Papers by Author: Peter Halvor Larsen

Abstract: The SOFC technology under development at Risø National Laboratory (RISØ) and Topsoe Fuel Cell A/S (TOFC) is based on an integrated approach ranging from basic materials research on single component level over development of cell and stack manufacturing technology to system studies and modelling. The effort also comprises an extensive cell and stack testing program. Systems design, development and test is pursued by TOFC in collaboration with various partners. The standard cells are thin and robust with dimensions of 12 x 12 cm2 and cell stacks are based on internal manifolding. Production of cells is being up-scaled continuously. The durability of the standard stack design with standard cells has been tested for more than 13000 hours including nine full thermal cycles with an overall voltage degradation rate of about 1% per 1000 hours. Recently, the degradation rate has been significantly reduced by introduction of improved stack component materials. 75-cell stacks in the 1+ kW power range have been tested successfully. Stacks have been delivered in a pre-reduced state to partners and tested successfully in test systems with natural gas as fuel. The consortium of TOFC and RISØ has an extended program to develop the SOFC technology all the way to a marketable product. Stack and system modelling including cost optimisation analysis is used to develop multi kW stack modules for operation in the temperature range 700-850oC. To ensure the emergence of cost-competitive solutions, a special effort is focused on larger anode-supported cells as well as a new generation of SOFCs based on porous metal supports and new electrode and electrolyte materials. The SOFC program comprises development of next generation of cells and multi stack modules for operation at lower temperature with increased durability and mechanical robustness in order to ensure long-term competitiveness.

Abstract: Extensive interfacial reactions are known to occur between Fe-Co based perovskite cathode materials and the standard solid oxide fuel cell (SOFC) yttria stabilized zirconia (YSZ) electrolyte. Thin films of gadolinia doped ceria (GDC) could be used as a diffusion barrier between the cathode and the electrolyte. The present work investigates spin coating thin diffusion reaction inhibiting films onto SOFC electrolytes. The chemical and structural evolution of ethylene glycol based precursor solution is studied by means of rheology, x-ray diffraction (XRD), high temperature XRD (HT-XRD), Fourier-transformed infrared spectroscopy (FTIR) and differential thermal analysis (DTA). The studies show that cerium formate is formed as an intermediate resin. Thin films, up to 500 nm thick, of gadolinia doped ceria (GDC) are successfully produced by multiple spin coating of polymerized ethylene glycol derived solutions on 200 1m thick YSZ tapes. The GDC and YSZ interfacial surface morphology and film thickness are studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). These films are shown to successfully prevent the creation of non-conducting reaction phases at the cathode-electrolyte interface by blocking interdiffusion.