Rapidly Direct Laser 3D Printing of High-Performance Protonic Ceramic Fuel Cells

Abstract

Fuel cells with a dense ionic conducting electrolyte layer sandwiched between two porous electrode layers are one of the most efficient fuel-to-electricity energy conversion devices. Their reversible operation can also efficiently electrolyze water to hydrogen, reduce carbon dioxide to fuels, synthesize ammonia, upgrade fuels, and store energy on large scales. Compared with the popular low-temperature (~80 oC) proton exchange/polymer electrolyte membrane fuel cells and the high-temperature (700-1000 oC) oxygen ion-conducting solid oxide fuel cells (SOFCs), initially used in electric vehicles, auxiliary powers, power plants, and hydrogen electrolyzers, the rising star of protonic ceramic fuel cells (PCFCs) based on proton conducting oxide electrolytes offers excellent suitability for operating at 400-700 oC, the optimum temperature range for electrochemical energy devices, enabling extensive superiorities (high efficiency and performance, long thermal and chemical stabilities, flexible fuels, and cost-effective compatible materials) compared to their counterparts. In recent ten years, many high-performance PCFCs have been reported. However, most performances were achieved using small-area button cells (<0.5cm2) fabricated using spin coating, drop coating, manual brushing, and screen printing of electrolytes on the dry-pressed anode supports, followed by co-firing. There are challenges to transferring the excellent microstructures and materials chemistries/properties obtained from small-area cells to large-area cells and stacks. Furthermore, the decrease in cell component layer thickness for high volumetric cell performance and the requirement for more efficient, faster, and more cost-effective manufacturing motivated the advanced manufacturing of PCFCs. This work will focus on the direct laser 3D printing (DL3DP) of PCFCs performed at Clemson University. The DL3DP integrated 3D printing (microextrusion and ultrasonic spraying) and laser processing (drying, sintering, and machining), allowing for manufacturing PCFC components, single cells, and stacks with the desired microstructures and geometries irrelevant to the area. The DL3DP could rapidly and cost-effectively manufacture PCFCs without conventional long-term furnace processing. The processing speed could be 2 orders of magnitude faster than the conventional tape-casting and furnace co-firing method. The achieved cells and stacks showed excellent fuel cell performance and less dependence on the effective area. The cells showed peak power densities 1.6-2.6 times that of the conventionally processed samples. The stacks demonstrated a peak power of 7 W and constant power outputs of 0.5-3.1 W for 110-260 hours. This DL3DP can be expanded to manufacturing other heterogeneous ceramics for energy conversion and storage devices. Figure 1