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Popeye will approve: Spinach may hold key to renewable fuel cell catalysts

Popeye reaches for a can of spinach in a still from an unidentified <em>Popeye</em> film, c.  1945. Scientists at the American University believe that leafy greens have the potential to help power future fuel cells.  “/><figcaption class=
Zoom in / Popeye reaches for a box of spinach in a piggy bank of unidentified Popeye film, c. 1945. Scientists at the American University believe that green leaves have the potential to help power future fuel cells.

Paramount Pictures / Courtesy of Getty Image

As for the production of efficient fuel cells, it’s all about the catalyst. A good catalyst will lead to faster, more efficient chemical reactions and thus increase energy power. Today’s fuel cells typically rely on platinum-based catalysts. But researchers at the American University believe that spinach – considered a “superfood” because it is full of nutrients – would create an excellent renewable carbon-rich catalyst, based on their evidence-based experiments described in a recent article published in the journal ACS Omega. . Popeye would definitely approve.

The idea of ​​using the photosynthetic properties of spinach has existed for about 40 years. Spinach is plentiful, inexpensive, easy to grow and rich in iron and nitrogen. Many (many!) Years ago, as a young science writer, I attended a physics conference by Elias Greenbaum (then with Oak Ridge National Labs) about his spinach research. In particular, he is interested in the protein “reaction centers” in spinach leaves, which are the main mechanism of photosynthesis – the chemical process by which plants convert carbon dioxide into oxygen and carbohydrates.

There are two types of reaction centers. One type, known as Photosystem 1 (PS1), converts carbon dioxide into sugar; the other, Photosystem 2 (PS2), separates water to produce oxygen. Most of the scientific interest is in the PS1, which acts as a small photosensitive battery that absorbs energy from sunlight and emits electrons with almost 100 percent efficiency. In essence, the energy from sunlight converts water into a molecule of oxygen, a positively charged hydrogen ion and a free electron. These three molecules then combine to form a sugar molecule. PS1s can generate a light-induced flow of electricity in fractions of a second.

Of course, this is not a huge amount of energy, but it is enough for one day to operate small molecular machines. Greenbaum’s work promises to build artificial retinas, for example, replacing damaged retinal cells with light-sensitive PS1 to restore vision in people with degenerative eye conditions. Because PS1s can be modified to behave like diodes by passing current in one direction but not the other, they can be used to build logic ports for a simple computer processor if one can connect them via wires of size of a molecule made of carbon nanotubes.

Greenbaum is just one of many researchers interested in the electrochemical properties of spinach. For example, in 2012, researchers at Vanderbilt University combined PS1 with silicon to obtain current levels nearly 1,000 times higher than those achieved by depositing protein centers on metals, along with a moderate increase in voltage. The goal was ultimately to build “biohybrid” solar cells that could compete with standard silicon solar cells in terms of voltage and current levels. A 2014 report by Chinese researchers reported experiments to collect activated carbon from spinach for capacitor electrodes, while just last December, another group of Chinese scientists explored the potential for creating spinach-based nanocomposites to serve as photocatalysts.

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