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 supplying any external energy or using electrolyte or light. 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.
“Our work is a big leap in the field of green electrical energy source,” says Dr. Kotnala. “Our novel renewable energy source, called ‘hydroelectric cell’, is a unique manifestation of the galvanic cell.”
The splitting of water into hydronium and hydroxide ions and collecting the ions using two electrodes – silver as cathode and zinc as anode – results in voltage and current generation. While silver reduces hydronium ions and releases hydrogen gas, the hydroxide is oxidised by zinc to form zinc hydroxide.
The magnesium ferrite material pellet measuring 1 sq. inch can produce 8 mA current and 0.98 volt. According to a paper published in the International Journal of Energy Research, a 2-inch diameter of the material produces 82 mA current and 0.95 volt. “We have improved the design of the hydroelectric cell material such that a 2-inch diameter material generates 150 mA current and 0.9 V,” Dr. Kotnala says.
“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 only one week as zinc hydroxide, which forms at the anode, gets into the nanopores of magnesium ferrite and reduces its activity.”
The hydroelectric cell starts working spontaneously and produces current when a few drops of water are added.How it works
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 has been synthesised to have about 30 per cent porosity.
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.
“The hydroelectric cell starts working spontaneously and produces current when we add just a few drops of water. The cell produces current to illuminate a LED light for 15 minutes,” he says.
The team has made a 3 sq inch of magnesium ferrite material that generates 300 mA initially, which then reduces to 250 mA. “We have also made a prototype of 4 sq inch material. So we have shown in the lab that scaling up the cell is possible,” says Dr. Jyoti Shah of NPL and a co-author of the paper.
“Anyone with a furnace that works up to 1,200 degree C can produce this material. The hydroelectric cell is portable, completely safe, does not pollute the environment and is a green energy source that can potentially replace traditional ways of generating renewable energy,” says Dr. Shah.
“The energy produced by HEC can be utilized in domestic residential applications in decentralized mode at low cost,” Dr. Kotnala adds.
(CORRECTION: The post has been corrected for a factual mistake. The original version said the process of splitting water was carried out at “room temperature without using power or chemicals”. It should be: “…without supplying any external energy, or using electrolyte or light”.)