| 1. |
- Zhang, Yixiao, et al.
(författare)
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A Trajectory Optimization-Based Intersection Coordination Framework for Cooperative Autonomous Vehicles
- 2022
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Ingår i: IEEE transactions on intelligent transportation systems (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1524-9050 .- 1558-0016. ; 23:9, s. 14674-14688
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Tidskriftsartikel (refereegranskat)abstract
- Since vehicles from multiple roads frequently merge at intersections, it formulates a typical traffic bottleneck of modern transportation systems. Proper vehicle coordination and motion plan at road intersections are of importance to guarantee safety as well as improving the traffic throughput, fuel efficiency and so on. In this paper, we try to present a general dedicated intersection coordination framework for autonomous vehicles, where both high- and low-level planners are appropriately designed and integrated. In the high-level planner, two different strategies are formulated to coordinate the autonomous vehicles to generate reference trajectories and feasible ``tunnels'', respectively. Especially, a novel space-time-block based resource allocation scheme is presented to describe the feasible tunnels. Furthermore, to avoid collisions with unexpected obstacles such as pedestrians, bicycles or other vehicles with human drivers, a low-level planner is designed to generate practical trajectories based on the solutions from the high-level planner, according to their local on-board observations. Simulations and practical experiments are carried out, to show that our proposed coordination framework can achieve obvious performance advantages in various traffic metrics, including the throughput, fairness in driving maneuvers and driving comfort, etc. We also find that the high-level planner is effective in eliminating possible deadlocks among autonomous vehicles, which is rarely discussed in existing investigations.
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| 2. |
- Feng, Boya, et al.
(författare)
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Structural and Functional Insights into the Mode of Action of a Universally Conserved Obg GTPase
- 2014
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Ingår i: PLoS biology. - : Public Library of Science (PLoS). - 1544-9173 .- 1545-7885. ; 12:5, s. e1001866-
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Tidskriftsartikel (refereegranskat)abstract
- Obg proteins are a family of P-loop GTPases, conserved from bacteria to human. The Obg protein in Escherichia coli (ObgE) has been implicated in many diverse cellular functions, with proposed molecular roles in two global processes, ribosome assembly and stringent response. Here, using pre-steady state fast kinetics we demonstrate that ObgE is an anti-association factor, which prevents ribosomal subunit association and downstream steps in translation by binding to the 50S subunit. ObgE is a ribosome dependent GTPase; however, upon binding to guanosine tetraphosphate (ppGpp), the global regulator of stringent response, ObgE exhibits an enhanced interaction with the 50S subunit, resulting in increased equilibrium dissociation of the 70S ribosome into subunits. Furthermore, our cryo-electron microscopy (cryo-EM) structure of the 50S? ObgE? GMPPNP complex indicates that the evolutionarily conserved N-terminal domain (NTD) of ObgE is a tRNA structural mimic, with specific interactions with peptidyl-transferase center, displaying a marked resemblance to Class I release factors. These structural data might define ObgE as a specialized translation factor related to stress responses, and provide a framework towards future elucidation of functional interplay between ObgE and ribosome-associated (p) ppGpp regulators. Together with published data, our results suggest that ObgE might act as a checkpoint in final stages of the 50S subunit assembly under normal growth conditions. And more importantly, ObgE, as a (p) ppGpp effector, might also have a regulatory role in the production of the 50S subunit and its participation in translation under certain stressed conditions. Thus, our findings might have uncovered an under-recognized mechanism of translation control by environmental cues.
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| 3. |
- Li, Zhiyang, et al.
(författare)
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Magnetic carbon nanotube modified S-scheme TiO2-x/g-C3N4/CNFe heterojunction coupled with peroxymonosulfate for effective visible-light-driven photodegradation via enhanced interfacial charge separation
- 2023
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Ingår i: Separation and Purification Technology. - : Elsevier. - 1383-5866 .- 1873-3794. ; 308
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Tidskriftsartikel (refereegranskat)abstract
- To remediate water bodies contaminated with organic micropollutants, recyclable and visible-light-driven coupled photocatalysis-peroxymonosulfate (PMS) activation systems were established by synthesizing magnetic-carbon-nanotubes (CNFe) modified TiO2-x/g-C3N4/CNFe (TCNCNFe) S-scheme heterojunction with oxygen vacancies (O-v) by a simple hydrothermal-calcination approach. The introduction of O-v and CNFe enhances the visible-light-harvesting efficiency and the internal electric field across the heterojunction accompanying favorable energy band bending could effectively migrate the photoexcited electrons along the S-scheme mechanism, thus highly suppressing in situ recombination and improving charge separation. Therefore the TCNCNFe-(30-500)/PMS/Vis system achieved 95.4% removal efficiency of atrazine after 30 min irradiation, meanwhile exhibited excellent recyclability without metal ion leaching due to the unique pod-like nanostructure of CNFe. Moreover, the impacts of certain various reaction variables on pollutant removal were explored to evaluate the practical application potential. Interestingly, the biotoxicity of the treated reaction filtrate was significantly alleviated compared to that of ATZ solution. Furthermore, the exploration of photocatalytic reaction mechanism revealed that the dominant reactive oxidizing species contributed in the following order: h(+) > (OH)-O-center dot > O-center dot(2)- > (SO4-)-S-center dot, and the feasible photodegradation pathway of atrazine was presented based on the determined in-termediates. Hence, this research work holds great promise in ecological environment protection using sustainable solar energy.
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| 4. |
- Cai, Yixiao, et al.
(författare)
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Bioderived Calcite as Electrolyte for Solid Oxide Fuel Cells : A Strategy toward Utilization of Waste Shells
- 2017
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 5:11, s. 10387-10395
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Tidskriftsartikel (refereegranskat)abstract
- The excessive consumption of synthesized materials and enhanced environmental protection protocols necessitate the exploitation of desirable functionalities to handle our solid waste. Through a simple calcination and composite strategy, this work envisages the first application of biocalcite derived from the waste of crayfish shells as an electrolyte for solid oxide fuel cells (SOFCs), which demonstrates encouraging performances within a low temperature range of 450-550 degrees C. The single cell device, assembled from calcined waste shells at 600 degrees C (CWS600), enables a peak power density of 166 mW cm(-2) at 550 degrees C, and further renders 330 and 256 mW cm(-2) after compositing with perovskite La0.6Sr0.4Co0.8Fe0.2O3-delta (LSCF) and layer-structured LiNi0.8Co0.15Al0.05O2 (LNCA), respectively. Notably, an oxygen-ion blocking fuel cell is used to confirm the proton-conducting property of CWS600 associated electrolytes. The practical potential of the prepared fuel cells is also validated when the cell voltage of the cell is kept constant value over 10 h during a galvanostatic operation using a CWS600-LSCF electrolyte. These interesting findings may increase the likelihood of transforming our solid municipal waste into electrochemical energy devices, and also importantly, provide an underlying approach for discovering novel electrolytes for low-temperature SOFCs.
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| 5. |
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| 6. |
- Liu, Yanyan, et al.
(författare)
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Superionic Conductivity of Sm3+, Pr3+, and Nd3+ Triple-Doped Ceria through Bulk and Surface Two-Step Doping Approach
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:28, s. 23614-23623
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Tidskriftsartikel (refereegranskat)abstract
- Sufficiently high oxygen ion conductivity of electrolyte is critical for good performance of low-temperature solid oxide fuel cells (LT-SOFCs). Notably, material conductivity, reliability, and manufacturing cost are the major barriers hindering LT-SOFC commercialization. Generally, surface properties control the physical and chemical functionalities of materials. Hereby, we report a Sm3+, Pr3+, and Nd3+ triple-doped ceria, exhibiting the highest ionic conductivity among reported doped-ceria oxides, 0.125 S cm(-1) at 600 degrees C. It was designed using a two-step wet-chemical coprecipitation method to realize a desired doping for Sm3+ at the bulk and Pr3+/Nd3+ at surface domains (abbreviated as PNSDC). The redox couple Pr3+ Pr4+ contributes to the extraordinary ionic conductivity. Moreover, the mechanism for ionic conductivity enhancement is demonstrated. The above findings reveal that a joint bulk and surface doping methodology for ceria is a feasible approach to develop new oxide-ion conductors with high impacts on advanced LT-SOFCs.
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| 7. |
- Lu, Yuzheng, et al.
(författare)
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Progress in Electrolyte-Free Fuel Cells
- 2016
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Ingår i: FRONTIERS IN ENERGY RESEARCH. - : FRONTIERS MEDIA SA. - 2296-598X. ; 4
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Forskningsöversikt (refereegranskat)abstract
- Solid oxide fuel cell (SOFC) represents a clean electrochemical energy conversion technology with characteristics of high conversion efficiency and low emissions. It is one of the most important new energy technologies in the future. However, the manufacture of SOFCs based on the structure of anode/electrolyte/cathode is complicated and time-consuming. Thus, the cost for the entire fabrication and technology is too high to be affordable, and challenges still hinder commercialization. Recently, a novel type of electrolyte-free fuel cell (EFFC) with single component was invented, which could be the potential candidate for the next generation of advanced fuel cells. This paper briefly introduces the EFFC, working principle, performance, and advantages with updated research progress. A number of key R&D issues about EFFCs have been addressed, and future opportunities and challenges are discussed.
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| 8. |
- Wang, Baoyuan, et al.
(författare)
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Fast ionic conduction in semiconductor CeO2-delta electrolyte fuel cells
- 2019
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Ingår i: NPG ASIA MATERIALS. - : Nature Publishing Group. - 1884-4049 .- 1884-4057. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Producing electrolytes with high ionic conductivity has been a critical challenge in the progressive development of solid oxide fuel cells (SOFCs) for practical applications. The conventional methodology uses the ion doping method to develop electrolyte materials, e.g., samarium-doped ceria (SDC) and yttrium-stabilized zirconia (YSZ), but challenges remain. In the present work, we introduce a logical design of non-stoichiometric CeO2-delta based on non-doped ceria with a focus on the surface properties of the particles. The CeO2-delta reached an ionic conductivity of 0.1 S/cm and was used as the electrolyte in a fuel cell, resulting in a remarkable power output of 660 mW/cm(2) at 550 degrees C. Scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) clearly clarified that a surface buried layer on the order of a few nanometers was composed of Ce3+ on ceria particles to form a CeO2-delta@CeO2 core-shell heterostructure. The oxygen deficient layer on the surface provided ionic transport pathways. Simultaneously, band energy alignment is proposed to address the short circuiting issue. This work provides a simple and feasible methodology beyond common structural (bulk) doping to produce sufficient ionic conductivity. This work also demonstrates a new approach to progress from material fundamentals to an advanced low-temperature SOFC technology.
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| 9. |
- Wang, Baoyuan, et al.
(författare)
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Photovoltaic properties of LixCo3-xO4/TiO2 heterojunction solar cells with high open-circuit voltage
- 2016
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 157, s. 126-133
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Tidskriftsartikel (refereegranskat)abstract
- All-oxide solar cells are presently attracting extensive research interest due to their excellent stability, low-cost and non-toxicity. However, the band gap of metal oxides is lack of effective optimization and results in poor photovoltaic performance, thus hindering their practical applications. In this work, Co3O4 was investigated for application as a photo-absorber in all-oxide solar cells, and its band gap was optimized by introducing Li dopant into the spinel structure. LixCo3-xO4 nanoparticles, prepared via the hydrothermal method, were homogenously coated onto TiO2 mesoporous films, which were then used to fabricate planar heterojunction TiO2/LixCo3-xO4 solar cells (SCs). The effects of Li-doping on the heterojunction solar cell performance were further investigated. The findings revealed that the incorporation of Li ions into Co3O4 led to a significant enhancement in short-circuit current density (J(sc)). Remarkably, a high open-circuit voltage (V-oc) of 0.70 V was also achieved. Besides, reasons for the enhanced cell performance are the narrower band gap, reduced photogenerated carrier recombination and the more favorable energy band structure as compared with SCs assembled from pure Co3O4.
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| 10. |
- Xia, Chen, et al.
(författare)
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Electrochemical properties of LaCePr-oxide/K2WO4 composite electrolyte for low-temperature SOFCs
- 2017
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Ingår i: Electrochemistry communications. - : ELSEVIER SCIENCE INC. - 1388-2481 .- 1873-1902. ; 77, s. 44-48
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we introduced tungstate into solid oxide fuel cells (SOFCs) for the first time by using a La/Pr-doped CeO2 (LCP)/K2WO4 composite as the electrolyte, which exhibited remarkably enhanced grain boundary conduction compared to that of single-phase LCP. The composition dependence of the electrical conductivity was investigated. As a result, the composite with 10 wt% K2WO4 was proven to be the optimum ratio, revealing a significantly higher ionic conductivity than LCP, along with a negligible electronic conductivity. The fuel cell using the LCP/K2WO4 electrolyte displayed an encouraging performance of 500 mW cm(-2) at 550 degrees C. These findings indicate that the LCP/K2WO4 composite is a promising electrolyte for low-temperature SOFCs.
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| 11. |
- Xia, Chen, et al.
(författare)
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Industrial-grade rare-earth and perovskite oxide for high-performance electrolyte layer-free fuel cell
- 2016
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Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 307, s. 270-279
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, we report a composite of industrial-grade material LaCePr-oxide (LCP) and perovskite La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) for advanced electrolyte layer-free fuel cells (EFFCs). The microstructure, morphology, and electrical properties of the LCP, LSCF, and LCP-LSCF composite were investigated and characterized by XRD, SEM, EDS, TEM, and EIS. Various ratios of LCP to LSCF in the composite were modulated to achieve balanced ionic and electronic conductivities. Fuel cell with an optimum ratio of 60 wt% LCP to 40 wt% LSCF reached the highest open circuit voltage (OCV) at 1.01 V and a maximum power density of 745 mW cm-2 at 575°C, also displaying a good performance stability. The high performance is attributed to the interfacial mechanisms and electrode catalytic effects. The findings from the present study promote industrial-grade rare-earth oxide as a promising new material for innovative low temperature solid oxide fuel cell (LTSOFC) technology.
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| 12. |
- Xia, Chen, et al.
(författare)
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Natural Mineral-Based Solid Oxide Fuel Cell with Heterogeneous Nanocomposite Derived from Hematite and Rare-Earth Minerals
- 2016
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 8:32, s. 20748-20755
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Tidskriftsartikel (refereegranskat)abstract
- Solid oxide fuel cells (SOFCs) have attracted much attention worldwide because of their potential for providing clean and reliable electric power. However, their commercialization is subject to the high operating temperatures and costs. To make SOFCs more competitive, here we report a novel and attractive nanocomposite hematite LaCePrOx (hematite LCP) synthesized from low-cost natural hematite and LaCePr-carbonate mineral as an electrolyte candidate. This heterogeneous composite exhibits a conductivity as high as 0.116 S cm(-1) at 600 degrees C with an activation energy of 0.50 eV at 400-600 degrees C. For the first time, a fuel cell using such a natural mineral-based composite demonstrates a maximum power density of 625 mW cm(-2) at 600 degrees C and notable power output of 386 mW cm(-2) at 450 degrees C. The extraordinary ionic conductivity and device performances are primarily attributed to the heterophasic interfacial conduction effect of the hematite-LCP composite. These superior properties, along with the merits of ultralow cost, abundant storage, and eco-friendliness, make the new composite a highly promising material for commercial SOFCs.
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| 13. |
- Xia, Chen, et al.
(författare)
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Strategy towards cost-effective low-temperature solid oxide fuel cells : A mixed-conductive membrane comprised of natural minerals and perovskite oxide
- 2017
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Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 342, s. 779-786
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Tidskriftsartikel (refereegranskat)abstract
- Our previous work has revealed the feasibility of natural hematite as an electrolyte material for solid oxide fuel cells (SOFCs), tailoring SOFCs to be a more economically competitive energy conversion technology. In the present work, with the aim of exploring more practical uses of natural minerals, a novel composite hematite/LaCePrOx-La0.6Sr0.4Co0.2Fe0.8O3-δ (hematite/LCP-LSCF) has been developed from natural hematite ore, rare-earth mineral LaCePr-carbonate, and perovskite oxide LSCF as a functional membrane in SOFCs. The heterogeneity, nanostructure and mixed-conductive property of the composite were investigated. The results showed that the hematite/LCP-30 wt% LSCF composite possessed balanced ionic and electronic conductivities, with an ionic conductivity as high as 0.153 S cm−1 at 600 °C. The as-designed fuel cell using the hematite/LCP-LSCF membrane exhibited encouraging power outputs of 303 – 662 mW cm−2 at 500 – 600 °C. These findings show that the hematite/LCP-LSCF based fuel cell is a viable strategy for developing cost-effective and practical low-temperature SOFCs (LTSOFCs).
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| 14. |
- Yang, Junhuai, et al.
(författare)
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Holocene forcing of aeolian dust activity over the Tibetan Plateau and its surroundings
- 2024
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Ingår i: Global and Planetary Change. - 0921-8181 .- 1872-6364. ; 235
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Tidskriftsartikel (refereegranskat)abstract
- Aeolian deposits on the Tibetan Plateau (TP) and its surroundings provide crucial source materials for the Asian dust cycle, which significantly affects Asian and global ecosystems and climate. However, it is unclear how the dust dynamics of the TP and its surroundings are linked to Earth's climate system. To address this issue, we examined the grain size and accumulation rate of six Holocene aeolian sections on the southern TP (a new, well-dated high-resolution section, two relatively low-resolution sections, and three published sections) and combined them with equivalent aeolian sedimentary records from eastern arid central Asia. The results suggest that dust activity in both regions decreased during the early to middle Holocene and then increased in the late Holocene. We hypothesize that the primary drivers of Holocene dust activity in both regions are similar. Cold-season insolation, as the primary driving factor, combined with ice volume and atmospheric CO2 concentration, collectively controlled the regional temperature, which determined the near-surface wind intensity via its influence on the TP High and Siberian High, respectively, thus ultimately controlling the regional dust activity. In this context, we project that dust activity on the TP and its neighboring areas will decrease under warm scenarios in the 21st century. Overall, our findings provide an extensive overview of the past, present, and future scenarios of Asian dust activity, especially of the TP dust.
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| 15. |
- Zhang, Wei, et al.
(författare)
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Mixed ionic-electronic conductor membrane based fuel cells by incorporating semiconductor Ni0.8Co0.15Al0.05LiO2-delta into the Ce0.8Sm0.2O2-delta-Na2CO3 electrolyte
- 2016
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 41:34, s. 15346-15353
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, a novel composite was fabricated by incorporating the semiconductor Ni0.8Co0.15Al0.05LiO2-delta (NCAL) into the ionic electrolyte Ce0.8Sm0.2O2-delta-Na2CO3 (NSDC), and further developed as a mixed-conducting membrane for single layer fuel cell (SLFC) applications. Experimentally, the crystal structure, morphology, chemical composition and thermo-stability of the composite were characterized by XRD, SEM and TGA. The best cell performance was investigated when the NSDC-NCAL membrane was optimized at a weight ratio of 6:4. On this basis, a number of interesting findings were obtained: i) the mixed conducting membrane did not cause any short circuit; on the contrary, the cell reached a decent open circuit voltage (OCV) of similar to 1.0 V. a high power density of 1072 mW cm(-2) was achieved at 550 degrees C for the NSDC-NCAL membrane based cell, which was much better than that using a pure NSDC electrolyte membrane. Electrochemical impedance spectroscopy (EIS) showed that the NSDC-NCAL composite exhibited significantly improved grain boundary conduction and reduced electrode polarizations, contributing to the resultant performance. To consolidate the usefulness of the device, we also conducted the durability test. The above findings indicate the strategy of introducing mixed NSDC-NCAL membrane is feasible for high-performance SLFCs operating at low temperatures.
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| 16. |
- Zhang, Wei, et al.
(författare)
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The fuel cells studies from ionic electrolyte Ce0.8Sm0.05Ca0.15O2-delta to the mixture layers with semiconductor Ni0.8Co0.15Al0.05LiO2-delta
- 2016
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 41:41, s. 18761-18768
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Tidskriftsartikel (refereegranskat)abstract
- The mixture of ionic electrolyte Ce0.8Sm0.05Ca0.15O2-delta (SCDC) and semiconductor Ni0.8Co0.15Al0.05LiO2-delta (NCAL) layers was used for low temperature solid oxide fuel cell (LT-SOFC) applications. Using the as-prepared SCDC-NCAL semiconductor-ionic layer to replace the ionic SCDC electrolyte, following results have been obtained: the SCDC electrolyte fuel cell reached a lower voltage, 1.05 V, and lower power output, 415 mW cm(-2), compared to that using the semiconductor-ionic layer, 1.06 V and 617 mW cm(-2) at 550 degrees C. The electrochemical impedance spectroscopy (EIS) was applied to investigate the electrochemical processes of the device; X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM) for the microstructure and morphology of the as-prepared materials. The results have illuminated that the introduction of semiconductor into ionic electrolyte could make extended triple phase boundary (TPB) area, which can provide more active sites to accelerate the fuel cell reactions and enhance the cell performance. Furthermore, we also discovered that the ionic SCDC and electronic NCAL should be in an appropriate composition to achieve a balanced ionic and electronic conductivity, which is the key issue for high performance semiconductor-ionic fuel cells.
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