By: Dr. Christine Jurasinski; LabLearner Staff Scientist
“Why do we need to understand photosynthesis?” This may be a question that students all over the world, including LabLearner students ask. For many, the information about a plant process may seem unrelated to their current or future interests. But, what research has shown us over and over again is that one never knows how fields, concepts, and technology will interact. Some of the latest research from MIT proves just that.
Dr. Angela Belcher and colleagues have found a way to use a photosynthetic-like process to split water in order to create hydrogen fuel. For years, researchers have been contemplating how to create this type of artificial photosynthesis. Dr. Belcher and her team now appear to have taken the first step in not only creating artificial photosynthesis but also in using it as a way to produce alternative fuels.
From an energy level, LabLearner students should recall that photosynthesis involves the conversion of light to chemical energy. Light from the sun is used to drive a chemical reaction which produces oxygen and sugars from carbon dioxide and water. Many will recognize the chemical equation for this overall process
Although the equation above makes it appear as if all of this occurs in one step, in reality, photosynthesis involves many steps and reactions. Essential to the process are plant pigments including the pigment chlorophyll. Plant pigments absorb or capture photons and thus the energy of light. Ultimately, in most plants, the energy is transferred to molecules of chlorophyll. Once absorbed, this energy then causes the transfer of electrons from chlorophyll molecules to other molecules within a plant’s cell. These molecules in turn transport electrons to other molecules. This process is called electron transfer and produces energy. This energy is used to drive the reactions that produce sugar from carbon dioxide. In addition, as a part of this electron transfer, water molecules are split producing hydrogen and oxygen.
Dr. Belcher and her colleagues have mimicked these processes on a nano-scale. To do this they used a harmless virus called M13, a pigment called zinc porphyrin, and a catalyst called iridium oxide. They altered the virus so that it would attract and bind to the molecules of pigment and catalyst. The final structure resembled a thin wire with a coating around it. The virus was the wire and the pigments and catalysts the coating. When exposed to sunlight, the pigments absorbed photons of light and transferred energy down the length of the virus/wire much like the chlorphyll and other pigments in plants. This energy was then used by the catalyst to split water that surrounded the virus/wire into oxygen and protons and electrons; a process similar to that which occurs during electron transfer in plant cells.
(image: A computer visualization of the biologically-based system shows the virus itself (in yellow) with molecules of pigment (in pink) and of the metal catalyst (brown spheres) attached to its surface. The pigment and catalyst cause water molecules to split apart when they come in contact. Click on image to view original article. Graphic courtesy of Angela Belcher.)
Once the protons and electrons produced from the splitting of water re-combine, hydrogen can be produced. It is this last half of the process on which Dr. Belcher and colleagues are currently working. They anticipate completing this last step as well as making a more affordable prototype for artificial photosynthesis within the next two years.
So why is all of this important and how does it relate to what LabLearner students learn? Well, currently water can be split, and hydrogen made using electricity. However, the generation of electricity often comes from fossil fuels. Other researchers have used solar panels to produce electricity, which is then used to split water, but this system is less efficient because of its multiple steps. The system created by Dr. Belcher would skip many of the intermediate steps and create hydrogen directly from sunlight, just like photosynthesis. If this type of system can be created on a larger scale, solar energy could be used to split water into oxygen and hydrogen. The hydrogen could be stored in fuel cells and then used later to produce electricity or converted into other liquid fuels. The result would be a more efficient and “green” method of producing alternative fuels.
As for relating to the LabLearner curriculum, artificial photosynthesis requires knowledge of the photosynthetic process, properties of light, energy transfer, chemical reactions, and electron flow. These topics are those studied by both elementary and middle school students in CELLs such as Chemistry, Matter and Interactions, Forms of Energy, Light, Exploring Electricity, Chemical Reactions, Electricity and Magnetism, Photosynthesis, and Light and Optics.
Finally, consider whether this and future research would evolve if Dr. Belcher and others had never learned about photosynthesis. Her research as well as that of researchers in all other fields is showing us that the future lies in the combination rather than the isolation of knowledge. You just never know when you will use what you’ve learned and how it will affect the future.
