Ha-Ni Im

Spatial Distribution of Oxygen Chemical Potential under Potential Gradients and Theoretical Maximum Power Density with 8YSZ Electrolyte.

The maximum power density of SOFC with 8YSZ electrolyte as the function of thickness was calculated by integrating partial conductivities of charge carriers under various DC bias conditions at a fixed oxygen chemical potential gradient at both sides of the electrolyte. The partial conductivities were successfully taken using the Hebb-Wagner polarization method as a function of temperature and oxygen partial pressure, and the spatial distribution of oxygen partial pressure across the electrolyte was calculated based on Choudhury and Patterson’s model by considering zero electrode polarization. At positive voltage conditions corresponding to SOFC and SOEC, the high conductivity region was expanded, but at negative cell voltage condition, the low conductivity region near n-type to p-type transition was expanded. In addition, the maximum power density calculated from the current-voltage characteristic showed approximately 5.76 W/cm2 at 700 oC with 10 μm thick-8YSZ, while the oxygen partial pressure of the cathode and anode sides maintained ≈0.21 and 10−22 atm.

Hydration of Proton-conducting BaCe 0.9 Y 0.1 O 3−δ by Decoupled Mass Transport

Mass relaxation profile of a perovskite-type oxide, BaCe0.9Y0.1O3−δ, was studied to understand decoupled diffusion of oxygen and hydrogen species during hydration/dehydration. The mass relaxation measurements are performed by thermogravimetric analysis (TGA) under various humidity conditions (Dry, −3.0 ≤ log(pH2O/atm) ≤ −1.6) at a constant oxygen partial pressure (log(pO2/atm) = −1.00 ± 0.01). The decoupled ions participated in hydration/dehydration reactions were proven to be at different ratios from the result introduced by the 8Rm function. The enthalpy and entropy of non-stoichiometric hydration reaction, which considers each ratio of charge-carrier species, were −144.7 ± 3.7 kJ/mol and −147.8 ± 3.2 J/mol · K, respectively.

Solvothermal synthesis of high hydrogen permeable Pd/Ag alloy particles and their hydrogen transport properties

Pd76Ag24 nanoparticles with high purity and a face-centered cubic structure were prepared using a solvothermal method. The lattice parameter of the Pd77Ag23 nanopowders (space group 225Fm3m) was calculated to be a = 3.9382 Å. The primary particle size was calculated to be 7.7 nm from the X-ray line width using the Scherrer formula, and the interplanar distances was estimated to be 2.272 and 2.000 Å based on indexing on the (111) and (200) plane, respectively. These values are slightly larger than those of pure Pd and smaller than Ag in the (111) plane. The linear relationship of the hydrogen permeation flux with the square root of the hydrogen partial pressure gradient across a 0.26-mm-thick Pd/Ag-YSZ cermet membrane confirmed the major hydrogen transport through the Pd/Ag phase of cermet membranes. The Pd/Ag-YSZ cermet membranes showed significantly higher hydrogen permeation flux than the Pd-YSZ cermet membrane, even though the activation energy for the Pd/Ag alloy cermet membranes showed slightly higher values than that of the Pd cermet membranes. The hydrogen–oxygen dual flux through Pd/Ag-YSZ cermet membranes was confirmed by the maximum hydrogen production by combining the ability of hydrogen production from water with the function of hydrogen separation on composite membranes