| Popis: |
Climate change and environmental degradation, in addition to the challenges of limited fossil fuel resources, have driven governments to pursue creative renewable energy sources. Natural gas and biofuels are limitless energy sources produced from both fossil fuels and biomass that is renewable. SOFCs (Solid Oxide Fuel Cells) are a type of renewable energy system that can convert biofuels into power and heat whenever needed. They often operate at high temperatures (> 850 °C), which allows for fuel flexibility; nevertheless, such high temperatures are associated by rapid material deterioration and performance loss, usually before 40,000 hours of operation. As a result, many recent studies and activities have concentrated on lowering the operating temperature of SOFCs. Lowering the temperature causes decreased ionic conductivity, decreased catalytic activity, and increased carbon deposition on the anode side catalysts. This project aimed at developing an innovative cathode-supported SOFC to be fed by biofuels and operating at low-intermediate temperatures. Colloidal processes and co-sintering were selected to fabricate the final SOFC owing to their flexibility in optimizing the final desired properties and saving more manufacturing costs. The first chapter of this thesis provides an introduction to the essential concepts as well as professional specifics and previous work. The cell design and component materials are defined, as are additional requirements for lowering the operating temperature in SOFCs. Commercialization challenges and recommended solutions are also discussed, which involve the development of both new anode materials and production procedures. The project's goal is detailed at the end of Chapter 1, along with the reasons why various approaches were chosen. Molybdenum was chosen as a suitable anodic material to be doped into LSCF, and tape casting was developed further to create the cathode. The cathode support layer should have a consistent thickness, balanced flexibility and mechanical strength, and better shrinkage qualities. The plasticizer is a high molecular weight polyethylene glycol (PEG 4000), which improves these characteristics. Chapter 2 covers the steps involved in creating the button SOFC, starting with powder synthesis and ending with cathode tape casting. SOFC performance and anode catalytic activity are investigated to assess SOFC durability while fed by biogas. In Chapter 3, the findings are presented and explored in various contexts. Meanwhile, the anode material performance and cathode design and structure receive the greatest attention. Molybdenum was doped into LSCF via auto-combustion, yielding a fine and porous powder form. X-ray diffraction patterns demonstrated that increasing the Mo dopant increases anodic stability. In parallel, flat and crack-free green cathodes with 47% solid loading can be obtained by adjusting the PEG 4000 to binder quantity ratio at 1.00 wt% and drying the tapes at 70% relative humidity. The tapes had an excellent mechanical strength to flexibility ratio, which allowed them to be readily handled and rolled. The tapes benefited from a strong balance of flexibility and mechanical strength, allowing them to be easily handled and rolled while also exhibiting very low residual stresses during subsequent lamination and co-sintering procedures. The final manufactured SOFC revealed a porous anode structure and a less porous cathode layer using electron microscopy. Whereas the electrolyte was dense enough to ensure gas tightness. There was no delamination throughout the cell. The cells were then electrochemically measured, and the reactivity of LSCFMo to various fuels and temperatures was investigated. LSCFMo performed best when fed by methanol at 700 °C, leaving no carbon traces after operation. The very low ohmic resistance of the electrodes indicates a very good design and manufacture technique. A conclusion is presented in the final section of this thesis to highlight the most significant achievements of this research. |
