In a major breakthrough, scientists at Delhi’s National Physical Laboratory (NPL) have developed a novel way of producing electricity from water at room temperature without using any power or chemicals. A team led by Dr. R.K. Kotnala used nanoporous magnesium ferrite to split water into hydronium (H3O) and hydroxide (OH) ions and used silver and zinc as electrodes to make a cell that produces electricity.
The hydroelectric cell that uses magnesium ferrite of 1 sq. inch size produces 8 mA current and 0.98 volt. According to a paper published in the International Journal of Energy Research, magnesium ferrite of 2-inch diameter produces 82 mA current and 0.9 volt. Now, the hydroelectric cell material design has been improved and a 2-inch diameter material generates 150 mA current and 0.9 V.
“When we connect four cells [of 2-inch diameter] in series the voltage increases to 3.70 volts and we can operate a small plastic fan or a LED light of 1 watt,” says Dr. Kotnala, the senior author of the paper.
“At a stretch, we can operate the LED for one week as zinc hydroxide, which forms at the anode, gets into the nanopores of magnesium ferrite and reduces its activity.”
Since magnesium has high affinity for hydroxide, it spontaneously splits or dissociates water into hydronium and hydroxide ions. The hydronium ions get trapped inside the nanopores of magnesium ferrite and generate an electric field. The electric field helps in further dissociation of water.
Magnesium ferrite is made as an oxygen-deficient material and has plenty of oxygen vacancies.
To further enhance the activity of magnesium ferrite, about 20 per cent of magnesium is replaced with lithium. The substitution of lithium at magnesium site increases the sensitivity of magnesium ferrite. This is helpful in dissociating water at room temperature as the electrons get trapped in the oxygen deficient sites.
“Because electrons are trapped in the oxygen vacancies they attract water molecules towards the surface of magnesium ferrite. Only when water molecule is brought very close to the magnesium atom can magnesium have any affinity with hydroxide and start the dissociation process,” he says.
Published - October 17, 2016 11:40 pm IST
