High-Performance Protonic Ceramic Electrochemical Cells

Protonic ceramic electrochemical cells (PCECs) have attracted considerable attention owing to their ability to reversibly convert chemical fuels into electricity at low temperatures below 600 °C. However, extreme sintering conditions during conventional convection-based heating induce critical problems for PCECs such as nonstoichiometric electrolytes and microstructural coarsening of the electrodes, leading to performance deterioration. Therefore, we fabricated PCECs via a microwave-assisted sintering process (MW-PCEC). Owing to the ultrafast ramping rate (∼50 °C/min) with bipolar rotation and the resistive heating nature of microwave-assisted sintering, undesirable cation diffusion and grain growth were effectively suppressed, thus producing PCECs with stoichiometric electrolytes and nanostructured fuel electrodes. The MW-PCEC achieved electrochemical performance in both in fuel cell (0.85 W cm–2) and in electrolysis cell (1.88 A cm–2) modes at 600 °C (70% and 254% higher than the conventionally sintered PCEC, respectively) demonstrating the effectiveness of using an ultrafast sintering technique to fabricate high-performance PCECs

In Situ Synthesized La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ–Gd_0.1Ce_0.9O_1.95 Nanocomposite Cathodes via a Modified Sol–Gel Process for Intermediate Temperature Solid Oxide Fuel Cells

Composite cathodes comprising nanoscale powders are expected to impart with high specific surface area and triple phase boundary (TPB) density, which will lead to better performance. However, uniformly mixing nanosized heterophase powders remains a challenge due to their high surface energy and thus ease with which they agglomerate into their individual phases during the mixing and sintering processes. In this study, we successfully synthesized La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF)–Gd_0.1Ce_0.9O_1.95 (GDC) composite cathode nanoscale powders via an in situ sol–gel process. High-angle annular dark field scanning transmission electron microscopy analysis of in situ prepared LSCF–GDC composite powders revealed that both the LSCF and GDC phases were uniformly distributed with a particle size of ∼90 nm without cation intermixing. The in situ LSCF–GDC cathode sintered on a GDC electrolyte showed a low polarization resistance of 0.044 Ω cm² at 750 °C. The active TPB density and the specific two phase (LSCF/pore) boundary area of the in situ LSCF–GDC cathode were quantified via a 3D reconstruction technique, resulting in 12.7 μm^–2 and 2.9 μm^–1, respectively. These values are significantly higher as compared to reported values of other LSCF–GDC cathodes, demonstrating highly well-distributed LSCF and GDC at the nanoscale. A solid oxide fuel cell employing the in situ LSCF–GDC cathode yielded excellent power output of ∼1.2 W cm^–2 at 750 °C and high stability up to 500 h