New evidence suggests we can generate electricity by collecting electrons naturally transported within plant cells. Could the energy of the next generation literally grow on trees?
Photosynthesis is arguably the most important solar energy storage process on Earth. This remarkable natural process is the source of both our food and most of our energy resources1—making plants the original solar panels. But while plants and some bacteria have been doing this for billions of years, it has only very recently occurred to humans that we could harness plants to produce electricity in this way.
Now, researchers reporting in ACS Applied Materials & Interfaces have used a succulent plant to create the first living bio-solar cell that runs on photosynthesis. Previously, harvesting an electrical current from a photosynthetic system has been achieved by immersion into an electrolyte solution; however, this study showed that the aqueous solution in the tissues of succulent plants can be used directly as a natural bio-photo electrochemical cell.2
This works because light falling on to the surface of the leaves drives a flow of electrons from water, ultimately generating 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—and without the addition of an exogenous electrolyte.2
An advantage of using succulents or cacti is that they have fleshy leaves with a significant water volume, protected by a rigid or waxy cuticle. In this experiment, that thick cuticle formed the infrastructure of the electrochemical cell. When connected into a circuit with an iron anode and platinum cathode and exposed to light, a single leaf produced up to 20 µA/cm2 of photocurrent density—and could continue producing current for over a day.2
While that might seem underwhelming, connecting multiple leaves in series could increase the voltage, and the model could also be used to catalyze hydrogen production. Other plants such as seaweed have also been found to generate a bias-free photocurrent even in the dark, which could offer huge utility for low-cost energy solar energy conversion technologies.3
Plants are critical for our planet and our survival in numerous ways. They provide food, oxygen, and many important materials and chemicals that we use in a multitude of products. Plants are also important as habitats for many other species, for land stabilization, and as carbon sinks. But perhaps now they will also prove to be a good source of electricity. Even more exciting, this model presents a method to simultaneously absorb CO2 while producing an electrical current with minimal engineering requirements. Could this finally be a big win for green energy?
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Recent Advances in the Processing and Manufacturing of Plant-Based Meat
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- Blankenship, R. E. Early Evolution of Photosynthesis. Plant Physiol. 2010, 154, 2, 434–348.
- Shlosberg, Y. et al. Self-Enclosed Bio-Photoelectrochemical Cell in Succulent Plants. ACS Appl. Mater. Interfaces 2022, 14, 48, 53761–53766.
- Shlosberg, Y. et al. Bioelectricity Generation from Live Marine Photosynthetic Macroalgae. Biosens. Bioelectron. 2022, 198, 113824.