When it comes to producing efficient fuel cells, it’s all about the catalyst. A good catalyst will result in faster, more efficient chemical reactions and thus increased energy production. Today’s fuel cells are typically dependent on platinum-based catalysts. But researchers at American University believe that spinach – considered a “superfood” because it is so rich in nutrients, would make an excellent renewable carbon-rich catalyst based on their proof-of-principle experiments described in a recent article published in the journal. ACS Omega. Popeye would certainly approve of that.
The notion of utilizing the photosynthetic properties of spinach has been around for about 40 years now. Spinach is plentiful, inexpensive, easy to grow and rich in iron and nitrogen. Many (many!) Years ago, as a budding young science writer, I attended a conference talk by physicist Elias Greenbaum (then with Oak Ridge National Labs) on his spinach-related research. Specifically, he was interested in the protein-based “reaction centers” of spinach leaves, which are the basic 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 second photo system 2 (PS2) shares water to produce oxygen. Most of the scientific interest is the PS1, which acts as a small light-sensitive battery that absorbs energy from sunlight and emits electrons with almost 100 percent efficiency. Essentially, energy from sunlight converts water into an oxygen molecule, a positively charged hydrogen ion, and a free electron. These three molecules are then combined to form a sugar molecule. PS1s are capable of generating a light-induced stream of electricity in fractions of a second.
Granted, it’s not a huge amount of power, but it’s enough for one day to run small molecular machines. Greenbaum’s work promised to build artificial retinas, for example, to replace damaged retinal cells with photosensitive PS1s to restore vision in those suffering from a degenerative eye condition. Since PS1s can be adapted to behave like diodes that pass current in one direction but not the other, they could be used to construct logic gates for a rudimentary computer processor, if one could connect them via molecular-sized wires made of carbon nanotubes.
Greenbaum is just one of many researchers interested in the electrochemical properties of spinach. For example, researchers at Vanderbilt University in 2012 combined PS1s with silicon to obtain current levels almost 1,000 times higher than those obtained by depositing the protein centers on metals along with a modest increase in voltage. The goal was eventually to build “biohybrid” solar cells that could compete with standard silicon solar cells in terms of voltage and current levels. A 2014 paper by Chinese researchers reported on experiments collecting activated carbon from spinach into capacitor electrodes, while another group of Chinese researchers last December explored the potential of making spinach-based nanocomposites to act as photocatalysts.