Artificial photosynthesis may soon be a reality – splitting water into hydrogen and oxygen. You only have to look as far as your garden to observe one of the most common chemical reactions in nature at work pulling apart water molecules (H2O) and splitting them into carbohydrates and oxygen (O2). Nature provides the template for this process using the energy from sunlight to fuel the reaction. Here's a video showing the basic process:
In your garden, your plants use the natural pigment chlorophyll to absorb sunlight, while catalysts produce the water-splitting reaction through cellular respiration. This process was used as a biological template by a team of MIT researchers, led by Dr. Angela Belcher, Germeshausen Professor of Materials Science and Engineering and Biological Engineering, to emulate the “highly organized photosynthetic system” evolved in blue-green algae (cyanobacteria) and other plants to separate oxygen from hydrogen.
Taking their clues from nature, they engineered a novel alternative to this process, as described in a recently published research paper in Nature Nanotechnology. The team decided to alter the common, harmless M13 bacterial virus so that it would attract and bind with molecules of a iridium oxide catalyst and the biological pigment zinc porphyrins. The viruses were used as wire-like devices to split the oxygen from water molecules. Thomas Mallouk, the DuPont Professor of Materials Chemistry and Physics at Pennsylvania State University, is quoted as saying that he finds the research “…an extremely clever piece of work that addresses one of the most difficult problems in artificial photosynthesis, namely, the nanoscale organization of the components in order to control electron transfer rates.”
Rather than splitting hydrogen from water, Dr. Belcher’s team focused on splitting oxygen from water (oxidation), which is more challenging from a technical perspective. Splitting hydrogen from water, however, ultimately may prove to be more interesting. Hydrogen is an important alternative to some of the problems of the current hydrocarbon-based economy. Free hydrogen is relatively rare on Earth, and thus it is typically generated by electrolysis of water, an expensive process that requires electrical energy. Using sunlight rather than electricity to make hydrogen from water could greatly improve the efficiency of the process. Hydrogen can then be stored and used to generate electricity using a fuel cell, or burned as fuel for cars and trucks. Dr. Belcher’s team is already working on a biological template to efficiently split hydrogen from water similar to the one they successfully used to split oxygen from water. The hydrogen atoms in their current process get split into component protons and electrons. The new process under development would combine these back into hydrogen atoms and molecules.
Splitting hydrogen from water could help make hydrogen a more viable alternative to coal, nuclear, and fossil fuels.
Dr. Belcher’s interest in alternative energy and sustainable technologies is not new. The winner of a 2004 MacArthur Foundation genius grant for using genetically engineered viruses as templates for nanoscale electronic components, she says she was inspired by the ability of abalone mollusks to extract dissolved chemicals from water to manufacture their incredible pearly shells. “Suddenly, I wondered, what if we could assemble materials like the abalone does — but not be limited to one element? What if we could bond protein to other elements in the periodic table and grow new materials?” In 2006, her insight led to the use of the M13 virus to assemble batteries. The genetically altered viruses, which are harmless to humans, pull ions from a solution to form both the positive- and negative-charged ends of a lithium-ion battery. “We’re letting biology help us work on solving those problems, solving what the next-next generation batteries are going to be,” says Dr. Belcher. She talks about her earlier work with the M13 virus in this video:
During a recent visit to the MIT campus, President Obama met with Dr. Belcher and other energy researchers. He stressed the need for new, efficient and clean energy technologies — something very much underscored by the recent Gulf of Mexico oil spill. Taking clues from photosynthesis to develop a biological template that uses viruses and sunlight to split hydrogen from water could help make hydrogen a more viable alternative to coal, nuclear, and fossil fuels.
NOTE: Jimmy Stewart’s character in You Can’t Take it With You talks about artificial photosynthesis: http://www.youtube.com/watch?v=KWKHmE8_Mkc
