Discovering and Processing Proton-Conducting Perovskite Oxides for High-Performance Protonic Ceramic Fuel Cells

Protonic ceramic fuel cells (PCFCs) are up-and-coming energy conversion technologies, enabling efficient electricity generation from the chemical energy of various fuels by virtue of rapid proton transport at low-to-intermediate temperatures (300–700 ℃). However, their practical applications necessitate satisfactory core component materials (cathode and electrolyte) and manufacturing techniques to fulfill multiple requirements on catalytic activity, charge and mass transport, stability, compatibility, cost, reproducibility, etc. Despite significant advancements over the last few decades, there still needs to be more suitable cathode and electrolyte materials and manufacturing techniques due to the substantial challenges in designing multifunctional materials and dealing with complex manufacturing processes. To address these challenges, this dissertation put forward novel high-entropy design strategies for cathode and electrolyte materials and a novel manufacturing technique, of which the work can be divided into three parts.First, we discovered a novel high-entropy perovskite oxide with an outstanding electrochemical performance and a desirable thermal expansion coefficient as a cathode for high-performance PCFCs. The microstructures, phase structures, thermo-mechanical properties, charge transport properties, electrochemical performance, and operating stability were studied to assess the applicability in PCFC and give insight into the improved electrochemical performance.Then, we developed a novel high-entropy protonic ceramic electrolyte with high chemical stability and excellent proton conductivity. We investigated the corresponding microstructures, phase structures, chemical durability, hydration behavior, electrical conductivity, and thermo-mechanical properties to evaluate its feasibility as a PCFC electrolyte. Furthermore, we fabricated the single cells utilizing the high-entropy electrolyte material and demonstrated promising single-cell performance and operating stability.Finally, we developed a novel 3D printing technique for manufacturing scalable tubular PCFCs. This technique enables cost-effective and facile fabrication of PCFCs and accurately controlled microstructures. Moreover, the as-fabricated single cells were confirmed with promising performance and long-term durability.To summarize, our work demonstrated that rationally designed high-entropy perovskite oxides could be exceptional candidates with superior multi-properties for the electrolyte and cathode of high-performance PCFCs. We also verified that the as-developed 3D printing technique offers excellent potential to move PCFCs one step closer to real-world applications.