Nanocrystalline Surface Layer of WO<sub>3</sub> for Enhanced Proton Transport during Fuel Cell Operation
High ionic conductivity in low-cost semiconductor oxides is essential to develop electrochemical energy devices for practical applications. These materials exhibit fast protonic or oxygen-ion transport in oxide materials by structural doping, but their application to solid oxide fuel cells (SOFCs) h...
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MDPI AG
2021-12-01
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| Series: | Crystals |
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| author | Xiang Song Weiqing Guo Yuhong Guo Naveed Mushtaq M. A. K. Yousaf Shah Muhammad Sultan Irshad Peter D. Lund Muhammad Imran Asghar |
| author_facet | Xiang Song Weiqing Guo Yuhong Guo Naveed Mushtaq M. A. K. Yousaf Shah Muhammad Sultan Irshad Peter D. Lund Muhammad Imran Asghar |
| author_sort | Xiang Song |
| collection | DOAJ |
| description | High ionic conductivity in low-cost semiconductor oxides is essential to develop electrochemical energy devices for practical applications. These materials exhibit fast protonic or oxygen-ion transport in oxide materials by structural doping, but their application to solid oxide fuel cells (SOFCs) has remained a significant challenge. In this work, we have successfully synthesized nanostructured monoclinic WO<sub>3</sub> through three steps: co-precipitation, hydrothermal, and dry freezing methods. The resulting WO<sub>3</sub> exhibited good ionic conductivity of 6.12 × 10<sup>−2</sup> S cm<sup>−1</sup> and reached an excellent power density of 418 mW cm<sup>−2</sup> at 550 °C using as an electrolyte in SOFC. To achieve such a high ionic conductivity and fuel cell performance without any doping contents was surprising, as there should not be any possibility of oxygen vacancies through the bulk structure for the ionic transport. Therefore, laterally we found that the surface layer of WO<sub>3</sub> is reduced to oxygen-deficient when exposed to a reducing atmosphere and form WO<sub>3−δ</sub>/WO<sub>3</sub> heterostructure, which reveals a unique ionic transport mechanism. Different microscopic and spectroscopic methods such as HR-TEM, SEM, EIS, Raman, UV-visible, XPS, and ESR spectroscopy were applied to investigate the structural, morphological, and electrochemical properties of WO<sub>3</sub> electrolyte. The structural stability of the WO<sub>3</sub> is explained by less dispersion between the valence and conduction bands of WO<sub>3−δ</sub>/WO<sub>3</sub>, which in turn could prevent current leakage in the fuel cell that is essential to reach high performance. This work provides some new insights for designing high-ion conducting electrolyte materials for energy storage and conversion devices. |
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| spelling | doaj.art-0fefce3a66524c918df7f6ca03759bbc2023-11-23T07:49:52ZengMDPI AGCrystals2073-43522021-12-011112159510.3390/cryst11121595Nanocrystalline Surface Layer of WO<sub>3</sub> for Enhanced Proton Transport during Fuel Cell OperationXiang Song0Weiqing Guo1Yuhong Guo2Naveed Mushtaq3M. A. K. Yousaf Shah4Muhammad Sultan Irshad5Peter D. Lund6Muhammad Imran Asghar7School of Electronic Engineering, Nanjing Xiaozhuang University, Nanjing 211171, ChinaZhijiang College, Zhejiang University of Technology, Shaoxing 312030, ChinaHuadong Engineering Corporation Limited, Hangzhou 311122, ChinaJiangsu Provincial Key Laboratory of Solar Energy Science and Technology, Energy Storage Joint Research Center, School of Energy and Environment, Southeast University, Nanjing 210096, ChinaJiangsu Provincial Key Laboratory of Solar Energy Science and Technology, Energy Storage Joint Research Center, School of Energy and Environment, Southeast University, Nanjing 210096, ChinaSchool of Materials Science and Engineering, Hubei University, Wuhan 430062, ChinaNew Energy Technologies Group, Department of Applied Physics, Aalto University School of Science, Aalto, FI-00076 Espoo, FinlandNew Energy Technologies Group, Department of Applied Physics, Aalto University School of Science, Aalto, FI-00076 Espoo, FinlandHigh ionic conductivity in low-cost semiconductor oxides is essential to develop electrochemical energy devices for practical applications. These materials exhibit fast protonic or oxygen-ion transport in oxide materials by structural doping, but their application to solid oxide fuel cells (SOFCs) has remained a significant challenge. In this work, we have successfully synthesized nanostructured monoclinic WO<sub>3</sub> through three steps: co-precipitation, hydrothermal, and dry freezing methods. The resulting WO<sub>3</sub> exhibited good ionic conductivity of 6.12 × 10<sup>−2</sup> S cm<sup>−1</sup> and reached an excellent power density of 418 mW cm<sup>−2</sup> at 550 °C using as an electrolyte in SOFC. To achieve such a high ionic conductivity and fuel cell performance without any doping contents was surprising, as there should not be any possibility of oxygen vacancies through the bulk structure for the ionic transport. Therefore, laterally we found that the surface layer of WO<sub>3</sub> is reduced to oxygen-deficient when exposed to a reducing atmosphere and form WO<sub>3−δ</sub>/WO<sub>3</sub> heterostructure, which reveals a unique ionic transport mechanism. Different microscopic and spectroscopic methods such as HR-TEM, SEM, EIS, Raman, UV-visible, XPS, and ESR spectroscopy were applied to investigate the structural, morphological, and electrochemical properties of WO<sub>3</sub> electrolyte. The structural stability of the WO<sub>3</sub> is explained by less dispersion between the valence and conduction bands of WO<sub>3−δ</sub>/WO<sub>3</sub>, which in turn could prevent current leakage in the fuel cell that is essential to reach high performance. This work provides some new insights for designing high-ion conducting electrolyte materials for energy storage and conversion devices.https://www.mdpi.com/2073-4352/11/12/1595fuel cellsolid oxide fuel cellmonoclinic WO<sub>3</sub> electrolytedry freezing methodproton conductionspectroscopic analysis |
| spellingShingle | Xiang Song Weiqing Guo Yuhong Guo Naveed Mushtaq M. A. K. Yousaf Shah Muhammad Sultan Irshad Peter D. Lund Muhammad Imran Asghar Nanocrystalline Surface Layer of WO<sub>3</sub> for Enhanced Proton Transport during Fuel Cell Operation Crystals fuel cell solid oxide fuel cell monoclinic WO<sub>3</sub> electrolyte dry freezing method proton conduction spectroscopic analysis |
| title | Nanocrystalline Surface Layer of WO<sub>3</sub> for Enhanced Proton Transport during Fuel Cell Operation |
| title_full | Nanocrystalline Surface Layer of WO<sub>3</sub> for Enhanced Proton Transport during Fuel Cell Operation |
| title_fullStr | Nanocrystalline Surface Layer of WO<sub>3</sub> for Enhanced Proton Transport during Fuel Cell Operation |
| title_full_unstemmed | Nanocrystalline Surface Layer of WO<sub>3</sub> for Enhanced Proton Transport during Fuel Cell Operation |
| title_short | Nanocrystalline Surface Layer of WO<sub>3</sub> for Enhanced Proton Transport during Fuel Cell Operation |
| title_sort | nanocrystalline surface layer of wo sub 3 sub for enhanced proton transport during fuel cell operation |
| topic | fuel cell solid oxide fuel cell monoclinic WO<sub>3</sub> electrolyte dry freezing method proton conduction spectroscopic analysis |
| url | https://www.mdpi.com/2073-4352/11/12/1595 |
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