Tuesday, May 24, 2022

Tiny skyscrapers help bacteria generate electricity from sunlight

Researchers from the University of Cambridge have developed 3D-printed tiny ‘skyscrapers’ for the communities of photosynthetic bacteria that turn sunlight, carbon dioxide, and water into energy. By creating grids of high-rise ‘nano-housing’ for these sun-loving bacteria, the team has broken new ground in the space.

The Cambridge researchers believe that providing these communities with the right kind of home increases the amount of energy they can extract by over an order of magnitude.

The photosynthetic bacteria or cyanobacteria are the most abundant life forms on Earth and need lots of sunlight to grow – like the lake surface in the summertime. In order to extract the energy they produce through photosynthesis, the bacteria need to be attached to electrodes.

“There’s been a bottleneck in terms of how much energy you can actually extract from photosynthetic systems, but no one understood where the bottleneck was,” said Dr. Jenny Zhang from the Yusuf Hamied Department of Chemistry, who led the research. “Most scientists assumed that the bottleneck was on the biological side, in the bacteria, but we’ve found that a substantial bottleneck is actually on the material side.”

Researchers 3D-printed custom electrodes out of metal oxide nanoparticles that are tailored to work with the cyanobacteria as they perform photosynthesis. These electrodes were printed as highly branched, densely packed pillar structures, like a tiny city. Researchers say the electrodes have excellent light-handling properties, like a high-rise apartment with lots of windows.

Cyanobacteria need something they can attach to and form a community with their neighbors. The electrodes allow for a balance between lots of surface area and lots of light – like a glass skyscraper. Once the self-assembling cyanobacteria were in their new home, the team found that they were more efficient than other current bioenergy technologies, such as biofuels.

The system increased the amount of energy extracted by over an order of magnitude over other methods for producing bioenergy from photosynthesis. The researchers were then able to extract the bacteria‘s waste electrons, leftover from photosynthesis, which could be used to power small electronics.

“I was surprised we were able to achieve the numbers we did – similar numbers have been predicted for many years, but this is the first time that these numbers have been shown experimentally,” said Zhang. “Cyanobacteria are versatile chemical factories. Our approach allows us to tap into their energy conversion pathway at an early point, which helps us understand how they carry out energy conversion so we can use their natural pathways for renewable fuel or chemical generation.”

The team’s printing technique also allows control over multiple length scales, making the structures highly customizable, which could benefit a wide range of fields.

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