With the project ‘E2NGEL – Precious metal-free electrodes for the next generation of alkaline electrolysis’, the Institute of Technical Thermodynamics at the German Aerospace Centre (DLR) – in collaboration with industry – is making an important contribution to the implementation of the National Hydrogen Strategy. The aim of the project is to overcome a key technological and economic hurdle in hydrogen production and thus provide sustainable support for the large-scale use of alkaline electrolysis.

Importance of precious metal-free electrodes

Alkaline electrolysis is a robust technology for hydrogen production that has been established for decades. However, costs, material availability and security of supply are increasingly becoming the focus of attention for industrial ramp-up. Precious metals are a limiting factor here: they are cost-intensive, subject to high price volatility and considered critical raw materials. Replacing precious metals therefore enables a significant reduction in electrode costs while also mitigating the risks associated with these materials. When scaling electrodes and mass production, the cost and availability of the base metals used become crucially important – both for the stack and for the entire electrolyser.

Technical challenges and approach in the E2NGEL project

Previous approaches to precious metal-free electrodes have been unable to compete with precious metal-based systems in terms of efficiency, cell voltage and achievable current densities, or have shown deficits in service life. Although various coating processes have been investigated in the past, it was only within the framework of E2NGEL that it was possible to develop an overall optimised electrode concept. The decisive factor here was the targeted combination of optimised starting materials, an advanced coating process and adapted post-treatment of the electrodes. The electrode technology was developed and refined over many years at DLR and has now been implemented on an industrial scale. The details of this industrial development are available from the project partners; further technical insights were presented by Dr Karsten Lange, Rheinmetall, among others, in August as part of the ‘Energy Research Networks’ event.

Performance and long-term stability

The electrodes developed in the project show results in terms of performance and overvoltage that are comparable to published precious metal-based systems. Although literature data are only comparable to a limited extent due to different cell structures and components, the overall performance of the E2NGEL electrodes is clearly competitive. Long-term stability also meets expectations: the degradation rates observed are in the range of those described in publications on precious metal systems.

Test periods and operating experience

At DLR, individual electrodes were electrochemically tested for more than 1,000 operating hours. In addition, results from stack operation are available: McPhy presented characteristic curves after around 50 operating days, corresponding to approximately 1,200 operating hours. These results were presented at the 8th Industry Workshop Advanced Alkaline Electrolysis of IFAM Dresden, among other venues.

Contributions from project participants

The E2NGEL project is based on close and proven cooperation between research and industry along the entire value chain of alkaline electrolysis. The Institute of Technical Thermodynamics was responsible for the scientific support and the structural and electrochemical evaluation of the precious metal-free electrodes. This included the design of suitable test methods, experimental characterisation under practical conditions, and the analysis of performance characteristics, overvoltages and degradation behaviour with a particular focus on long-term stability. In addition, the DLR's electrode coating processes were further developed, and the project's most efficient hydrogen electrodes were produced at the DLR.

Targeted further development

Rheinmetall took on the material development and industrial manufacture of the electrodes. Here, both the starting materials and the coating and post-treatment processes were specifically further developed in order to realise precious metal-free electrodes with industrially relevant performance for the first time.

Operation under realistic conditions

Integration into alkaline electrolysis stacks and operation under realistic conditions took place at McPhy. The tests carried out there provided important insights into the transferability of the laboratory results to large-scale operation and the suitability of the electrodes for dynamic operating modes. The work at McPhy Germany was led by Dr Matthias Neben, and these activities have since been incorporated into John Cockerill Hydrogen.

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