Research

Open AccessArticle

Developing CeO₂-CoAl₂O₄ Semiconductor Ionic Based Heterostructure Composite Electrolyte for Low-Temperature Solid Oxide Fuel Cells (SOFCs)

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Yiwang Dong

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Muhammad Yousaf

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Muhammad Ali Kamran Yousaf Shah

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Crystals 2023, 13(6), 975; https://doi.org/10.3390/cryst13060975 - 19 Jun 2023

Viewed by 542

Abstract

Semiconductor ionic electrolytes, especially heterostructure composites, have a significant role in enhancing oxide ion conductivity and peak power density (PPD) because of their interfacial contact. In this work, the fluorite structure CeO₂ and spinel-based CoAl₂O₄ samples, as a heterostructure [...] Read more.

Semiconductor ionic electrolytes, especially heterostructure composites, have a significant role in enhancing oxide ion conductivity and peak power density (PPD) because of their interfacial contact. In this work, the fluorite structure CeO₂ and spinel-based CoAl₂O₄ samples, as a heterostructure composite electrolyte, are successfully fabricated. The p-type CoAl₂O₄ and n-type CeO₂ heterostructure (CeO₂-CoAl₂O₄) used as an electrolyte exhibits a cell performance of 758 mW/cm² under fuel cell H₂/air conditions at 550 °C, which is quite higher than the pure CoAl₂O₄ and CeO₂ fuel cell devices. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) verified the heterostructure formation including the morphological analysis of the prepared heterostructure composite. The heterostructure-based CeO₂-CoAl₂O₄ composite achieved a higher ionic conductivity of 0.13 S/cm at 550 °C temperature, which means that the constructed device successfully works as an electrolyte by suppressing electronic conductivity. Meanwhile, the obtained results demonstrate the semiconductor ionic heterostructure effect by adjusting the appropriate composition to build heterostructure of the n-type (CeO₂) and p-type (CoAl₂O₄) components and built-in electric field. So, this work exhibits that the constructed device can be effective for energy conversion and storage devices. Full article

(This article belongs to the Special Issue Frontiers in Semiconductor Heterostructures Materials)

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Open AccessArticle

Developing the Fast Ionic Transport in the Semiconductor Ionic Heterostructure Composed of La_0.8Sr_0.2Co_0.8Fe_0.2-Gd_0.1Ce_0.9O₂ for the Electrolyte Application in Ceramic Fuel Cells

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Crystals 2023, 13(4), 697; https://doi.org/10.3390/cryst13040697 - 19 Apr 2023

Viewed by 701

Abstract

The challenging research topic for developing low-temperature ceramic fuel cells (LT-CFCs) is to design electrolytes with sufficient ionic conductivity either via doping or composite semiconductors with ionic conductors. Following this challenging topic, we have developed and synthesized a novel semiconductor ionic heterostructure La [...] Read more.

The challenging research topic for developing low-temperature ceramic fuel cells (LT-CFCs) is to design electrolytes with sufficient ionic conductivity either via doping or composite semiconductors with ionic conductors. Following this challenging topic, we have developed and synthesized a novel semiconductor ionic heterostructure La_0.8Sr_0.2Co_0.8Fe_0.2O₃-Gd_0.1Ce_0.9O₂ (LSCF-GDC) with different compositions and deployed it as an electrolyte to realize the functionality of the fuel cell. The developed LSCF-GDC electrolyte with mixed conduction of ions and protons possesses high ionic conductivity with only 0.06 Ohm·cm² of ohmic area-specific resistance for the electrolyte component. The fuel cell using 3LSCF-7GDC as the electrolyte exhibits the best fuel cell performance of 1060 mW·cm⁻² and an open circuit voltage (OCV) of 1.11 V at a low operating temperature of 550 °C among individual GDC, LSCF, and different heterostructures of LSCF and GDC. The attained performance and ionic conductivity are specially accredited to constructing heterostructures and massively deficient structures at the interface of the LSCF and GDC. The advanced semiconductor ionic heterostructure of LSCF-GDC provides new insight into designing new electrolytes with high ionic conductivity for LT-CFC applications. Full article

(This article belongs to the Special Issue Frontiers in Semiconductor Heterostructures Materials)

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Open AccessArticle

Investigating the Electrochemical Properties of a Semiconductor Heterostructure Composite Based on WO₃-CaFe₂O₄ Particles Planted on Porous Ni-Foam for Fuel Cell Applications

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Crystals 2023, 13(3), 444; https://doi.org/10.3390/cryst13030444 - 04 Mar 2023

Cited by 1 | Viewed by 1006

Abstract

There is tremendous potential for both small- and large-scale applications of low-temperature operational ceramic fuel cells (LT-CFCs), which operate between 350 °C and 550 °C. Unfortunately, the low operating temperature of CFCs was hampered by inadequate oxygen reduction electrocatalysts. In this work, the [...] Read more.

There is tremendous potential for both small- and large-scale applications of low-temperature operational ceramic fuel cells (LT-CFCs), which operate between 350 °C and 550 °C. Unfortunately, the low operating temperature of CFCs was hampered by inadequate oxygen reduction electrocatalysts. In this work, the electrochemical characteristics of a semiconductor heterostructure composite based on WO₃-CaFe₂O₄ deposited over porous Ni-foam are investigated. At low working temperatures of 450–500 °C, the developed WO₃-CaFe₂O₄ pasted on porous Ni–foam heterostructure composite cathode exhibits very low area-specific resistance (0.78 Ω cm²) and high oxygen reduction reaction (ORR) activity. For button-sized SOFCs with H₂ and atmospheric air fuels, we have demonstrated high-power densities of 508 mW cm⁻² running at 550 °C, and even potential operation at 450 °C, using WO₃-CaFe₂O₄ seeded on porous Ni-foam cathode. Moreover, WO₃-CaFe₂O₄ composite heterostructure with Ni foam paste exhibits very low activation energy compared to both WO₃ and CaFe₂O₄ alone, which supports ORR activity. To comprehend the enhanced ORR electrocatalytic activity of WO₃-CaFe₂O₄ pasted on porous Ni-foam heterostructure composite, several spectroscopic tests including X-ray diffraction (XRD), photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) were used. The findings may also aid in the creation of useful cobalt-free electrocatalysts for LT-SOFCs. Full article

(This article belongs to the Special Issue Frontiers in Semiconductor Heterostructures Materials)

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Open AccessArticle

Supercilious Enhancement in Oxygen-Reduction Catalytic Functionalities of Cubic Perovskite Structured LaFeO₃ by Co-Doping of Gd and Ce for LT-SOFCs

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Crystals 2023, 13(2), 242; https://doi.org/10.3390/cryst13020242 - 31 Jan 2023

Cited by 1 | Viewed by 920

Abstract

Low-temperature solid fuel cells (LT-SOFCs) hold remarkable promise for the cooperative corporation of small- and large-scale applications. However, the meager oxygen-reduction retort of cathode materials mires the low operating temperature conditions of SOFCs. Herein, we have developed a perovskite structured LaFeO₃ by [...] Read more.

Low-temperature solid fuel cells (LT-SOFCs) hold remarkable promise for the cooperative corporation of small- and large-scale applications. However, the meager oxygen-reduction retort of cathode materials mires the low operating temperature conditions of SOFCs. Herein, we have developed a perovskite structured LaFeO₃ by the co-doping of Gd and Ce ions, and their electrochemical properties have been studied. The developed LaFe_0.8Gd_0.1Ce_0.1O_3-δ cathode exhibits very small-area-specific-resistance and good oxygen-reduction reaction (ORR) activity at low operating temperatures of 450–500 °C. We have demonstrated a high-power density of 0.419 W-cm⁻² with a LaFe_0.8Gd_0.1Ce_0.1O_3-δ cathode operating at 550 °C with H₂ and atmospheric air as fuels. Moreover, LaFe_0.8Gd_0.1Ce_0.1O_3-δ exhibits high activation energy as compared to individual LaFeO_3, which helps to promote ORR activity. Various spectroscopic measurements such as X-ray diffraction, SEM, EIS, UV-visible, TGA, Ramana, and photoelectron spectroscopy were employed to understand the improved ORR electrocatalytic activity of Gd and Ce co-doped LaFeO₃ cathode. The results can further help to develop functional cobalt-free electro-catalysts for LT-SOFCs. Full article

(This article belongs to the Special Issue Frontiers in Semiconductor Heterostructures Materials)

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Open AccessArticle

Designing Composite BaCe_0.4Zr_0.4Y_0.1Yb_0.1O_3-δ-Sm_0.2Ce_0.8O_2-δ Heterostructure Electrolyte for Low-Temperature Ceramic Fuel Cell (LT-CFCs)

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Crystals 2023, 13(1), 41; https://doi.org/10.3390/cryst13010041 - 26 Dec 2022

Viewed by 1442

Abstract

In recent years, tuning perovskite and fluorite-based materials and modifying them to ionic conductors has been an interesting but challenging topic for advanced low-temperature ceramic fuel cells (LT-CFCs). In this regard, we prepared a new composite heterostructure, BaCe_0.4Zr_0.4Y_0.1 [...] Read more.

In recent years, tuning perovskite and fluorite-based materials and modifying them to ionic conductors has been an interesting but challenging topic for advanced low-temperature ceramic fuel cells (LT-CFCs). In this regard, we prepared a new composite heterostructure, BaCe_0.4Zr_0.4Y_0.1Yb_0.1O3-Sm_0.2Ce_0.8O₂ (BCZYYb-SDC), and evaluated it as an electrolyte to realize the fuel cell reaction. The developed electrolyte could be a hybrid ionic conductor, possess a very small ohmic area-specific resistance, and exhibit excellent fuel cell performance of over 1.0 W/cm² along with higher OCV of more than 1.1 V at a low operating temperature of 550 °C. The attained performance and ionic conductivity are specially accredited to constructing the heterostructure of BCZYYb-SDC. Moreover, various spectroscopy and microscopic analysis methods have been used to investigate the ions’ transportation, while on the other hand suppressing the electronic conduction. The developed composite heterostructure proposes and suggests new insight to design new electrolytes for LT-CFCs. Full article

(This article belongs to the Special Issue Frontiers in Semiconductor Heterostructures Materials)

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Open AccessArticle

Oxygen Reduction Response of La and Ce Co-Doped SrCoO_3−δ Perovskite Oxide Grown on Porous Ni-Foam Substrate

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Crystals 2022, 12(11), 1650; https://doi.org/10.3390/cryst12111650 - 16 Nov 2022

Cited by 1 | Viewed by 869

Abstract

Lately, ceramic fuel cells (CFCs) have held exceptional promise for joint small- and large-scale applications. However, the low-oxygen reduction response of cathode materials has hindered the low operating temperature of CFCs. Herein, we have developed a semiconductor based on La and Ce co-doped [...] Read more.

Lately, ceramic fuel cells (CFCs) have held exceptional promise for joint small- and large-scale applications. However, the low-oxygen reduction response of cathode materials has hindered the low operating temperature of CFCs. Herein, we have developed a semiconductor based on La and Ce co-doped SrCoO₃ and embedded them in porous Ni-foam to study their electrochemical properties. The porous Ni-foam-pasted La_0.2Sr_0.8Co_0.8Ce_0.2O_3‒δ cathode displays small-area-specific resistance and excellent ORR (oxygen reduction reaction) activity at low operating temperatures (LT) of 450–500 °C. The proposed device has delivered an impressive fuel cell performance of 440 mW-cm⁻², using La_0.2Sr_0.8Co_0.8Ce_0.2O_3−δ embedded on porous Ni-foam substrate cathode operation at 550 °C with H₂ fuel and atmospheric air. It even can function well at a lower temperature of 450 °C. Moreover, La_0.2Sr_0.8Co_0.8Ce_0.2O_3−δ embedded on porous Ni-foam shows very good activation energy compared to individual SrCoO₃ and La_0.1Sr_0.9Co_0.9Ce_0.1O_3−δ embedded on porous Ni-foam, which help to promote ORR activity. Different characterization has been deployed, likewise: X-ray diffraction, photoelectron-spectroscopy, and electrochemical impedance spectroscopy for a better understanding of improved ORR electrocatalytic activity of prepared La_0.2Sr_0.8Co_0.8Ce_0.2O_3−δ embedded on porous Ni-foam substrate. These results can further help to develop functional cobalt-free electrocatalysts for LT-SOFCs. Full article

(This article belongs to the Special Issue Frontiers in Semiconductor Heterostructures Materials)

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Open AccessArticle

Introducing Fuel Cell Application Using Sodium Vacancies in Hexagonal Wurtzite Structured ZnO Nanorods for Developing Proton–Ion Conductivity

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Crystals 2022, 12(11), 1594; https://doi.org/10.3390/cryst12111594 - 09 Nov 2022

Viewed by 867

Abstract

Zinc oxide, a direct band gap semiconductor of ≥3.30 eV, is prevalent in potential requests for energy devices. The early-stage demonstration of ZnO provides a new method of developing high ionic conductivity in multifunctional semiconductors for electrolyte applications in ceramic fuel cells (CFCs). [...] Read more.

Zinc oxide, a direct band gap semiconductor of ≥3.30 eV, is prevalent in potential requests for energy devices. The early-stage demonstration of ZnO provides a new method of developing high ionic conductivity in multifunctional semiconductors for electrolyte applications in ceramic fuel cells (CFCs). In the present work, we successfully synthesized Na-doped ZnO nanorods by a hydrothermal method and employed them as an electrolyte in CFCs. The synthesized Na-doped-ZnO nanorods showed an effective ionic conductivity of 8.75 × 10⁻² S cm⁻¹ along with an excellent power density of 609 mWcm⁻² ± 5% when the fuel cell was operating at 550 °C. The enhanced ionic conductivity could be due to Na+ doping into Zn²⁺ and the high ionic radius of Na ions producing bulk oxygen vacancies in the ZnO structure to conduct oxygen ions or protons. Furthermore, we used experimental analysis, such as X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), ultraviolet–visible (UV–visible), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS), to evaluate the change in structural properties and mechanism of ionic transport in ZnO nanorods with sodium doping. The presented work provides insight into a novel approach of developing the high ionic conductivity of electrolytes in a low-cost ZnO semiconductor material. Full article

(This article belongs to the Special Issue Frontiers in Semiconductor Heterostructures Materials)

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Open AccessArticle

Proton-Ion Conductivity in Hexagonal Wurtzite-Nanostructured ZnO Particles When Exposed to a Reducing Atmosphere

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Muhammad Sultan Irshad

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Rong Yan

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Senlin Yan

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Yuzheng Lu

Crystals 2022, 12(11), 1519; https://doi.org/10.3390/cryst12111519 - 26 Oct 2022

Cited by 1 | Viewed by 912

Abstract

Zinc oxide (ZnO), a direct wide band gap semiconductor (≥3.30 eV), has widespread potential for applications in energy devices and related industries. The initial physical demonstration of ZnO in ceramic fuel cells (CFCs) gave a new view of developing high ionic conductivity for [...] Read more.

Zinc oxide (ZnO), a direct wide band gap semiconductor (≥3.30 eV), has widespread potential for applications in energy devices and related industries. The initial physical demonstration of ZnO in ceramic fuel cells (CFCs) gave a new view of developing high ionic conductivity for multifunctional semiconductor technology. However, in the present work, we successfully synthesized highly textured nanoparticles of ZnO using a hydrothermal method followed by sintering in a reducing atmosphere. The resultant ZnO materials as electrolytes showed efficient ionic conductivity (5.28 × 10⁻² S cm⁻¹) and an excellent power density of 520 mW cm⁻² ± 5% at 550 °C for low-temperature ceramic fuel cells (LT-CFCs). The achievement of enhanced ionic conductivity without any external ions or cation doping in the CFC was anticipated, since there was a rare possibility of vacancies in the bulk ZnO structure to conduct oxygen ions or protons. Therefore, we found that laterally the surfaces of the ZnO nanoparticles could be textured to become oxygen-deficient when sintered in an H₂ atmosphere, which suggests a special mechanism for effective ionic transport. Furthermore, experimental analyses such as SEM, XPS, UV–visible, and EIS methods were performed to analyze the changes in the structural properties and mechanism of ionic transport in ZnO nanoparticles. The presented work provides insights into a novel approach for developing high ionic conductivity in electrolytes in low-cost semiconductor oxides such as ZnO for energy storage and conversion devices. Full article

(This article belongs to the Special Issue Frontiers in Semiconductor Heterostructures Materials)

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