People usually think of plants as a source of food, oxygen and decoration, but not as a source of electricity. However, scientists have discovered that by harnessing the natural transport of electrons within plant cells, it is possible to generate electricity as part of a green biological solar cell. In a recent study published in the journal ACS Applied Materials and Interfaces, researchers have used a succulent plant for the first time to create a living “biosolar cell” that runs on photosynthesis.
From bacteria and fungi to plants and animals, electrons are naturally transported in all living cells as part of biological processes. By introducing electrodes, these cells can be used to generate electricity that can be used externally. Previous research has used bacteria to create fuel cells, but it requires constant feeding. This new approach uses photosynthesis, the process by which plants convert light energy into chemical energy, to generate electrical currents.
In this process, light drives a flow of electrons from water that eventually leads to the production of oxygen and sugar. This means that living photosynthetic cells are constantly producing a stream of electrons that can be pulled as “photocurrent” and used to power external circuits, much like a solar cell.
The succulent plant shown here could become a living solar cell, using photosynthesis to power a circuit. Credit: Adapted from ACS Applied Materials and Interfaces, 2022, DOI: 10.1021/acsami.2c15123
Yaniv Shlosberg, Gadi Schuster and Adir wanted to see if photosynthesis in succulents could use their internal water and nutrients as an electrochemical cell electrolyte solution to create energy for a living solar cell.
The researchers used the succulent plant Corpuscularia lehmannii, also known as the “short-leaved ice plant,” to create a living solar cell. They inserted an iron anode and platinum cathode into one of the plant’s leaves and found a voltage of 0.28 V. When connected to a circuit, it produced a photocurrent density of up to 20 μA/cm2 and, when exposed to light, could continue to produce current for more than a day. While these numbers are smaller than conventional alkaline batteries, they do, after all, represent only a single leaf.
Previous research on similar organic devices has shown that connecting multiple leaves in series can increase the voltage. The team specifically designed the living solar cells so that protons within the internal leaf solution could combine at the cathode to form hydrogen gas, which could be collected and used for other applications. The researchers say their approach could lead to the development of sustainable, multifunctional green energy technologies in the future.