Advances and perspectives on solid oxide fuel cells : From nanotechnology to power electronics devices

Solid oxide fuel cells (SOFCs) hold an important place in energy conversion and storage systems due to their fuel flexibility, high efficiency, and environmental sustainability. The scorching temperature (≥800 °C) to operate SOFCs results in shorter life span due to rapid deterioration of accompanying components. Nanomaterials have attained considerable attention in recent years due to their great technological importance in fuel cell technology. Nanoengineering of the architectures of known materials and adopting composite approach can effectively enhance the active sites for electrode reactions. The use of nanotechnology will make SOFCs environment friendly and sustainable through green manufacturing processes of nanotechnology. Overviews of the contributions of nanotechnology and power electronics technologies to SOFCs, the transition of SOFCs from macro- to nanotechnology, the significance of nanomaterials in SOFCs, dynamic modeling, the function of optimization techniques, and the requirement for power electronics converters in SOFCs are all provided in this piece of work. The applications of SOFCs in different sectors, prominent institutes/labs and companies involved in SOFCs’ research, future challenges, and perspectives are also highlighted.© 2023 The Authors. Energy Technology published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.fi=vertaisarvioitu|en=peerReviewed

Electrochemical Performance of Planar Solid Oxide Fuel Cell (SOFC) Stacks: From Repeat Unit to Module

The electrochemical performance of a solid oxide fuel cell (SOFC) manufactured stack module (MSM) subjected to thermal cycling sintering is generally lower than that of a unit cell tested directly. By characterizing a 10-cell stack assembled from a 5-cell testing stack and a 5-cell manufactured short stack module, the main factors that affect the electrochemical performance were determined to be the contact uniformity and depth between the interconnect and cell cathode covering the total surface. The cathode contact is improved by designing the external pressure on the stack during the manufacturing process; thus, the output power of a 30-cell MSM from a typical type of anode made from yttria-stabilized zirconia (YSZ) and lanthanum strontium manganite (LSM), Ni-YSZ/YSZ/LSM, for which the cell reached approximately 750 W power at the working temperature of 800 degrees C. Futhermore, the 30-cell MSM shows no degradation during the experiment. The electrochemical performance (herein referring to output power density and operating stability) approaches that of the corresponding unit cell being tested directly

Contribution of properties of composite cathode and cathode/electrolyte interface to cell performance in a planar solid oxide fuel cell stack

Solid oxide fuel cells (SOFCs) with distinct cathode materials usually differ in output performance. In this study, 2 mu m-thick Pt voltage probes are embedded into the cathode/electrolyte interface. The effects of the electrical properties and cathode/electrolyte interfaces of LSCF-GDC and LSM-YSZ composite cathodes on cell performance are investigated in situ for anode-supported planar SOFCs. Results show that the voltage and maximum output power density measured by the probes on both sides of the LSCF-GDC and LSM-YSZ composite cathodes are 7% and 4%, respectively, of those of the corresponding cell during instantaneous current voltage testing. The enhanced LSCF cell performance is mainly attributed to the rough GDC/LSCF-GDC interface that is responsible for the three-dimensional contact between the GDC layer and LSCF-GDC cathode particles and increases the triple-phase boundary (TPB) length. The LSM-YSZ cathode performance degradation is attributed to the variation in polarization resistance caused by cathode particle growth. However, the primary factor for the degradation of LSCF-GDC cathode performance is structural instability, such as inner cracks. (C) 2015 Elsevier B.V. All rights reserved

Properties of Supported-Anode Ni-YSZ for Planar Solid Oxide Fuel Cell Prepared by Different Reduction Processes

The properties of support-anode of Ni-YSZ reduced at isothermal and increasing temperatures were investigated. The results show that at 600 ℃, the anodes show the uniform microstructure, proper mechanical strengths of 14.92 and 56.63 MPa when the reductions at isothermal and increasing temperatures occur, respectively. The porosities of supported-anode firstly increase and then decrease with increasing the reduction temperature, and its maximum values appear at 700 and 400℃ for the reductions at isotherme l and rising temperatures, respectively. Therefore, for both the reduction processes, the optimized reduction temperature for Ni-YSZ anode-supported SOFCs is not lower than 600℃

Quantitative assessment of anode contribution to cell degradation under various polarization conditions using industrial size planar solid oxide fuel cells

Quantitative assessment of anode contribution to cell performance has been investigated under various polarization in three stack repeating units made of 10 cm x 10 cm planar anode-supported solid oxide fuel cells. The measurement is performed in-situ by inserting an ultra-thin Pt probe at the anode/electrolyte interface. The results reveal that the polarization resistance accounts for more than 90% of the total cell resistance when the cell is operated under the activation and concentration polarizations, respectively. The anode almost has no effect on cell degradation when the cell is operated under activation polarization. However, the anode has an obvious contribution to the cell degradation when the cell is operated under ohmic and concentration polarization, where the anode voltage increases by 23.36%/100 h and 512.28%/100 h, respectively. The anode operated under concentration polarization has twenty times of contribution to cell degradation than that of the ohmic polarization. However, when the cell is operated under the ohmic polarization, the main degradation comes from the ohmic resistance caused by the anode. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Probing Temperature Inside Planar SOFC Short Stack, Modules, and Stack Series

Probing temperature inside a solid oxide fuel cell (SOFC) stack lies at the heart of the development of high-performance and stable SOFC systems. In this article, we report our recent work on the direct measurements of the temperature in three types of SOFC systems: a 5-cell short stack, a 30-cell stack module, and a stack series consisting of two 30-cell stack modules. The dependence of temperature on the gas flow rate and current density was studied under a current sweep or steady-state operation. During the current sweep, the temperature inside the 5-cell stack decreased with increasing current, while it increased significantly at the bottom and top of the 30-cell stack. During a steady-state operation, the temperature of the 5-cell stack was stable while it was increased in the 30-cell stack. In the stack series, the maximum temperature gradient reached 190A degrees C when the gas was not preheated. If the gas was preheated and the temperature gradient was reduced to 23A degrees C in the stack series with the presence of a preheating gas and segmented temperature control, this resulted in a low degradation rate

Mechanism of the cathode current collector on cell performance in a solid oxide fuel cell stack

In this work, we report a new design of the contact layer to investigate the significance and mechanism for the cathodic current collection. The single cells in a stack are covered with Ag paste on the cathode side, which exhibit slightly higher power density than that of the cell partially covered with Ag paste. The Ag paste is applied as a current-collecting layer on the cathode side at the corresponding position in contact with the punctuate structure of the interconnect. The difference in power densities between the two single cells is due to the in-plane electron transfer on the cathode surface. When the structure of the interconnect is changed from a convex punctuate structure to liner strips, the cell performance is governed by both gas flow rate and in-plane electron transfer; however, the latter plays a more important role than the gas flow rate. An appropriate arrangement of current collection at the cathode side is necessary to improve current collection and thus the cell performance inside the SOFC stack. (C) 2017 Elsevier B.V. All rights reserved

Factors of cathode current-collecting layer affecting cell performance inside solid oxide fuel cell stacks

Factors of cathode current-collecting layer (CCCL) affecting cell performance are studied by investigation of solid oxide fuel cell (SOFC) stacks with various (La0.75Sr0.25)(0.95)MnO3-delta (LSM) as CCCL in-suit. A larger real contact area between cathode and interconnect appears when the LSM is coated on cathode side as CCCL through characterization of a 2-cell stack. The result reveals that the real contact area depends on the surface roughness match (SRM) between CCCL and its neighboring components (active cathode and interconnect). A 6-cell stack using CCCLs with various levels of surface roughness is assembled and characterized further. The results show a higher electrical output performance of the stack repeating unit can be obtained when the surface roughness of the CCCL matches that of its neighboring components better, i.e. the surface roughness match (SRM) is the factor of cathode current collector affecting cell performance inside stack. Accordingly, the cell performance inside SOFC stack can be regulated by designing the SRM to its neighboring components. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

Activity and Stability of (Pr1-xNdx)(2)NiO4 as Cathodes for Solid Oxide Fuel Cells

Single phase (Pr1-xNdx)(2)NiO4 cathode powders (x = 0, 0.25, 0.50, 0.75, and 1.0) were synthesized via a glycine-nitrate combustion and high temperature calcination. Anode supported cells were used to investigate the cathode property. A reproducible performance, within 9% for each cathode composition, was observed providing a wealth of data for quantitative studies. Area specific resistance analysis and i-V measurements between 650 and 850 degrees C showed a decrease in the cell performance with increasing Nd content. Impedance spectrum analysis suggests that the decline in performance results from an increase in electrode polarization. While Pr2NiO4 cells showed significant performance degradation of 6.40%/1,000 hours, the degradation rate for (Pr0.75Nd0.25)(2)NiO4 cells was reduced by an order of magnitude (0.56%/1,000 hours) with a 7% lower power output. Likewise, the cathodes with a higher Nd content showed further improvement in performance stability with a marginal degradation rate of 0.06%/1,000 hours. (C) The Author(s) 2016. Published by ECS. All rights reserved

Quantitative contribution of resistance sources of components to stack performance for planar solid oxide fuel cells

This study detects the resistance that influences the stack performance of SOFCs with composition of NiYSZ/YSZ/LSC-YSZ and investigates the variation patterns of the resistances of the stack repeating unit (SRU) during operation and their quantitative contributions to its performance at 700 degrees C, 750 degrees C and 800 degrees C. The results indicate that when the cell cathode contacts the interconnect well, the cell resistance accounts for 70.1-79.7% of that of the SRU, and the contact resistance (CR) between the cathode current-collecting layer (CCCL) and the interconnect accounts for 20.0-28.9%. The CR between the anode current-collecting layer (ACCL) and the interconnect together with the resistance of the interconnect can be neglected during instantaneous I V testing. When the stack is discharged at constant current for 600 h, cell resistance increases by 28.3%, accounting for 93.3% of the SRU degradation, the anodic CR increases by 36.4%, accounting for 6.7% of the SRU degradation, and the resistances of the cathode contact and its neighbor interconnect remain unchanged. Therefore, the increase of the cell resistance is the main reason causing the SRU degradation, and the anodic contact is also an influencing factor that cannot be neglected during stable operation. (C) 2013 Elsevier B.V. All rights reserved