A new system for producing green hydrogen cheaply

What does it take to produce green hydrogen more efficiently and cheaply? Apparently, small ruthenium particles and a solar-powered system for water electrolysis. This is the solution identified by a joint team involving the Istituto Italiano di Tecnologia (Italian Institute of Technology, IIT) of Genoa, and BeDimensional S.p.A. (an IIT spin-off). The technology, developed in the context of the Joint-lab’s activities and recently published in two high-impact factor journals (Nature Communications and the Journal of the American Chemical Society) is based on a new family of electrocatalysts that could reduce the costs of green hydrogen production on an industrial scale.

Hydrogen is considered as a sustainable energy vector, alternative to fossil fuels. But not all hydrogen is the same when it comes to environmental impact. Indeed, the main way hydrogen is produced nowadays is through the methane steam reforming, a fossil fuel-based process that releases carbon dioxide (CO2) as a by-product. The hydrogen produced by this process is classified as “grey” (when CO2 is release into the atmosphere) or “blue” (when CO2 undergoes capture and geological storage). To significantly reduce emissions to zero by 2050 these processes must be replaced with more environmentally sustainable ones that deliver “green” (i.e. net-zero emissions) hydrogen. The cost of “green” hydrogen critically depends on the energy efficiency of the setup (the electrolyzer) that splits water molecules into hydrogen and oxygen.

The researchers from the joint team of this discovery have developed a new method that guarantees greater efficiency than currently known methods in the conversion of electrical energy (the energy bias exploited to split water molecules) into the chemical energy stored in the hydrogen molecules that are produced. The team has developed a concept of catalyst and have used renewable energy sources, such as the electrical energy produced by a solar panel.

The researchers used nanoparticles of ruthenium, a noble metal that is similar to platinum in its chemical behaviour but far cheaper. Ruthenium nanoparticles serve as the active phase of the electrolyser’s cathode, leading to an increased efficiency of the overall electrolyzer.

Ruthenium is a precious metal that is obtained in small quantities as a by-product of platinum extraction (30 tonnes per year, as compared to the annual production of 200 tonnes of platinum) but at a lower cost (18.5 dollars per gram as opposed to 30 dollars for platinum). The new technology involves the use of just 40 mg of ruthenium per kilowatt, in stark contrast with the extensive use of platinum (up to 1 gram per kilowatt) and iridium (between 1 and 2.5 grams per kilowatt, with iridium price being around 150 dollars per gram) that characterize proton-exchange membrane electrolysers.

By using ruthenium, the researchers at IIT and BeDimensional have improved the efficiency of alkaline electrolysers, a technology that has been used for decades due to its robustness and durability. For example, this technology was on board of the Apollo 11 capsule that brought humanity to the moon in 1969. The new family of ruthenium-based cathodes for alkaline electrolysers that has been developed is very efficient and has a long operating life, being therefore capable of reducing the production costs of green hydrogen.