We investigated the effect of electrolyte thickness and operating temperature on the heat and mass transfer characteristics of solid oxide fuel cells. We conducted extensive numerical simulations to analyze single cell performance of a planar solid oxide fuel cell (SOFC) with electrolyte thicknesses from 80 to 100 μm and operating temperatures between 700 °C and 800 °C. The commercial computational fluid dynamics (CFD) code was utilized to simulate the transport behavior and electrochemical reactions. As expected, the maximum power density increased with decreasing electrolyte thickness, and the difference became significant when the current density increased among different electrolyte thicknesses at a fixed temperature. Thinner electrolytes are beneficial for volumetric power density due to lower ohmic loss. Moreover, the SOFC performance enhanced with increasing operating temperature, which substantially changed the reaction rate along the channel direction. This study can be used to help design SOFC stacks to achieve enhanced heat and mass transfer during operation.

Anode-supported solid oxide fuel cells (SOFCs) model based on artificial neural network (ANN) and optimized design variables were modeled. The input parameters of the anode-supported SOFC model developed in this study are as follows: current density, temperature, electrolyte thickness, anode thickness, anode porosity, and cathode thickness. Voltage was estimated from the SOFC model with the input parameters. Numerical results show that the SOFC model constructed in this study can represent the actual SOFC characteristics very well. There are four design parameters to be optimized: electrolyte, anode, cathode thickness, and anode porosity. To derive the optimal combination of the design parameters, we have used a multi-armed bandit algorithm (MAB), and developed a methodology for deriving near-optimal parameter set without searching for all possible parameter sets.

State-of-the-art micro-solid oxide fuel cells (micro-SOFCs) use ion-conducting ceramic electrolytes with thicknesses in the tens to hundreds of nanometers scale, which enabled a drastic decrease in operating temperature without a decrease in cell performance. Here, we present a self-supporting ceramic electrolyte membrane with only 10 nm thickness as a potential platform for the in situ study of nanoionics under fuel cell operating conditions. The challenge lies in the handling of the fragile membrane during the cell fabrication and during the cell operation. The mechanical strength of the ceramic electrolyte membrane was improved by configuring the membrane as a bi-layer structure, where both layers are the same materials with a few nanometers thickness. The bi-layer structure generated the difference in electrolyte microstructures and further reduced the grain sizes of the electrolyte. The cell showed a high open-circuit voltage of 1.05 V and was stable for the entire 14 hours of measurement time, which proved the functionality of the extremely thin electrolyte for micro-SOFCs.

The present study established the two-dimensional axisymmetric model for a freestanding circular cell of the low-temperature micro-solid oxide fuel cell (µ-SOFC) that is composed of platinum (Pt) electrodes and a yttria-stabilized zirconia (YSZ) electrolyte. The only membrane electrode assembly (MEA) was constructed for the numerical simulation in order to avoid the meshing problem with a very high aspect ratio of the submicron layers. We considered the charge and species conservation equations and electrode kinetics to elucidate the intricate phenomena inside the µ-SOFC. The extensive numerical simulations were carried out by using the commercial code to predict the effect of operating temperature and electrolyte thickness on the electrochemical performance of µ-SOFC. Our numerical model was calibrated with the results from experiments, and we provided the average cell current density and overpotentials with respect to the electrolyte thickness and the operating temperature. It was found that the electrochemical performance increased with the increase in operating temperature, owing to both rapid electrochemical reactions and ionic conduction, even in µ-SOFC. Moreover, the major voltage loss of µ-SOFC at low-temperature was caused by the cathodic activation overpotential.