Understanding How Water Molecules Split
Plants produce energy with the help of photosynthesis. One of the important steps of photosynthesis is splitting water into hydrogen and oxygen and release of energy in this process. Scientists are trying to duplicate this process in the laboratory for the production of energy i.e. hydrogen fuel. Hydrogen fuel is a clean and green alternative fuel. Now researchers are observing single oxygen atoms hopping on a metal oxide slab, glowing brighter here and dimmer there. This very process is helping chemists to understand how water splits into oxygen and hydrogen in a better way. This process is increasing the understanding of the chemical reaction that had previously only been talked about. This reaction will assist us in future to generate hydrogen fuel from water or to clean contaminated water.
Physicist Igor Lyubinetsky, who works at the Department of Energy’s Pacific Northwest National Laboratory, says “Oxygen and water are involved in many, many reactions, this mobility might interfere with some reactions and help others.”
The scientists are making an effort to determine the basics of how titanium dioxide splits water. This break down of water molecules is a crucial mystery which the scientists have to unravel. We need to be acquainted with the knowhow of splitting of water for many purposeful activities such as hydrogen production, breaking down pollutants, and in solar energy.
Bustling Bright Spots
Researchers are utilizing a technique called scanning tunneling microscopy to observe the splitting of water into hydrogen and oxygen with the help of titanium dioxide. This scanning tunneling microscopy technique will assist the scientists in watching the chemical reaction. They are drawing a parallel from corn fields. Researchers are imagining the surface of a slab of titanium dioxide as corn field from which rows of oxygen atoms rise from a patch of titanium atoms. The alternating oxygen and titanium rows look like stripes.
Scientists can spot some atoms and molecules that rest on the surface as bright spots. The visible oxygen atom that settles on a titanium atom is known as an “adatom”. Scientists can only observe water molecules with one condition, if they drop the temperature dramatically. At ambient temperature, water moves too fast for the method to pick them up.
Scientists started watching water’s reactions with titanium dioxide at ambient temperature. They have taken a surface coated with a few oxygen adatoms, they added water — and the adatoms started to dance. Lyubinetsky observes, “Suddenly, almost every adatom started to move back and forth along the titanium row. From theory and previous work, we expected to see this along the row.” But something different happened. The adatoms didn’t just slide up and down the stripes. They also bounced out of them and landed in others. “We saw quite unexpected things. We thought it was very strange — we saw adatoms jump over the rows,” Lyubinetsky said. “We just couldn’t explain it.”
How to explain this phenomenon? Scientists developed an explanation. They are of the view that adatoms can’t move by themselves or hop over an oxygen row. They are helped by invisible water molecules, some unseen enabler. But scientists just don’t assume things. So the team calculated how much energy it would take to move adatoms with the help of water molecules. If a water molecule settles down next to an adatom, one of the water’s hydrogen atoms can jump to the adatom, making two oxygen-hydrogen pairs complete. They called this pair hydroxyls. They act as thieves, they steal atoms from other molecules and not sparing each other! If one hydroxyl steals other’s hydrogen atom, it will turn into water molecule. The water molecule floats off, leaving behind an adatom. Half the time, that adatom is one spot over — which makes the original appear to have moved. The calculated energy necessary for these different processes fit well with the team’s experimental data.
The major breakthrough according to Lyubinetsky is that water itself can work as a catalyst. We are familiar with the fact that a catalyst is a molecule that affects the rate of a chemical reaction and remains unchanged in the procedure. He observed, “Water is required to move the adatoms around, but like a catalyst it is not consumed in the reaction. You start with water and you end with water.”
Unlocking of this water splitting process will further the use of clean and green energy for the coming generations.