Harvesting an electrical current from biological photosynthesis systems is usually achieved by immersing the system in an electrolyte solution. Now, for the first time, researchers at the Technion-Israel Institute of Technology have used a succulent plant to create a living “bio-solar cell” that runs on photosynthesis.

All natural, biological processes of living cells – from bacteria and fungi to plants and animals – involve the movement of electrons. However, the cells can produce external electricity if electrodes are present. Researchers used bacteria to make fuel cells in the past, but the microbes constantly needed nourishment. Instead, scientists, including Noam Adir’s team, have turned to photosynthesis to generate power.

Light drives a stream of water electrons during this process, which eventually produce oxygen and sugar. Like a solar cell, this means that living photosynthetic cells have a continuous flow of electrons that can be drawn away as a “photocurrent” and used to power an external circuit.

Some plants have thick cuticles to retain water and nutrients in their leaves, such as the succulents found in arid regions. As the electrolyte solution of an electrochemical cell, Yaniv Shlosberg, Gadi Schuster and Adir planned to investigate for the first time whether photosynthesis in succulents could produce energy for living solar cells.

Using the succulent Corpuscularia lehmannii, also known as the ‘ice plant’, the researchers produced a living solar cell. They tested one of the plant’s leaves by inserting an iron anode and a platinum cathode into it, and they found it had a voltage of 0.28 V. It can produce power for more than a day when on a circuit connected and achieve photocurrent densities of up to 20 A/cm2.

Although these figures are lower than those of a regular alkaline battery, they only apply to one blade. According to previous studies on analog organic devices, numerous leaves connected in series can increase voltage. The team deliberately created the living solar cell so that protons in the internal leaf solution can combine at the cathode to make hydrogen gas, which can then be collected and used for other purposes. According to the researchers, their approach could help to develop multifunctional, sustainable green energy solutions in the future.

Magazine reference:

  1. Yaniv Shlosberg, Gadi Schuster and Noam Adir. Self-enclosed bio-photoelectrochemical cell in succulent plants. ACS applied materials and interfaces. DOI: 10.1021/acsami.2c15123