"Tiny skyscraper" electrodes boost bioenergy output of blue-green algae
Scientists have long studied the abilities of photosynthetic bacteria that turn sunlight, carbon dioxide and water into energy, and by giving these communities a home likened to a high-rise apartment block, a team has broken new ground in this space. These tiny grids of "nano-housing" create the optimal environment to not just foster the rapid growth of these bacteria, but take their energy-harvesting potential to new heights.
Also known as cyanobacteria or perhaps more familiarly, blue-green algae, photosynthetic bacteria can be found in all types of water, where they use sunlight to make their own food. Their natural proficiency at this task has inspired many promising avenues of research into renewable energy, from bionic mushrooms that generate electricity, to algae-fueled bioreactors that soak up carbon dioxide, to self-contained solutions that offer a blueprint for commercial artificial photosynthesis systems.
Cyanobacteria thrive in environments like lake surfaces as they require lots of sunlight to grow, and a team at the University of Cambridge has made a breakthrough that came about by experimenting with ways to better satisfy these needs. Another thing for the team to consider was that to gather any of the energy they produce through photosynthesis, the bacteria need to be attached to electrodes. By crafting electrodes that also promote the growth of the bacteria, the scientists are effectively trying to kill two birds with one stone.
“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, 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.”
The team used 3D printing to produce electrodes made out of metal oxide nanoparticles, which were arranged in densely packed sets of pillars, like a tiny city. This city played host to the cyanobacteria, which went on to generate electricity with great efficiency. So much so, the system increased the amount of energy that can be extracted from cyanobacteria by "over an order of magnitude."
“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.”
Another strength of the approach is that the printing technique can be adapted to produce structures of different heights and scales, meaning the tiny cities can be tailored to potentially suit a range of applications. The study therefore not just shows how energy from this form of photosynthesis might be better captured, but opens up new possibilities around electrode design.
“The electrodes have excellent light-handling properties, like a high-rise apartment with lots of windows,” said Zhang. “Cyanobacteria need something they can attach to and form a community with their neighbors. Our electrodes allow for a balance between lots of surface area and lots of light – like a glass skyscraper.”
The research was published in the journal Nature Materials.
Source: University of Cambridge