Nanostructure technology gives hydrogen energy a boost
Hydrogen is a promising clean energy source. It is best obtained through electrolytic water splitting, using electricity to split water into hydrogen and oxygen. When driven by renewable energies, hydrogen can be obtained at net zero emissions – so-called ‘green hydrogen’. Fundamental to this process is hydrogen evolution reaction (HER) electrocatalysts, materials that help the reaction. Due to its high catalytic activity, platinum is the most popular and widely used HER electrocatalyst. But it is expensive and scarce, presenting an obstacle to its use in industrial applications. The HyCat project, supported by the European Research Council, has developed an innovative nanostructure that aims to reduce the quantity of platinum needed in the reaction and could bring costs down. “The key aim of this project is to develop a novel and performant electrocatalyst to produce hydrogen through the electrochemical water splitting reaction,” says Liberato Manna, senior researcher at the Italian Institute of Technology and HyCat project coordinator.
Creating a nanostructure electrocatalyst system
To make the new electrocatalyst, the researchers first immerse a current collector made of titanium in a chemical bath that contains copper and other reagents. This causes copper oxide to grow on the surface of the titanium in vertically orientated nanoplates. These nanoplates – in essence “the rust of copper,” says Manna – are transformed into highly electrically conductive metallic copper, by running a reducing voltage to the underlying current collector. Finally, still applying the reducing voltage, a solution including platinum salt is added, which decorates the copper nanostructures with platinum nanoparticles. “This complex procedure yields a cathode characterised by mechanical and chemical stability and especially allows for an optimal dispersion of platinum nanoparticles,” explains Manna. “This maximises its area, therefore minimising its use and the overall cost of the technology,” he says.
Running trials of the new electrocatalyst
Through the project, the HyCat team ran hundreds of experiments, to find the optimal solution for a series of parameters. The expensive platinum could be replaced by a far cheaper ruthenium (another platinum-group metal), at around a third of the cost. The average amount of ruthenium on the electrode was as low as 53 μg/cm2, 10 times lower than the platinum used in other state-of-the-art electrolysers. “Our optimised cathode is competitive, in terms of performance,” remarks Manna. “When assembled in a single cell, our technology goes beyond the current state of the art,” he adds. If implemented in a 1 MW H2 plant, the system yields a production cost of around USD 2.26/kg of hydrogen – in line with the green hydrogen target cost set by the European Commission for 2030 of less than USD 2.50/kg.
Technology scale-up
The next step for the project is to further expand the electrode to a practical size of around 100 cm2. Around this scale, the electrolyser will become practically useful for producing hydrogen for on-site use, reaching kW-scale power generation. With a 2.5 kW electrolyser, for example, it is possible to produce around 1 kg of hydrogen per day, enough to power a house. “A further study will be carried out based on the performance data acquired on this electrolyser to provide an in-depth prospect for building MW-scale hydrogen plants using our electrocatalysts for massive-scale production,” says Manna.
Keywords
HyCat, nanostructure, copper, platinum, cathode, hydrogen, water, splitting, green, energy