New Method to Obtain Water from Hydrogen and Oxygen
In a famous demonstration of chemistry in high school, a teacher first uses electricity to split liquid water into its component gases, hydrogen and oxygen. Then, by combining the two gases and lighting them with a spark, the instructor reconverted gases in water with a well audible noise.
Scientists at the University of Illinois have discovered a new way to get water, and without the pop. Not only can they obtain water from unlikely starting materials, such as alcohols, but their work may also lead to produce better catalysts and less expensive fuel cells.
Zachariah Heiden and Thomas Rauchfuss have discovered the method; they can use unconventional metal hydrides for a chemical process that is part of the process of formation of water.
A water molecule consists of two hydrogen atoms and one oxygen atom. But it is not possible to simply take two hydrogen atoms and stick with one oxygen atom. The real reaction of formation of water is a bit more complicated. To produce two molecules of water (H2O), two molecules of diatomic hydrogen (H2) must be combined with one molecule of diatomic oxygen (O2), and energy is released in the process.
This reaction (2H2 + O2 = 2H2O + Energy) has been known for two centuries, but so far no one has been run in a homogeneous solution.
This well-known reaction also describes what happens inside a hydrogen fuel cell.
In a typical fuel cell, the diatomic hydrogen gas enters one end of the cell, diatomic oxygen gas enters the other end. The hydrogen molecules lose their electrons and become positively charged through a process called oxidation, while the oxygen molecules gain four electrons and become negatively charged through a process called reduction. The negatively charged oxygen ions combine with positively charged hydrogen ions, to obtain water and release electrical energy.
The “hard side” of fuel cell is the oxygen reduction reaction, not the hydrogen oxidation reaction. “However, we have found that the new catalysts for oxygen reduction could also lead to new chemical means for hydrogen oxidation,” says Rauchfuss.
Rauchfuss and Heiden have investigated a relatively new generation of catalysts for use in oxygen reduction. Researchers have concentrated particularly in certain catalysts based on iridium. They found that the iridium complex affects both the oxidation produces alcohols, such as oxygen reduction.
“Most compounds react with hydrogen or oxygen, but this catalyst reacts with both,” says Heiden.
The new catalysts could lead to future development of hydrogen fuel cells more efficient, significantly reducing its cost.