acts as a catalyst in this new hybrid fuel cell that splits hydrogen from water with remarkable efficiency. Its curious workings are detailed in a study published in the journal NPJ Biofilms and Microbiomes.

Photoelectrochemical (PEC) cells harness solar energy to send an electrical current through a sample of water splitting them to produce several hydrogen molecules and groups of oxygen-hydrogen ions. If this hydrogen can be stored, it can be ignited and burned at a future date in order to produce energy. Thus, PEC cells represent the key component of hydrogen fuel cells.

A microbial fuel cell (MFC) is somewhat similar, but instead of using solar power, the electrical current is generated using the electricity produced by a bacteria. The MFC is divided between an oxygen-depleted (anoxic) and oxygen-rich (oxic) region. A fuel – in this instance a chemical substrate that the bacteria would naturally use in order to produce energy – is mixed with a specific bacteria in the anoxic section.

As the bacteria uses it up, carbon dioxide is emitted, along with free electrons and protons. The protons pass through a membrane to one side of the cell, and the electrons are attracted towards the oppositely charged electrode on the other side of the cell. This difference in charge sets up a voltage, which produces a current within an electrical circuit. When the electrodes encounter the protons in the oxic side of the cell, water is produced.

The NTU researchers used  a PEC cell and a MFC in conjunction with each other. First off, slightly modified versions of their own PEC cells and MFCs were created. A custom gold-titanium oxide electrode system was used for the PEC cell, increasing its ability to conduct electricity. E. coli was chosen to be the MFC’s bacteria, and their membranes were injected with conjugated oligoelectrolytes (COEs), a class of compounds that improve the ability of the bacteria to transfer electrical charge.

The MFC is allowed to operate as it normally does, but this charge is transferred to the PEC cell, where it supplements the current already being produced by incoming solar energy. All things considered, the enhanced current generated by this PEC-MFC hybrid is reported to be 70 times greater than that of a PEC operating on its own.

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(a) Schematic representation of charge separation and movement in Au-TiO2 hollow sphere photo-anode. (b) Mechanistic diagram of the PEC-MFC hybrid system. Green dots represent electrons liberated during photoelectrochemical water splitting at the Au-TiO2 hollow sphere photo-anode. Blue dots represent electrons liberated by E. coli during metabolism of the organic source and interaction with COEs.

Source: Channel NewsAsia, IFLS, SCELSE

The original paper can be accessed here.

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