Metal supported proton conducting electrolyser cell for renewable hydrogen production

High temperature electrolysis (HTE) of steam offers higher efficiency of conversion of renewables and peak electricity to H2 than alternative low temperature electrolysis when coupled to an external renewable heat source from solar or geothermal plants (typically supplied in the temperature range 200-600°C). HTE technology developed to date is based on solid oxide electrolyser cells (SOECs) with oxide ion conducting electrolytes - in effect reversed SOFCs - operating at 700-1000°C, which require additional heating of steam. In the METALLICA project, development of HTE technology based on novel alloy- supported proton conducting electrolytes operating at 600°C for efficient use of heat and steam supplied by geothermal, solar, or waste energy from industrial plants has been the focus. Another benefit compared to an SOEC cell is the production of dry hydrogen. SINTEF and UiO is developing of high-temperature proton ceramic electrolysis cells (PCEC) with a very thin proton conducting electrolyte BZY (BaZr0.85Y0.15O3) deposited by the thin film fabrication methode Pulsed Laser Depositon (PLD). Thin film functional layers as well as the metal supported cell geometry allow for reduced operating temperature, ~600 °C. The main challenges in terms of fabrication of metal supported cells have been associated to the restrictions in sintering temperature and atmosphere induced by the metal support, as well as strict demands on the roughness of substrates used for PLD. In METALLICA, metal supports for planar MS-PCEC were manufactured using tape-casting of low-cost ferritic stainless steel. A coating protecting the metal support against oxidation was applied and a conducting buffer layer of La0.5Sr0.5Ti0.75Ni0.25O3-d (LSTN) was further deposited to smoothen the surface before the deposition of thin functional layers. Both BaZr0.85Y0.15O3-NiO (BZY15-NiO) cathode and the BaZr0.85Y0.15O3 (BZY15) electrolyte were applied by PLD at 700 °C and 600 °C substrate temperatures respectively. Electrochemical testing performed in the project showed a higher cell resistance, indicating that cell improvements are needed. To our knowledge, this is the first time metal supported electrolysis cells based on proton conducting oxides have been made, and through this work important advances in using metal supports and thin films in planar PCEC assemblies have been made.

The METALLICA project aims at developing new knowledge and cutting edge solutions to achieve sustainable integration of high temperature steam electrolysis technology in geothermal or solar plants by exploiting the international leading expertise of Norwe gian's academia and research institutes in protonic ceramics. The METALLICA project will develop a clean technology based on novel alloy supported proton conducting electrolytes (PCEC) operating at 600°C for efficient use of heat and steam supplied by geo thermal or solar plants. Proof-of-concept of co-electrolysis of steam and CO2 will also be demonstrated as a further pathway for integration of PCEC in industrial processes. The robust cells will be produced by a combined process developed at SINTEF and U iO making use of wet ceramic processing for producing alloy sustrates and side electrodes, and pulse laser deposition for low temperature deposition of dense cristalline electrolytes. In collaboration with international partners, the scalability of this p rocess will be demonstrated in a two-step approach with firstly the production of button cells with non-optimized electrodes and secondly the realization of 6 x 6 cm2 cells with optimized components using a novel powerful PLD recently acquired at SINTEF. Testing of these cells will be carried out to guide materials, microstructures and architectures optimization, and to determine rate limiting steps as function of cell's operating parameters. This pioneering work will open new scientifical and technologic al pathways for sound management of renewable sources and deployment of protonics technology with innovative SMEs. The project is coordinated by Dr. Marie-Laure Fontaine at SINTEF with support from UiO. It trains one post-doc at UiO, lasts 3 years and h as a budget of 12.8 MNOK.