The H2Mare flagship project funded by the Federal Ministry of Education and Research (BMBF) aims to establish a completely new type of offshore plant based on the optimal integration of an electrolyzer into a wind turbine for direct conversion of electric current. The electrolyzer uses the electricity produced by the wind turbines to split seawater into hydrogen and oxygen. Further offshore power-to-X processes are also being investigated to convert hydrogen directly into feedstock chemicals for industry using carbon dioxide from the air. The catalysts required for electrolysis are the research focus of the Electrochemical Energy, Catalysis, and Materials Science Groupat TU Berlin.
They could prove a game changer in the fight against climate change: huge wind turbine farms on the high seas. They can be installed without conflict with local residents and operated with comparatively reliable wind conditions. However, major costs are involved in routing the electricity to the coast, connecting it to the grid, and transmitting it southward. Grid connection alone can account for about one third of the total costs of an offshore wind farm (see a study published last year in the journal Nature Energy: doi.org/10.1038/s41560-020-0661-2).
One solution would be to use the electricity directly at its point of production to create green hydrogen using electrolysis. This hydrogen could then be transported ashore via pipelines or tankers and burned in engines or else converted back into electricity in fuel cells. Another possibility would be to process the hydrogen at sea into industrial chemicals like methane, methanol, and ammonia using carbon dioxide from the air or seawater. “Our research focuses on the question of the required chemical purity of seawater and the possible dissolution and corrosion processes in the electrolyzer as a result of the ion and salt content of more or even less purified seawater. Direct use of seawater is desirable in principle, but may present previously unexplored challenges for the catalysts and membranes of the electrolyzers,” explains Professor Dr. Peter Strasser, head of the Electrochemical Energy, Catalysis, and Materials Science Group at TU Berlin. A catalyst based on manganese oxide enabling electrolysis despite the salinity of seawater (mainly sodium chloride) was actually discovered as early as the 1980s. However, this proved to be uneconomical.
Switching from an acidic to an alkaline environment in the electrolyzer proved a turning point: “In acidic membrane electrolyzers, especially at the oxygen electrode, the reactive chloride ion from the sodium chloride can lead to a number of unwanted chemical side reactions in the electrolyzer, affecting both molecular hydrogen formation and lifetime. However, the same chloride ion can improve the performance of oxygen catalysts in the modern generation of alkaline membrane electrolyzers by accelerating their activation," Strasser explains. In 2018, his research group presented an alkaline seawater electrolysis cell based on nanostructured nickel-iron hydroxide layers for the anode and platinum nanoparticles for the cathode, which could be tested in operation for as much as 100 hours.
Working together with the research institutes of the German Technical and Scientific Association for Gas and Water (DVGW) and the Helmholtz Center Hereon in Geesthacht, TU Berlin is now looking to further develop the electrode materials and install a test rig for high seas operation at the Electrochemical Energy, Catalysis, and Materials Science Group. The aim is to build an entire cell stack for seawater electrolysis and operate it at one kilowatt of electrical power under realistic conditions. The robustness and durability of the materials used will play a major role. "We also want to better understand the possible effects of biofouling on the electrolyzer,” says Strasser. This involves film-like deposits of biological microorganisms in the electrolyzer. In addition, the process wastewater from the cell stack will be tested for its environmental compatibility.
The project runs until 31.03.2025 with Strasser’s research group receiving 2.48 million euros. A total of 100 million euros is available to the 35 partners participating in the H2Mare flagship project.
240 partners from science and industry are working together in the BMBF’s hydrogen flagship projects. These were launched in the spring on the basis of non-binding funding indications. Total funding will amount to over 740 million euros. This is the BMBF’s largest energy-transition research initiative to date and is intended to support Germany's entry into the hydrogen economy. The three flagship projects are the result of an ideation competition and represent a key contribution to the implementation of the national hydrogen strategy. Over a period of four years, the projects aim to dismantle existing hurdles to facilitate Germany’s switch to a hydrogen economy. The projects focus on the serial production of largescale electrolyzers (H2Giga), the production of hydrogen and reaction products at sea (H2Mare), and technologies for transporting hydrogen (TransHyDE). Professor’s Strasser’s group is also involved in H2Giga, a project that has been running for somewhat longer, with funding of approximately 3 million euros.