| Author: | Li, Zheng |
| Title: | Modelling and optimization study of protonic ceramic electrolysis cells |
| Advisors: | Ni, Meng (BRE) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Ceramic materials Fuel cells Electrochemical sensors Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Building and Real Estate |
| Pages: | xviii, 111 pages : color illustrations |
| Language: | English |
| Abstract: | Hydrogen serves as a clean energy carrier that holds great potential for enhancing the utilization of renewable energy and driving the transition towards a zero-carbon society in the future. Protonic ceramic electrolysis cell (PCEC) is a promising electrochemical technology for achieving efficient and sustainable large-scale hydrogen production. However, the intrinsic mixed-conducting nature of the electrolyte employed in PCEC results in the occurrence of current leakage, significantly impeding the Faradaic efficiency (FE) of PCEC. Furthermore, the chemical expansion caused by the hydration reaction between the electrolyte and gas phase raises significant concerns regarding the mechanical integrity of PCECs during operation. Therefore, current leakage and chemical expansion phenomena are challenges facing the development of PCEC. Numerical models of PCEC incorporating approaches such as the machine learning techniques and design of experiments (DOE) have been developed. The influences of various parameters on the PCEC are investigated to provide a comprehensive understanding of these phenomena. The simulation results reveal an observed non-linear correlation between the current density and Faradaic efficiency (FE). An optimal of 82% is found at 0.4 A cm -2 600 °C. When the current density further increases to 0.8 A cm -2, FE and its uniformity in the PCEC are respectively reduced by 21.3% and 8.8%. While the FE shows a continuous increase with increasing anode inlet flow rate or steam fraction. The results indicate that controlling the anodic operating parameter has a greater impact on regulating the electrochemical performance and FE of PCEC compared to the cathodic operating parameter. Indicated by the DOE results, the anodic inlet steam mole fraction is identified as the most important operating parameter affecting the FE of PCEC. The optimal trade-off operating point between electrochemical performance and FE can be achieved at 0.78 A m-2, 600 °C, delivering a 12.8% performance enhancement compared to the base condition. From the modelling results, it reveals that the inclusion of chemical expansion results in a higher stress level in PCECs, accounting for more than 25% of the total stress at 600 °C. Similarly, the anode operating parameters have a greater impact on the mechanical behaviour of PCEC than the cathode operating parameters. Cathode porosity is identified as the most essential parameter to the mechanical behaviour of PCEC during the operation since increasing the cathode porosity can significantly reduce both thermal stress and chemically induced stress. Overall, the framework proposed in this work, which combines numerical modelling with other techniques, shows its power in understanding current leakage and chemical expansion in PCECs. The modelling investigations identify the important operating and structural parameters to the current leakage and chemical expansion in PCECs. Therefore, the simulation results can serve as a guide for formulating PCEC operation strategies and manufacturing designs to control or mitigate harmful phenomena during PCEC operation. The quantified description of various parameters is obtained from this study, revealing their impacts on the electrochemical performance, FE, and mechanical characteristics of PCEC. This study offers comprehensive insights into the phenomena of current leakage and chemical expansion in PCECs, providing a deeper understanding of these critical aspects. More importantly, the developed framework can help other researchers and be extended to address other problems in PCEC. |
| Rights: | All rights reserved |
| Access: | open access |
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