On the move with green hydrogen

The Indian Railways recently announced that a hydrogen-powered train, developed at the Integral Coach Factory in Chennai, has successfully completed all tests. This is a welcome sign of progress for the National Green Hydrogen Mission, which aims to produce at least five million metric tonnes of green hydrogen per year by the year 2030, a milestone on the way to achieving nationwide net zero emissions by 2070.

The train will soon be carrying passengers between Jind and Sonipat on an 89-km route in Haryana. This project will rely on hydrogen produced in Jind by a 1-MW polymer electrolyte membrane electrolyser that produces 430 kg of hydrogen every day. The hydrogen will refill fuel tanks on the train, where fuel cells will convert the hydrogen to electricity that runs the train’s electric motors.

The principle is quite simple. An electrolyser splits a water molecule into oxygen, protons, and electrons. In an electrochemical reaction at the negative electrode (called the anode), molecular oxygen is released, and the electrons liberated are conducted to the cathode via an external circuit. The polymer electrolyte membrane between the cathode and the anode is selective and only allows protons to pass through to the cathode, where they unite with the electrons to form hydrogen molecules. These rise as a gas and are collected, compressed, and stored. The membrane, typically a fluoropolymer such as Nafion (related to Teflon) is an excellent insulator, and electrons will not pass. The hydrogen and oxygen formed are clearly separated.

In the locomotive, as in a hydrogen-powered automobile, the above reaction is reversed in the hydrogen fuel cell. Hydrogen is brought to the anode, where each molecule is catalytically split into two protons and two electrons. The protons pass through the membrane to the cathode, where they meet oxygen in air and the electrons that are brought through an external circuit from the anode. Water is formed. The electrons flowing through the external circuit constitute the electric current that powers the locomotive.

There is a key difference between the chemical reactions in the fuel cell and in the  electrolyser. The chemistry between hydrogen and oxygen is spontaneous, a reaction waiting to happen. Water, however, will not split into the two elements by itself. Electrical current must be supplied to provide the energy for this electrochemical reaction.

To produce green hydrogen, the electricity for the electrolysers has to come from renewable sources, such as solar panels or wind turbines. New sources of renewable energy will be needed to meet the goals of the National Green Hydrogen Mission. Also under way are exciting attempts to produce hydrogen in microbial electrolytic cells, where electrochemically active microbes grow on anodes and oxidize organic matter — agricultural residues, even wastewater — and pass the electrons generated to the anode (Current Science, vol. 128, p. 133, 2025).

The catalysis steps require expensive materials such as platinum, iridium, etc. Ongoing research is aimed at replacing these with inexpensive nickel, cobalt, or even iron. In early work towards cheap hydrogen generation, the group of C.N.R. Rao at the Jawaharlal Nehru Centre for Advanced Scientific Research designed nickel-nickel hydroxide-graphite electrodes with a water-splitting capability comparable to platinum electrodes (Proc. Natl. Acad. Sci., USA, vol. 114, 2017). Combining such developments with solar, and microbe-driven processes can produce a fuel that is both green and inexpensive.

The article was written in collaboration with Sushil Chandani [email protected]