Helmholtz-Zentrum Berlin: Less is more: Why an economical Iridium catalyst works so well (at producing hydrogen) [View all]

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https://www.helmholtz-berlin.de/pubbin/news_seite?nid=28726&sprache=en&seitenid=1

05.12.2024
Less is more: Why an economical Iridium catalyst works so well
Iridium-based catalysts are needed to produce hydrogen using water electrolysis. Now, a team at HZB has shown that the newly developed P2X catalyst, which requires only a quarter of the Iridium, is as efficient and stable over time as the best commercial catalyst. Measurements at BESSY II have now revealed how the special chemical environment in the P2X catalyst during electrolysis promotes the oxygen evolution reaction during water splitting.

Two different Iridium-based nanocatalysts for water electrolysis were examined by a HZB-led team: A commercial benchmark catalyst (left) and the newly developed P2X catalyst (right), which is more amorphous and needs four times less Iridium. The spectroelectrochemical data show how the specific chemical environments differ in both materials and how these influence the oxygen evolution reaction. © M. van der Merwe / HZB

In the future, hydrogen will be needed in a climate-neutral energy system to store energy, as a fuel, and a raw material for the chemical industry. Ideally, it should be produced in a climate-neutral way, using electricity generated from harnessing the sun’s or wind energy, via the electrolysis of water. In that respect, Proton Exchange Membrane Water Electrolysis (PEM-WE) is currently considered a key technology. Both electrodes are coated with special electrocatalysts to accelerate the desired reaction. Iridium-based catalysts are best suited for the anode, where the sluggish oxygen evolution reaction occurs. However, iridium is one of the rarest elements on earth, and one of the major challenges is to significantly reduce the demand for this precious metal. A rough analysis (see https://doi.org/10.1002/cite.201900101) showed that to meet the world’s hydrogen demand for transport using PEM-WE technology, iridium-based anode materials should contain no more than 0.05 mgIr/cm2. The current, best commercially available catalyst made from iridium oxide contains about 40 times as much as this target value.

P2X-catalyst needs less Iridium
But new options are already in the pipeline: Within the Kopernikus P2X project, a new efficient iridium-based nanocatalyst was developed by the Heraeus Group, consisting of a thin layer of iridium oxide deposited on a nanostructured titanium dioxide support. The so-called 'P2X catalyst' requires only an extremely small amount of iridium, reducing precious metal loading substantially (four times lower than in the current best commercial material).

A team at HZB led by Dr. Raul Garcia-Diez and Prof. Dr.-Ing. Marcus Bär, together with colleagues from the ALBA synchrotron in Barcelona, have studied the P2X catalyst, which shows remarkable stability even in long-term operation, and compared its catalytic and spectroscopic signature with the benchmark commercial crystalline catalyst.

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http://dx.doi.org/10.1021/acscatal.4c03562