R K Kotnala & his PhD student Jyoti Shah
CSIR-National Physical Laboratory, New Delhi
For several decades now, scientists have been attempting to find that ideal source of energy that is clean as well as renewable. It has led them to harness the energy of the sun, wind and nuclear power. All of these have already been deployed, though each of them has major shortcomings: sun or wind is not always available, while nuclear energy requires complicated and heavy engineering and carries with it the risk of radiation.
There has also been an ongoing effort to draw energy from water, one of the most easily available cheap resources. The force of running or falling water has been utilised to produce electricity but this is not a readily available resource and it requires heavy engineering too.
Scientists have tried to ionise water, break it into its constituent hydronium (H3O+) and hydroxide (OH-) ions, so that the hydronium ion, nothing but a proton, can be made to conduct electricity. But this has so far been possible only under special laboratory conditions. High positive free energy of water molecule needs either high temperature to dissociate it or, ideally, 1.23 volt potential to break it down at room temperature. But the conductivity of pure water is very poor, at 0.055 micro siemens per cm, so the reaction is very slow. It can generate current only in the order of micro amperes.
Kotnala’s team at CSIR-National Physical Laboratory, New Delhi, has been able to come up with a big breakthrough in this field. They have not just been able to ionise water in normal room conditions, but have also manufactured a cell that produces appreciable amounts of electricity when dipped in water or even when water is soaked by it. The invented prototype “hydroelectric cell” (HEC) requires just a few millilitres of water to generate up to 82 milli amperes of current, enough to light up a few LEDs or even run a miniature plastic fan; its maximum power output is 74 milliwatt.
The invented HEC dissociates water molecule at room temperature without any external energy supply, thanks to the use of specially manufactured material from magnesium ferrite in which nano-pores were drilled. Unsaturated surface cations (negative ions) and oxygen vacancies created in magnesium ferrite provides enough surface energy and electric field inside nano-pores to break the water molecule at room temperature.
Broken hydronium and hydroxyl ions are transported through the surface and capillary diffusion in the porous network. Zinc and silver were used as the two electrodes in the cell. The hydronium (H3O+) ions are reduced at inert silver electrode to release hydrogen gas, while the hydroxide (OH-) ions are oxidised at the Zinc electrode to form zinc hydroxide. Neither hydrogen gas nor zinc hydroxide pollutes the environment in the manner that fossil fuels do. In fact, they can be put to a variety of uses to get collateral benefit from this cell.
The HEC opens up an exciting new possibility of deriving green energy from relatively small amounts of standing or still water. Further research is required to scale up the cell to enable it for use for everyday purposes.