Congratulations Hendrik Bohn!
Hendrik has recently defended his PhD thesis titled “Upscaling Planar Proton-Conducting Ceramic Cells for Energy Conversion” at the Technical University of Denmark
In his work, Hendrik Bohn developed an industrially relevant tape-casting route to fabricate planar PCCs up to 12 cm x 12 cm using commercially sourced precursors.
Science Summary:
Proton-Conducting Ceramic Cells (PCCs) offer a promising route to produce strategically important, low-carbon energy vectors, such as green hydrogen and ammonia, while reducing reliance on precious metals and lowering system costs. To date, commercialisation has been limited by the lack of robust processing routes for fabricating upscaled planar PCCs. In addition, the refractory nature of barium zirconate-/cerate-based proton-conducting oxides makes it challenging to densify thin electrolyte layers while minimising the loss of volatile and essential elements, often resulting in mechanically fragile large-area cells.
In this dissertation, an industrially relevant tape casting route was developed to fabricate large-area, planar PCCs with dimensions up to 12 cm x 12 cm using exclusively commercially sourced precursors, demonstrating the scalability of the approach. Key processing challenges were identified and addressed.
First, supplier-to-supplier variations in organic additives, particularly the dispersant, were found to strongly affect slurry behaviour and downstream processing outcomes.
Second, shrinkage management during debinding and co-sintering was shown to be critical for producing crack-free cells. Notably, deliberately introducing a controlled shrinkage mismatch between the electrolyte and the Ni-based negatrode resulted in successful co-sintering.
Third, systematic optimisation through sintering aid addition and co-sintering temperature variation, combined with strategies to suppress Ba volatilisation without relying on large quantities of sacrificial powder, were further explored. These efforts led to reproducible fabrication of large-area PCCs based on six different BaCe x Zr 1-x-y-z Y y Yb z O 3-δ compositions.
A deeper investigation of the commercial ceramic powders revealed deviations from the nominal effective acceptor dopant concentration. The intrinsic hydration behaviour and conductivity contributions of the powders were analysed using pellets, indicating improved protonic conductivity with increasing Ce content and acceptor dopant concentration. However, upon integration into application-relevant half cell architectures, total conductivity decreased relative to the intrinsic pellet behaviour, with losses becoming more pronounced for Zr-rich compositions. This observation is likely attributed to interaction with the Ni-based negatrode and grain boundary-related processing challenges.
Electrochemical characterisation of a PCC with an active area of 16 cm 2 delivered a peak power density of ~0.26 W cm -2 at 650 °C in FC mode, reached ~0.27 A cm -2 at 1.3 V in EC mode, and showed a degradation rate of ~2.8 % over 1000 h. These results provide a benchmark for future optimisation efforts, which will focus on optimising cell microstructure and architecture.
The thesis will soon be available in Open Access on http://orbit.dtu.dk/
