Catalytic layers for advanced rotary alkaline water electrolysers

Hydrogen is an industrial gas mainly produced from fossil gas and other hydrocarbons. Hydrogen can also be made from water using electricity inside an electrolyser. If the power is renewable the hydrogen can be said to be renewable as well. Installation of solar and wind power is increasing rapidly. The global energy marked is changing. In periods significant energy surplus is available and the price is low. This is an enabler for energy storage and energy conversion. Electrolysers will become a key component in this regard. The investment cost of an electrolyser is important. The efficiency is key to the energy consumption and operating costs and equally important. Production from fossil sources are centralized and a distribution network of pipes, tanker trucks and bottles are in use to transport the hydrogen to the end customer. This creates logistics that increases the costs. The storage of a high volume of hydrogen waiting to be used, can in certain places be challenging from a safety perspective. Hydrogen refueling stations is an example where onsite production in certain circumstances make sense. The energy is transported to the station in the form of electric energy and used on site to split water into hydrogen and oxygen. At a refueling station the consumption of hydrogen is not constant. Some part of this variation can be smoothed out by implementing a storage solution. An electrolyser able to ramp up and down quickly and in addition able to start up and shut down repeatedly is favorable. Operating an electrolyser in this regime is challenging and this project is part of the research to understand the details in the challenges and build the fundament for the solution. The most important R&D activities in the project has been done by a postdoc at NTNU, Department of Materials, Science and Engineering. The work was mainly to characterize a selection of materials and catalytic coatings electrochemically under supergravity or artificially high gravity. The high gravity was created in a specially made centrifuge. Measurements done confirmed the positive effect of applying an artificial high gravity. The effects were tested at different levels of gravity and current density over time. This gave new knowledge about the performance under these circumstances. An effect of the project has been competence development in Nel. The contact with the research partner NTNU has given an insight in the university scientific method and key personnel has been an inspiration for behavior and best practice in R&D. All the tests done is documented and a basis for further testing and development of the design.

An effect of the project has been competence development in Nel. The contact with the research partner NTNU has given an insight in the university scientific method and key personnel has been an inspiration for behavior and best practice in R&D. An impact of the project is that Nel will pursue new projects with university partners to increase and continue the competence development. The R&D results from this project are already a part of the future market and product development strategy of Nel.

The proposed work will pursue the development of a rotary water electrolyser. Water electrolysis is a process for producing hydrogen and the by-product oxygen. Hydrogen is a valuable commodity for use in a number of industries which account for much of the current annual world sales of NOK 600 million/year of electrolysis equipment. More prominently as a fuel in an energy system based on an energy mix containing a large share of intermittent renewable energy sources (solar, wind, wave), and this is expected to double the sales by 2020. NEL aims at a 30 % share of this emerging market. A major challenge for hydrogen production via water electrolysis is energy efficiency. The energy efficiency is hampered by the very product of the process, i.e. formation of gas bubbles at the electrode surfaces. These bubbles reduce the available area for the electrochemical reaction and reduces the utilization of costly catalysts necessary for the process to reduce losses, and equally important they also introduce resistance losses in the electrolyte. A solution to this problem is to rotate the electrodes thus utilizing centrifugal forces to transport gas more efficiently away from the electrodes. The method has been demonstrated in practice, and NEL has secured exclusive rights to this novel development in water electrolysis. However, rotating electrodes will introduce new problems and uncertainties associated with catalytic layers in water electrolysis associated with the catalytic properties under super-gravity conditions and even more significantly with catalyst erosion. As very little is known about these important aspects of rotary water electrolysis we therefore propose here an investigation into these issues. The project will thus bridge the latest scientific developments with a focused industrial effort. The project targets efficiency of 4 kWh/Nm3H2 which will enable the NEL company to compete efficiently in the rapidly developing hydrogen market.