A team from the Korea Institute of Energy Research (KIER) led by Dr. Kyung-Su Kang and Dr. Hyun-Joon Lee has created nickel- and cobalt-based electrodes for water electrolysis. The work was published in the journal Advanced Science.
Water electrolysis is an environmentally friendly way to produce hydrogen by splitting water under the action of electricity. Alkaline electrolysis (splitting in an alkaline medium) is convenient for large-scale production because the equipment is relatively inexpensive. But the rate of hydrogen evolution under alkaline conditions is more than 100 times lower than under acidic conditions, so expensive catalysts - platinum or ruthenium - are used to speed up the reaction. Their price (about 58 and 54 dollars per gram respectively) complicates mass production.
The new electrode combines two components on its surface: nickel oxide, which speeds up water splitting (the key stage of the process), and a nickel-cobalt alloy, which promotes hydrogen evolution. This structure, called a heterostructure (that is, consisting of different materials joined together), made it possible to accelerate the reaction.
Laboratory tests showed that the new electrode delivers the same rate of hydrogen production as a platinum one but requires about 40% of the overpotential - the additional voltage needed to start the reaction. This is one of the best results among non-noble electrodes in the past three years. The cost of the new electrode's materials is about 0.02 dollars per gram of nickel and 0.05 dollars per gram of cobalt, which is 99% cheaper than platinum and ruthenium.
The technology was also tested outside the laboratory. A cell 8.7 cm in diameter with the new electrode showed a voltage 11% lower than that of a standard nickel cell. After 600 on-off cycles, performance remained stable, which is important for working with intermittent renewable energy sources such as sun or wind.
"Our study proves that electrodes without precious metals can achieve world-class efficiency and durability in alkaline water electrolysis. This will make it possible to reduce dependence on imported materials and, in the future, lower the cost of green hydrogen," Dr. Kang noted. His colleague Dr. Lee added that the scientists have already made electrodes 40 cm in diameter, confirming the possibility of scaling up, and are now optimizing the process for mass production. The plans include increasing the electrode area to 5,000 square centimeters for use in megawatt-scale electrolysis systems.