Osaka City University Develops CO2 Consuming Biofuel Cell Utilizing Microalgae Spirulina

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Osaka City University announced on April 25, 2018, that it succeeded in developing a new biofuel cell system with the functions of a solar cell and the ability of carbon dioxide conversion. Utilizing the photosynthesis function of spirulina, a biomass of dark-green unicellular microalgae, this solar-light driven biofuel cell generates electricity by consuming CO2 in water as source material and produces formic acid as a byproduct while generating electricity.

The team led by Prof. Yutaka Amao in the Research Center for Artificial Photosynthesis of Osaka City University had focused on the effective oxygen-evolution photosynthetic function activity spirulina shows in water. Using a device containing CO2-saturated buffer solution with two electrodes coupled with each other therein, an electrode on which a photosynthetic membrane derived from spirulina is immobilized and another electrode on which formic-acid dehydrogenase is immobilized, they found a certain amount of electric current (measuring 55 microamperes) flowing through the circuit when visible-light is applied to the photosynthetic-membrane immobilized electrode. They also found that formic acid was produced above the formic-acid-dehydrogenase immobilized electrode by reduction of CO2. They also confirmed the evolution of oxygen and reduction of hydrogen carbonate ions derived from CO2.

Thus, this biofuel cell introduced a new technology to create bioenergy that not only consumes CO2, a major global warming substance, as a useful source for generating power, but also produces an organic molecule, formic acid. Formic acid has a large usage potential, such as a hydrogen-energy storage medium, a synthetic material for organic chemicals, and a solvent for inorganic-organic chemical compounds. It is expected that this technology will become an effective tool to realize a low-carbon society.