Revolutionizing Green Hydrogen Production with Next Generation PEM Water Electrolyser Electrodes

Increasing consumption of fossil energy sources such as oil, coal and gas has led to increasing climate challenges in the world. All countries agree that good access to cheap and clean energy is crucial for the development of a sustainable world. Clean energy is energy that is made from renewable energy sources such as solar, wind and hydropower. Renewable energy is not always available in places where the energy is needed or when you need it. It must therefore be possible to store and transport renewable energy. Hydrogen has a high energy content and can be made by using renewable energy to split water into hydrogen and oxygen gas. This process is called water electrolysis, in which electric current is applied between two electrodes in contact with water. A challenge with renewable energy sources such as solar and wind is that the amount of energy available is variable. PEM water electrolysis is a technology that is well suited for converting variable renewable energy into hydrogen. It consists of a solid polymer membrane coated with catalysts on both sides and sandwiched between two electrodes. The most efficient catalysts in PEM water electrolysis are based on rare and expensive elements. In fact, the annual need of iridium is already greater than the global production. It is therefore crucial to reduce the usage of rare elements to avoid a bottleneck against the upscaling of this green technology. In the HOPE project, SINTEF and NTNU work closely together to contribute to the development of next generation PEM water electrolysis technology. The project has developed a method to produce an even microporous layer (MPL) for better utilization of catalyst material and allowing for the use of thin membranes. The project used commercial titanium powders and investigated different coating methods. The project has managed to deposit thin layers of titanium powder on 25 cm2 porous titanium plates by spray coating followed by sintering in a nitrogen-containing atmosphere. Titanium nitride is formed on the surface, and the project will continue to work on manufacturing smooth MPLs with a metallic surface after sintering. The project has further developed synthesis methods based on both sol-gel and combustion for the synthesis of phase pure yttrium ruthenate pyrochlores. Different doping elements in the pyrochlores and their importance for electrochemical performance have been investigated in the project. The PhD student in the project has been on a short exchange to Johnson & Matthey and learned how they test catalysts. The electrochemical activity of the pyrochlores is promising, but apparently shows little influence of the doping. Going forward, the project will examine the stability of the pyrochlores and the importance of the various doping elements on both conductivity and stability. The project has also worked on testing catalysts in a single cell. While iridium oxide works well, the pyrochlores have so far showed low activity and poor durability. The project will continue to work on how the high activity observed in aqueous electrochemical cells can be transferred to single cells under actual operating conditions. The project is using the final element method to develop a model to better understand the impact of various properties of the PEM water electrolysis on cell performance. The project has involved several master's students, including students from Nepal and Canada and project results have been presented at international conferences.

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Efficient water electrolysis is a requirement for implementation of green hydrogen as a renewable energy carrier. Proton Exchange Membrane Water Electrolysers (PEMWE) is well suited to be coupled with intermittent power sources such as wind and solar, and offers many advantages compared to the traditional alkaline technology. However, for efficient oxygen evolution reaction in the acidic and oxidizing environment at the anode, scarce and expensive Ir-based catalyst is the current industry standard. Limited conductivity within the catalytic layer (CL), degradation of the catalyst and deterioration of the interfaces between the porous transport layer (PTL), CL and the membrane lead to poor electrolyser performance over time. A fairly high loading of Ir-based catalyst is therefore needed in conventional systems to obtain an appreciable lifetime. The extensive use of Ir is a contributing factor to the high capital cost of PEMWE and places a limitation for the upscaling of the total capacity of installed PEMWE. For GW water electrolysis installation there is a desire to reach Ir-loadings of 50 mgIr kW-1 or less. Improved catalyst utilization, alternative catalyst materials, optimized electrode architecture and stability of the CL interfaces, and optimized PEMWE operation that maximizes performance and durability are all key aspects to lower Ir-loading in PEMWE systems and are almost exclusively investigated separately. This project will pursue all these aspects, but most importantly, we will combine them using state-of-the-art manufacturing and synthesis procedures, electrochemical modelling and novel PEMWE operation procedures. This project will arrive at a new standard for iridium utilization in PEMWE systems. The project will employ a PhD student at NTNU that will be trained in electrochemistry, fabrication and characterization of PEMWE electrodes and electrochemical modelling for optimizing electrode design and PEMWE operation.