A Decade of Solid Oxide Electrolysis Improvements at DTU Energy

Abstract

Solid oxide electrolysis cells (SOECs) can efficiently convert electrical energy (e.g. surplus wind power) to energy stored in fuels such as hydrogen or other synthetic fuels. Performance and durability of the SOEC has increased orders of magnitudes within the last decade. This paper presents a short review of the R&D work on SOEC single cells conducted at DTU Energy from 2005 to 2015. The SOEC improvements have involved increasing the of the oxygen electrode performance, elimination of impurities in the feed streams, optimization of processing routes, and fuel electrode structure optimization. All together, these improvements have led to a decrease in long-term degradation rate from 40 %/kh to 0.4 %/kh for steam electrolysis at -1 A/cm 2 , while the initial area specific resistance has been decreased from 0.44 cm 2 to 0.15 cm 2 at -0.5 A/cm 2 and 750 C.

Metal‐Supported Solid Oxide Electrolysis Cell with Significantly Enhanced Catalysis

“…Such a device is usually operated in the relatively high‐temperature range of 700 to 900 °C, thus resulting in a high conversion efficiency, because (a) a significant part of the required energy can be provided by external heat for an ideal HTE and (b) the electrode reaction kinetics are faster at higher temperatures . To date, extensive efforts have been devoted to the development of highly efficient SOECs and promising results have been obtained …”

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

“…a multilayer tape casting (MTC) process and lamination process was applied [14]. These four MTC layers of the tapes were cut into 16x16 cm 2 pieces and co-sintered at 1315 C [18] and then cut into 53x53 mm 2 cells. The oxygen electrode (40x40 mm 2 ) was applied by screen-printing and sintered at 930 C.…”

“…The justification of including this contribution upon CNLS fitting of the experimental IS is based on previous work e.g. with SOC having different support layer microstructures [18]. Figure 6 shows the fuel electrode/electrolyte interface for Cell A and Cell C after electrolysis testing for 1000 h and 2000 h, respectively.…”

Co-electrolysis of CO2 and H2O in high-temperature solid oxide electrolysis cells: Recent advance in cathodes

“…Because the Ni-based cathode exhibits porous structure, high electronic conductivity, appropriate catalytic activity and close thermal expansion coefficient (TEC) with the electrolyte, it could act as an excellent SOECs cathode for CO 2 /H 2 O co-electrolysis, and thus has drawn intense corresponding studies [37,[47][48][49][50] . Mogensen and co-workers have evaluated the performance, reaction mechanism and the durability of Ni-cermets cathodes for CO 2 /H 2 O co-electrolysis in single SOEC or SOEC stacks for decades [7,15,24,25,29,30,48,51,52] . It has been demonstrated that the Ni-cermets cathodes indeed display a high catalytic activity for CO 2 /H 2 O co-electrolysis.…”