We often want to imitate nature for near perfect results. But sometimes it just remains a desire. In its quest for green and clean energy mankind is searching for that magical method that can split water into hydrogen and oxygen. Nature performs this task wonderfully through the process of photosynthesis. Man is still facing challenges in duplicating that process in the laboratory. If we are able to split water into oxygen and hydrogen in the presence of sunlight we will be able to harness the potential of hydrogen as a clean and green fuel. Till date man-made systems are quite inefficient, time consuming, money consuming and often require additional use of chemical agents.
Researchers at the Weizmann Institute Organic Chemistry Department under the leadership of Prof. David Milstein have developed a novel way of splitting water molecules that can separate oxygen from water and bind the atoms in a different molecule. This technique leaves the hydrogen free to combine in other compounds as well. They were inspired by photosynthesis, a process carried out by plants. Photosynthesis is the life giving force on the earth because it is the source of all oxygen on the earth.
The new approach devised by the Weizmann team has three important steps that end in liberation of hydrogen and oxygen with the help of a special metal complex. This metal complex’s core element is ruthenium. This ’smart’ complex’s metal part and organic part help in splitting the water molecules. When water is mixed with this complex, the bonds between the hydrogen and oxygen atoms break. Here one hydrogen atom binds with organic part of the complex, the hydrogen and oxygen atoms (OH group) bind to its metal center.
The second stage is known as heat stage. Here the water solution is heated up to 100 degrees C. This releases the hydrogen gas from the complex. Here comes our clean and green source of fuel. Another OH group is added to the metal center.
Milstein explains about the magical third stage, “But the most interesting part is the third light stage. When we exposed this third complex to light at room temperature, not only was oxygen gas produced, but the metal complex also reverted back to its original state, which could be recycled for use in further reactions.”
The results are considered unique because of the generation of a bond between two oxygen atoms promoted by a man-made metal complex. It is a very unusual event. And it is still unanswerable how it can take place. The team has found out that during the third stage, light provides the energy for the two OH groups to get together to form hydrogen peroxide (H2O2). This hydrogen peroxide quickly breaks up into oxygen and water. What Milstein thinks about this chemical reaction? He says, “Because hydrogen peroxide is considered a relatively unstable molecule, scientists have always disregarded this step, deeming it implausible; but we have shown otherwise.” Another interesting thing that Milstein and his team has spotted is that the bond between the two oxygen atoms is generated within a single molecule. This bond formation doesn’t occur between oxygen atoms located on separate molecules, but it comes from a single metal center.
The greatest achievement of Milstein’s team has been the development of a mechanism for the formation of hydrogen and oxygen from water, without the need for sacrificial chemical agents. It has been achieved by using individual steps and utilizing light. For their next project, they intend to combine these stages to create a proficient catalytic system. These steps could leave a mark in the area of alternative energy.