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14 pages, 4603 KiB

Open AccessArticle

Self-Assembled Triple (H⁺/O²⁻/e⁻) Conducting Nanocomposite of Ba-Co-Ce-Y-O into an Electrolyte for Semiconductor Ionic Fuel Cells

by Dan Xu, An Yan, Shifeng Xu, Yongjun Zhou, Shu Yang, Rongyu Zhang, Xu Yang and Yuzheng Lu

Nanomaterials 2021, 11(9), 2365; https://doi.org/10.3390/nano11092365 - 11 Sep 2021

Cited by 2 | Viewed by 1956

Abstract

Triple (H⁺/O²⁻/e⁻) conducting oxides (TCOs) have been extensively investigated as the most promising cathode materials for solid oxide fuel cells (SOFCs) because of their excellent catalytic activity for oxygen reduction reaction (ORR) and fast proton transport. However, [...] Read more.

Triple (H⁺/O²⁻/e⁻) conducting oxides (TCOs) have been extensively investigated as the most promising cathode materials for solid oxide fuel cells (SOFCs) because of their excellent catalytic activity for oxygen reduction reaction (ORR) and fast proton transport. However, here we report a stable twin-perovskite nanocomposite Ba-Co-Ce-Y-O (BCCY) with triple conducting properties as a conducting accelerator in semiconductor ionic fuel cells (SIFCs) electrolytes. Self-assembled BCCY nanocomposite is prepared through a complexing sol–gel process. The composite consists of a cubic perovskite (Pm-3m) phase of BaCo_0.9Ce_0.01Y_0.09O_3-δ and a rhombohedral perovskite (R-3c) phase of BaCe_0.78Y_0.22O_3-δ. A new semiconducting–ionic conducting composite electrolyte is prepared for SIFCs by the combination of BCCY and CeO₂ (BCCY-CeO₂). The fuel cell with the prepared electrolyte (400 μm in thickness) can deliver a remarkable peak power density of 1140 mW·cm⁻² with a high open circuit voltage (OCV) of 1.15 V at 550 °C. The interface band energy alignment is employed to explain the suppression of electronic conduction in the electrolyte. The hybrid H⁺/O²⁻ ions transport along the surfaces or grain boundaries is identified as a new way of ion conduction. The comprehensive analysis of the electrochemical properties indicates that BCCY can be applied in electrolyte, and has shown tremendous potential to improve ionic conductivity and electrochemical performance. Full article

(This article belongs to the Special Issue Advanced Fuel Cells and Solid Batteries)

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17 pages, 5524 KiB

Open AccessArticle

Remarkable Ionic Conductivity in a LZO-SDC Composite for Low-Temperature Solid Oxide Fuel Cells

by Zhengwen Tu, Yuanyuan Tian, Mingyang Liu, Bin Jin, Muhammad Akbar, Naveed Mushtaq, Xunying Wang, Wenjing Dong, Baoyuan Wang and Chen Xia

Nanomaterials 2021, 11(9), 2277; https://doi.org/10.3390/nano11092277 - 1 Sep 2021

Cited by 17 | Viewed by 2626

Abstract

Recently, appreciable ionic conduction has been frequently observed in multifunctional semiconductors, pointing out an unconventional way to develop electrolytes for solid oxide fuel cells (SOFCs). Among them, ZnO and Li-doped ZnO (LZO) have shown great potential. In this study, to further improve the [...] Read more.

Recently, appreciable ionic conduction has been frequently observed in multifunctional semiconductors, pointing out an unconventional way to develop electrolytes for solid oxide fuel cells (SOFCs). Among them, ZnO and Li-doped ZnO (LZO) have shown great potential. In this study, to further improve the electrolyte capability of LZO, a typical ionic conductor Sm_0.2Ce_0.8O_1.9 (SDC) is introduced to form semiconductor-ionic composites with LZO. The designed LZO-SDC composites with various mass ratios are successfully demonstrated in SOFCs at low operating temperatures, exhibiting a peak power density of 713 mW cm⁻² and high open circuit voltages (OCVs) of 1.04 V at 550 °C by the best-performing sample 5LZO-5SDC, which is superior to that of simplex LZO electrolyte SOFC. Our electrochemical and electrical analysis reveals that the composite samples have attained enhanced ionic conduction as compared to pure LZO and SDC, reaching a remarkable ionic conductivity of 0.16 S cm⁻¹ at 550 °C, and shows hybrid H⁺/O²⁻ conducting capability with predominant H⁺ conduction. Further investigation in terms of interface inspection manifests that oxygen vacancies are enriched at the hetero-interface between LZO and SDC, which gives rise to the high ionic conductivity of 5LZO-5SDC. Our study thus suggests the tremendous potentials of semiconductor ionic materials and indicates an effective way to develop fast ionic transport in electrolytes for low-temperature SOFCs. Full article

(This article belongs to the Special Issue Advanced Fuel Cells and Solid Batteries)

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12 pages, 4066 KiB

Open AccessArticle

High Performance Low-Temperature Solid Oxide Fuel Cells Based on Nanostructured Ceria-Based Electrolyte

by Jiamei Liu, Chengjun Zhu, Decai Zhu, Xin Jia, Yingbo Zhang, Jie Yu, Xinfang Li and Min Yang

Nanomaterials 2021, 11(9), 2231; https://doi.org/10.3390/nano11092231 - 29 Aug 2021

Cited by 22 | Viewed by 2760

Abstract

Ceria based electrolyte materials have shown potential application in low temperature solid oxide fuel cells (LT-SOFCs). In this paper, Sm³⁺ and Nd³⁺ co-doped CeO₂ (SNDC) and pure CeO₂ are synthesized via glycine-nitrate process (GNP) and the electro-chemical properties of [...] Read more.

Ceria based electrolyte materials have shown potential application in low temperature solid oxide fuel cells (LT-SOFCs). In this paper, Sm³⁺ and Nd³⁺ co-doped CeO₂ (SNDC) and pure CeO₂ are synthesized via glycine-nitrate process (GNP) and the electro-chemical properties of the nanocrystalline structure electrolyte are investigated using complementary techniques. The result shows that Sm³⁺ and Nd³⁺ have been successfully doped into CeO₂ lattice, and has the same cubic fluorite structure before, and after, doping. Sm³⁺ and Nd³⁺ co-doped causes the lattice distortion of CeO₂ and generates more oxygen vacancies, which results in high ionic conductivity. The fuel cells with the nanocrystalline structure SNDC and CeO₂ electrolytes have exhibited excellent electrochemical performances. At 450, 500 and 550 °C, the fuel cell for SNDC can achieve an extraordinary peak power densities of 406.25, 634.38, and 1070.31 mW·cm⁻², which is, on average, about 1.26 times higher than those (309.38, 562.50 and 804.69 mW·cm⁻²) for pure CeO₂ electrolyte. The outstanding performance of SNDC cell is closely related to the high ionic conductivity of SNDC electrolyte. Moreover, the encouraging findings suggest that the SNDC can be as potential candidate in LT-SOFCs application. Full article

(This article belongs to the Special Issue Advanced Fuel Cells and Solid Batteries)

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14 pages, 4201 KiB

Open AccessArticle

Systematic Analysis on the Effect of Sintering Temperature for Optimized Performance of Li_0.15Ni_0.45Zn_0.4O₂-Gd_0.2Ce_0.8O₂-Li₂CO₃-Na₂CO₃-K₂CO₃ Based 3D Printed Single-Layer Ceramic Fuel Cell

by Muhammad Imran Asghar, Pyry Mäkinen, Sini Virtanen, Anna Maitre, Maryam Borghei and Peter D. Lund

Nanomaterials 2021, 11(9), 2180; https://doi.org/10.3390/nano11092180 - 25 Aug 2021

Cited by 2 | Viewed by 2481

Abstract

Single-layer ceramic fuel cells consisting of Li_0.15Ni_0.45Zn_0.4O₂, Gd_0.2Ce_0.8O₂ and a eutectic mixture of Li₂CO₃, Na₂CO₃ and K₂CO₃, were fabricated [...] Read more.

Single-layer ceramic fuel cells consisting of Li_0.15Ni_0.45Zn_0.4O₂, Gd_0.2Ce_0.8O₂ and a eutectic mixture of Li₂CO₃, Na₂CO₃ and K₂CO₃, were fabricated through extrusion-based 3D printing. The sintering temperature of the printed cells was varied from 700 °C to 1000 °C to identify the optimal thermal treatment to maximize the cell performance. It was found that the 3D printed single-layer cell sintered at 900 °C produced the highest power density (230 mW/cm²) at 550 °C, which is quite close to the performance (240 mW/cm²) of the single-layer cell fabricated through a conventional pressing method. The best printed cell still had high ohmic (0.46 Ω·cm²) and polarization losses (0.32 Ω·cm²) based on EIS measurements conducted in an open-circuit condition. The XRD spectra showed the characteristic peaks of the crystalline structures in the composite material. HR-TEM, SEM and EDS measurements revealed the morphological information of the composite materials and the distribution of the elements, respectively. The BET surface area of the single-layer cells was found to decrease from 2.93 m²/g to 0.18 m²/g as the sintering temperature increased from 700 °C to 1000 °C. The printed cell sintered at 900 °C had a BET surface area of 0.34 m²/g. The fabrication of single-layer ceramic cells through up-scalable 3D technology could facilitate the scaling up and commercialization of this promising fuel cell technology. Full article

(This article belongs to the Special Issue Advanced Fuel Cells and Solid Batteries)

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15 pages, 9252 KiB

Open AccessArticle

An Interface Heterostructure of NiO and CeO₂ for Using Electrolytes of Low-Temperature Solid Oxide Fuel Cells

by Junjiao Li, Jun Xie, Dongchen Li, Lei Yu, Chaowei Xu, Senlin Yan and Yuzheng Lu

Nanomaterials 2021, 11(8), 2004; https://doi.org/10.3390/nano11082004 - 5 Aug 2021

Cited by 12 | Viewed by 2017

Abstract

Interface engineering can be used to tune the properties of heterostructure materials at an atomic level, yielding exceptional final physical properties. In this work, we synthesized a heterostructure of a p-type semiconductor (NiO) and an n-type semiconductor (CeO₂) for solid oxide [...] Read more.

Interface engineering can be used to tune the properties of heterostructure materials at an atomic level, yielding exceptional final physical properties. In this work, we synthesized a heterostructure of a p-type semiconductor (NiO) and an n-type semiconductor (CeO₂) for solid oxide fuel cell electrolytes. The CeO₂-NiO heterostructure exhibited high ionic conductivity of 0.2 S cm⁻¹ at 530 °C, which was further improved to 0.29 S cm⁻¹ by the introduction of Na⁺ ions. When it was applied in the fuel cell, an excellent power density of 571 mW cm⁻¹ was obtained, indicating that the CeO₂-NiO heterostructure can provide favorable electrolyte functionality. The prepared CeO₂-NiO heterostructures possessed both proton and oxygen ionic conductivities, with oxygen ionic conductivity dominating the fuel cell reaction. Further investigations in terms of electrical conductivity and electrode polarization, a proton and oxygen ionic co-conducting mechanism, and a mechanism for blocking electron transport showed that the reconstruction of the energy band at the interfaces was responsible for the enhanced ionic conductivity and cell power output. This work presents a new methodology and scientific understanding of semiconductor-based heterostructures for advanced ceramic fuel cells. Full article

(This article belongs to the Special Issue Advanced Fuel Cells and Solid Batteries)

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10 pages, 1988 KiB

Open AccessArticle

Theoretical Investigation of Proton Diffusion in Dion–Jacobson Layered Perovskite RbBiNb₂O₇

by Jing Shi, Chang Han, Haibo Niu, Youzhang Zhu and Sining Yun

Nanomaterials 2021, 11(8), 1953; https://doi.org/10.3390/nano11081953 - 29 Jul 2021

Cited by 5 | Viewed by 4420

Abstract

Perovskite materials are considered to be promising electrolyte membrane candidates for electrochemical applications owing to their excellent proton- or oxide-ion-conducting properties. RbBiNb₂O₇ is a double-layered Dion–Jacobson perovskite oxide, with Pmc2₁ symmetry. In this study, the electronic structure and proton-diffusion [...] Read more.

Perovskite materials are considered to be promising electrolyte membrane candidates for electrochemical applications owing to their excellent proton- or oxide-ion-conducting properties. RbBiNb₂O₇ is a double-layered Dion–Jacobson perovskite oxide, with Pmc2₁ symmetry. In this study, the electronic structure and proton-diffusion properties of bulk RbBiNb₂O₇ were systematically investigated using first-principles calculations. The unique layered crystal structure of RbBiNb₂O₇ plays a crucial role in proton storage and proton conductivity. Different proton-diffusion steps in RbBiNb₂O₇ were considered, and the activation energies of the relevant diffusion steps were evaluated using the climbing image-nudged elastic band (CI-NEB) technique. The proton diffusion in RbBiNb₂O₇ presents a two-dimensional layered characteristic in the a-b plane, owing to its layered crystalline nature. According to the transition state calculations, our results show that the bulk RbBiNb₂O₇ exhibits good proton-transport behavior in the a-b plane, which is better than many perovskite oxides, such as CaTiO₃, CaZrO₃, and SrZrO₃. The proton diffusion in the Rb–O and Nb–O layers is isolated by a higher energy barrier of 0.86 eV. The strong octahedral tilting in RbBiNb₂O₇ would promote proton transport. Our study reveals the microscopic mechanisms of proton conductivity in Dion–Jacobson structured RbBiNb₂O₇, and provides theoretical evidence for its potential application as an electrolyte in solid oxide fuel cells (SOFCs). Full article

(This article belongs to the Special Issue Advanced Fuel Cells and Solid Batteries)

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8 pages, 2053 KiB

Open AccessArticle

Standardized Procedures Important for Improving Low-Temperature Ceramic Fuel Cell Technology: From Transient to Steady State Assessment

by Fan Yang, Yifei Zhang, Jingjing Liu, Muhammad Yousaf and Xinlei Yang

Nanomaterials 2021, 11(8), 1923; https://doi.org/10.3390/nano11081923 - 26 Jul 2021

Cited by 1 | Viewed by 2236

Abstract

As the stress–strain curve of standardized metal samples provides the basic details about mechanical properties of structural materials, the polarization curve or current–voltage characteristics of fuel cells are vitally important to explore the scientific mechanism of various solid oxide cells aiming at low [...] Read more.

As the stress–strain curve of standardized metal samples provides the basic details about mechanical properties of structural materials, the polarization curve or current–voltage characteristics of fuel cells are vitally important to explore the scientific mechanism of various solid oxide cells aiming at low operational temperatures (below 600 °C), ranging from protonic conductor ceramic cells (PCFC) to emerging Semiconductor ionic fuel cell (SIFC)/Semiconductor membrane fuel cells (SMFC). Thus far, worldwide efforts to achieve higher nominal peak power density (PPD) at a low operational temperature of over 0.1 s/cm ionic conductivity of electrolyte and super catalyst electrode is the key challenge for SIFCs. Thus, we illustrate an alternative approach to the present PPD concept and current–voltage characteristic. Case studies reveal that the holy grail of 1 W/cm² from journal publications is expected to be reconsidered and normalized, since partial cells may still remain in a transient state (TS) to some extent, which means that they are unable to fulfill the prerequisite of a steady state (SS) characteristic of polarization curve measurement. Depending on the testing parameters, the reported PPD value can arbitrarily exist between higher transient power density (TPD) and lower stable power density (SPD). Herein, a standardized procedure has been proposed by modifying a quasi-steady state (QSS) characterization based on stabilized cell and time-prolonged measurements of common I–V plots. The present study indicates, when compared with steady state value, that QSS power density itself still provides a better approximation for the real performance of fuel cells, and concurrently recalls a novel paradigm transformation from a transient to steady state perspective in the oxide solid fuel cell community. Full article

(This article belongs to the Special Issue Advanced Fuel Cells and Solid Batteries)

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10 pages, 2694 KiB

Open AccessArticle

Layered LiCoO_2–LiFeO₂ Heterostructure Composite for Semiconductor-Based Fuel Cells

by Yanyan Liu, Chen Xia, Baoyuan Wang and Yongfu Tang

Nanomaterials 2021, 11(5), 1224; https://doi.org/10.3390/nano11051224 - 6 May 2021

Cited by 8 | Viewed by 2421

Abstract

Enabling fast ionic transport at a low-temperature range (400–600 °C) is of great importance to promoting the development of solid oxide fuel cells (SOFCs). In this study, a layer-structured LiCoO₂–LiFeO₂ heterostructure composite is explored for the low-temperature (LT) SOFCs. Fuel [...] Read more.

Enabling fast ionic transport at a low-temperature range (400–600 °C) is of great importance to promoting the development of solid oxide fuel cells (SOFCs). In this study, a layer-structured LiCoO₂–LiFeO₂ heterostructure composite is explored for the low-temperature (LT) SOFCs. Fuel cell devices with different configurations are fabricated to investigate the multifunction property of LiCoO₂–LiFeO₂ heterostructure composites. The LiCoO₂–LiFeO₂ composite is employed as a cathode in conventional SOFCs and as a semiconductor membrane layer in semiconductor-based fuel cells (SBFCs). Enhanced ionic conductivity is realized by a composite of LiCoO₂–LiFeO₂ and Sm³⁺ doped ceria (SDC) electrolyte in SBFC. All these designed fuel cell devices display high open-circuit voltages (OCVs), along with promising cell performance. An improved power density of 714 mW cm⁻² is achieved from the new SBFC device, compared to the conventional fuel cell configuration with LiCoO₂–LiFeO₂ as the cathode (162 mW cm⁻² at 550 °C). These findings reveal promising multifunctional layered oxides for developing high-performance LT–SOFCs. Full article

(This article belongs to the Special Issue Advanced Fuel Cells and Solid Batteries)

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Review

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16 pages, 5367 KiB

Open AccessReview

Recent Progress in Semiconductor-Ionic Conductor Nanomaterial as a Membrane for Low-Temperature Solid Oxide Fuel Cells

by Yuzheng Lu, Youquan Mi, Junjiao Li, Fenghua Qi, Senlin Yan and Wenjing Dong

Nanomaterials 2021, 11(9), 2290; https://doi.org/10.3390/nano11092290 - 3 Sep 2021

Cited by 24 | Viewed by 4924

Abstract

Reducing the operating temperature of Solid Oxide Fuel Cells (SOFCs) to 300–600 °C is a great challenge for the development of SOFC. Among the extensive research and development (R&D) efforts that have been done on lowering the operating temperature of SOFCs, nanomaterials have [...] Read more.

Reducing the operating temperature of Solid Oxide Fuel Cells (SOFCs) to 300–600 °C is a great challenge for the development of SOFC. Among the extensive research and development (R&D) efforts that have been done on lowering the operating temperature of SOFCs, nanomaterials have played a critical role in improving ion transportation in electrolytes and facilitating electrochemical catalyzation of the electrodes. This work reviews recent progress in lowering the temperature of SOFCs by using semiconductor-ionic conductor nanomaterial, which is typically a composition of semiconductor and ionic conductor, as a membrane. The historical development, as well as the working mechanism of semiconductor-ionic membrane fuel cell (SIMFC), is discussed. Besides, the development in the application of nanostructured pure ionic conductors, semiconductors, and nanocomposites of semiconductors and ionic conductors as the membrane is highlighted. The method of using nano-structured semiconductor-ionic conductors as a membrane has been proved to successfully exhibit a significant enhancement in the ionic conductivity and power density of SOFCs at low temperatures and provides a new way to develop low-temperature SOFCs. Full article

(This article belongs to the Special Issue Advanced Fuel Cells and Solid Batteries)

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