When it comes to making great fuel cells, it’s all about the catalyst. A good catalyst will result in faster, better chemical reactions and, thus, increased energy output. Fuel cells today typically rely on platinum-based catalists. But scientists at American University believe that spinach – considered a “superfood” because it is full of nutrients – can produce a highly renewable carbon-rich catalyst, based on their experimental evidence described. in a recent paper published in the journal ACS Omega. Popeye will definitely approve.
The notion of exploitation of the photosynthetic properties of spinach has been around for almost 40 years now. Spinach is abundant, inexpensive, easy to grow, and rich in iron and nitrogen. Many (many!) Years ago, as a developing young science writer, I attended a talk at the conference of physicist Elias Greenbaum (then with Oak Ridge National Labs) about his research related to spinach. Specifically, he is interested in protein-based “reaction centers” in spinach leaves which are the main mechanism for photosynthesis – the chemical process by which plants make 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. Much scientific interest is in the PS1, which acts like a small photosensitive battery, absorbing energy from sunlight and emitting electrons with almost 100-percent efficiency. In essence, energy from sunlight converts water into an oxygen molecule, a positively charged hydrogen ion, and a free electron. These three molecules then combine to form a sugar molecule. PS1s are capable of generating light-induced electric flow in fractions of a second.
True, this is not a huge amount of energy, but a day is enough to run small molecular machines. Greenbaum’s work is committed to the development of artificial retinas, for example, replacing damaged retinal cells of light-sensitive PS1s to restore sight to those suffering from a poor eye condition. Because PS1s can be tweaked to act like diodes, passing in one direction but not in the other, they can be used to generate gateways for a rudimentary computer processor if they can connect them by molecular-sized wires made of carbon nanotubes.
Greenbaum is just one of many researchers interested in the electrochemical properties of spinach. For example, in 2012, scientists at Vanderbilt University combined PS1s with silicon to obtain current levels nearly 1,000 times higher than achieved when protein centers were deposited on metals, with a modest increase of voltage. The goal is to eventually develop “biohybrid” solar cells that can compete with standard silicon solar cells in terms of voltage and current levels. A 2014 paper by Chinese researchers reported on experiments to collect active carbon from spinach for capacitor electrodes, while just last December, another group of Chinese scientists examined the potential production of spinach-based nanocomposites to serve as photocatalysts.