Synthesis of Ba 0.3 Ca 0.7 Co 0.8 Fe 0.2 O 3-δ composite material as novel catalytic cathode for ceria-carbonate electrolyte fuel cells

Semiconductor Electrochemistry for Clean Energy Conversion and Storage

Semiconductors and the associated methodologies applied to electrochemistry have recently grown as an emerging field in energy materials and technologies. For example, semiconductor membranes and heterostructure fuel cells are new technological trend, which differ from the traditional fuel cell electrochemistry principle employing three basic functional components: anode, electrolyte, and cathode. The electrolyte is key to the device performance by providing an ionic charge flow pathway between the anode and cathode while preventing electron passage. In contrast, semiconductors and derived heterostructures with electron (hole) conducting materials have demonstrated to be much better ionic conductors than the conventional ionic electrolytes. The energy band structure and alignment, band bending and built-in electric field are all important elements in this context to realize the necessary fuel cell functionalities. This review further extends to semiconductor-based electrochemical energy conversion and storage, describing their fundamentals and working principles, with the intention of advancing the understanding of the roles of semiconductors and energy bands in electrochemical devices for energy conversion and storage, as well as applications to meet emerging demands widely involved in energy applications, such as photocatalysis/water splitting devices, batteries and solar cells. This review provides new ideas and new solutions to problems beyond the conventional electrochemistry and presents new interdisciplinary approaches to develop clean energy conversion and storage technologies.

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Progress in Material Development for Low-Temperature Solid Oxide Fuel Cells: A Review

Solid oxide fuel cells (SOFCs) have been considered as promising candidates to tackle the need for sustainable and efficient energy conversion devices. However, the current operating temperature of SOFCs poses critical challenges relating to the costs of fabrication and materials selection. To overcome these issues, many attempts have been made by the SOFC research and manufacturing communities for lowering the operating temperature to intermediate ranges (600–800 °C) and even lower temperatures (below 600 °C). Despite the interesting success and technical advantages obtained with the low-temperature SOFC, on the other hand, the cell operation at low temperature could noticeably increase the electrolyte ohmic loss and the polarization losses of the electrode that cause a decrease in the overall cell performance and energy conversion efficiency. In addition, the electrolyte ionic conductivity exponentially decreases with a decrease in operating temperature based on the Arrhenius conduction equation for semiconductors. To address these challenges, a variety of materials and fabrication methods have been developed in the past few years which are the subject of this critical review. Therefore, this paper focuses on the recent advances in the development of new low-temperature SOFCs materials, especially low-temperature electrolytes and electrodes with improved electrochemical properties, as well as summarizing the matching current collectors and sealants for the low-temperature region. Different strategies for improving the cell efficiency, the impact of operating variables on the performance of SOFCs, and the available choice of stack designs, as well as the costing factors, operational limits, and performance prospects, have been briefly summarized in this work.

Yb₂O₃ Doped Zr0.92Y0.08O2-α(8YSZ) and Its Composite Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells

Yb³⁺ and Y³⁺ double doped ZrO₂ (8YSZ+4Yb₂O₃) samples were synthesized by a solid state reaction method. Moreover, 8YSZ+4Yb₂O₃-NaCl/KCl composites were also successfully produced at different temperatures. The 8YSZ+4Yb₂O₃, 8YSZ+4Yb₂O₃-NaCl/KCl (800 °C), and 8YSZ+4Yb₂O₃-NaCl/KCl (1000 °C) samples were characterized by x–ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that a dense composite electrolyte was formed at a low temperature of 800 °C. The maximum conductivities of 4.7 × 10⁻² S·cm⁻¹, 6.1 × 10⁻¹ S·cm⁻¹, and 3.8 × 10⁻¹ S·cm⁻¹ were achieved for the 8YSZ+4Yb₂O₃, 8YSZ+4Yb₂O₃-NaCl/KCl (800 °C), and 8YSZ+4Yb₂O₃-NaCl/KCl (1000 °C) samples at 700 °C, respectively. The logσ~log (pO₂) plot result showed that the 8YSZ+4Yb₂O₃-NaCl/KCl (800 °C) composite electrolyte is a virtually pure ionic conductor. An excellent performance of the 8YSZ+4Yb₂O₃-NaCl/KCl (800 °C) composite was obtained with a maximum power density of 364 mW·cm⁻² at 700 °C.