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Heraeus and Sibanye-Stillwater develop ruthenium-based catalyst

Published by , Editorial Assistant
Global Hydrogen Review,

Heraeus and Sibanye-Stillwater have developed a pivotal innovation in electrocatalysts for hydrogen production: a new and stable ruthenium-based catalyst for proton exchange membrane (PEM) water electrolysis. This breakthrough significantly improves the sustainability of hydrogen production by greatly reducing material cost and the reliance on iridium, a highly scarce and expensive resource.

Hydrogen has emerged as a fundamental element in the energy transition, with, according to the Hydrogen Council, announced capacities of 175 GW expected by 2030. Notably, 40% of this future capacity is expected to be produced using PEM electrolysis, a technology dependent on iridium, an element in extremely limited supply. With only about nine metric t of iridium mined annually and widespread utilisation in various industries, supply bottlenecks are imminent – unless solutions are implemented that reduce the amount of iridium used in the PEM application.

Currently, approximately 400 kg of iridium is required to build one GW of capacity. A reduction to less than 100 kg/GW is necessary to avoid supply bottlenecks. Heraeus' latest innovation in collaboration with Sibanye-Stillwater presents a solution: a ruthenium-based catalyst that can enable an 85% saving on iridium compared to an iridium oxide catalyst, alleviating the potential supply concerns. Primary production of ruthenium is 3.5 times that of iridium.

Alongside iridium, ruthenium also catalyses the oxygen evolution reaction (OER), which is the critical stage in PEM electrolysis. Ruthenium possesses superior catalytic activity to iridium but lacks stability in the challenging conditions of a PEM electrolyser stack. The Heraeus concept solves this problem by combining both ruthenium and iridium oxide in a novel manner, enhancing stability, while maintaining the increased catalytic activity provided by ruthenium.

This ruthenium-iridium oxide material class delivers an unprecedented activity boost. The catalyst can achieve up to 50 times higher mass activity than iridium oxide, and unlike ruthenium oxide alone, it remains stable in operational conditions. Accelerated degradation tests confirmed its stability after 30 000 cycles, presenting activity loss significantly lower than for ruthenium oxide and on par with iridium oxide. These findings were verified by Mattiq, a start-up based in Chicago, US, which combined industry expertise in chemistry and materials science and performed high throughput screening experiments for the development project.

By including ruthenium, Heraeus not only helps mitigate potential supply bottlenecks, but also brings significant commercial benefits. By implementing this breakthrough, a significant 90% reduction in CAPEX on material costs can be achieved, ensuring hydrogen production becomes more economically feasible and efficient.

Dr. Philipp Walter, EVP New Business Development at Heraeus Precious Metals stated: “The dramatic reduction in CAPEX needed per GW enabled by our new ruthenium-based catalyst not only addresses the iridium supply problem, but also makes economic sense. It is solutions like these that will champion the necessary scale-up of the hydrogen industry, bringing us closer to achieving our global green energy goals.”

Neal Froneman, CEO of Sibanye-Stillwater commented: “As the largest producer of primary iridium globally, we firmly believe that sustainable demand of these metals, with supply in mind, is beneficial for the entire industry. The commendable progress achieved by Heraeus in their work to date is encouraging, and we highly value our partnership in this endeavour.”

In its product portfolio for the hydrogen economy, Heraeus already offers another iridium-saving catalyst based on iridium oxide on a carrier.

“We recognise that different operational settings may require different solutions; one catalyst may perform better under unique conditions, while another catalyst could be more suitable under other operation boundaries,” said Christian Gebauer, Head of R&D Hydrogen Systems at Heraeus Precious Metals. “The beauty of these two catalysts is their potential to further reduce the iridium content in the application. Our long-term outlook is to develop solutions that ultimately reduce iridium content to a mere 15 kg/GW. These advancements will open the doors for hyperscaling beyond 2030 and represent a significant stride in enabling a sustainable hydrogen industry and strengthening the future of green energy.”

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