Harvesting an electrical current from biological photosynthetic systems, such as live cells, is typically achieved by immersion of the system into an electrolyte solution. In new research, scientists at Technion in Israel show that the aqueous solution found in the tissues of succulent plants can be used directly as a natural bio-photo electrochemical cell.
Shlosberg et al. present a method to simultaneously absorb carbon dioxide while producing an electrical current with minimal engineering requirements. Image credit: Shlosberg et al., doi: 10.1021/acsami.2c15123.
In all living cells, from bacteria and fungi to plants and animals, electrons are shuttled around as part of natural, biochemical processes.
But if electrodes are present, the cells can actually generate electricity that can be used externally.
Researchers previously created fuel cells in this way with bacteria, but the microbes had to be constantly fed.
Instead, Technion’s Professor Noam Adir and his colleagues turned to photosynthesis to generate current.
During this process, light drives a flow of electrons from water that ultimately results in the generation of oxygen and sugar.
This means that living photosynthetic cells are constantly producing a flow of electrons that can be pulled away as a photocurrent and used to power an external circuit, just like a solar cell.
Certain plants — like the succulents found in arid environments — have thick cuticles to keep water and nutrients within their leaves.
The study authors wanted to test, for the first time, whether photosynthesis in succulents could create power for living solar cells using their internal water and nutrients as the electrolyte solution of an electrochemical cell.
They created a living solar cell using the ice plant (Corpuscularia lehmannii), a succulent plant species native to parts of the Eastern Cape Province of South Africa.
They inserted an iron anode and platinum cathode into one of the plant’s leaves and found that its voltage was 0.28 V.
When connected into a circuit, it produced up to 20 µA/cm2 of photocurrent density, when exposed to light and could continue producing current for over a day.
Though these numbers are less than that of a traditional alkaline battery, they are representative of just a single leaf.
Previous studies on similar organic devices suggest that connecting multiple leaves in series could increase the voltage.
The researchers specifically designed the living solar cell so that protons within the internal leaf solution could be combined to form hydrogen gas at the cathode, and this hydrogen could be collected and used in other applications.
“Our method could enable the development of future sustainable, multifunctional green energy technologies,” they said.
Their work appears in the journal ACS Applied Materials & Interfaces.
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Yaniv Shlosberg et al. 2022. Self-Enclosed Bio-Photoelectrochemical Cell in Succulent Plants. ACS Appl. Mater. Interfaces 14 (48): 53761-53766; doi: 10.1021/acsami.2c1512
