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Multiplying Oxygen Permeability of a Ruddlesden-Popper Oxide by Orientation Control via Magnets. Angew Chem Int Ed Engl 2024; 63:e202312473. [PMID: 37987465 DOI: 10.1002/anie.202312473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 11/10/2023] [Accepted: 11/20/2023] [Indexed: 11/22/2023]
Abstract
Ruddlesden-Popper-type oxides exhibit remarkable chemical stability in comparison to perovskite oxides. However, they display lower oxygen permeability. We present an approach to overcome this trade-off by leveraging the anisotropic properties of Nd2 NiO4+δ . Its (a,b)-plane, having oxygen diffusion coefficient and surface exchange coefficient several orders of magnitude higher than its c-axis, can be aligned perpendicular to the gradient of oxygen partial pressure by a magnetic field (0.81 T). A stable and high oxygen flux of 1.40 mL min-1 cm-2 was achieved for at least 120 h at 1223 K by a textured asymmetric disk membrane with 1.0 mm thickness under the pure CO2 sweeping. Its excellent operational stability was also verified even at 1023 K in pure CO2 . These findings highlight the significant enhancement in oxygen permeation membrane performance achievable by adjusting the grain orientation. Consequently, Nd2 NiO4+δ emerges as a promising candidate for industrial applications in air separation, syngas production, and CO2 capture under harsh conditions.
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2
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Recycling and Reusing of Graphite from Retired Lithium-ion Batteries: A Review. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2308494. [PMID: 38102959 DOI: 10.1002/adma.202308494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 10/28/2023] [Indexed: 12/17/2023]
Abstract
The proliferation of rechargeable lithium-ion batteries (LIBs) over the past decade has led to a significant increase in the number of electric vehicles (EVs) powered by these batteries reaching the end of their lifespan. With retired EVs becoming more prevalent, recycling and reusing their components, particularly graphite, has become imperative as the world transitions toward electric mobility. Graphite constitutes ≈20% of LIBs by weight, making it a valuable resource to be conserved. This review presents an in-depth analysis of the current global graphite mining landscape and explores potential opportunities for the "second life" of graphitefrom depleted LIBs. Various recycling and reactivation technologies in both industry and academia are discussed, along with potential applications for recycled graphite forming a vital aspect of the waste management hierarchy. Furthermore, this review addresses the future challenges faced by the recycling industry in dealing with expired LIBs, encompassing environmental, economic, legal, and regulatory considerations. In conclusion, this review provides a comprehensive overview of the developments in recycling and reusing graphite from retired LIBs, offering valuable insights for forthcoming large-scale recycling efforts.
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Hydrogen-Tolerant La 0.6Ca 0.4Co 0.2Fe 0.8O 3-d Oxygen Transport Membranes from Ultrasonic Spray Synthesis for Plasma-Assisted CO 2 Conversion. MEMBRANES 2023; 13:875. [PMID: 37999361 PMCID: PMC10673528 DOI: 10.3390/membranes13110875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 11/03/2023] [Accepted: 11/05/2023] [Indexed: 11/25/2023]
Abstract
La0.6Ca0.4Co1-xFexO3-d in its various compositions has proven to be an excellent CO2-resistant oxygen transport membrane that can be used in plasma-assisted CO2 conversion. With the goal of incorporating green hydrogen into the CO2 conversion process, this work takes a step further by investigating the compatibility of La0.6Ca0.4Co1-xFexO3-d membranes with hydrogen fed into the plasma. This will enable plasma-assisted conversion of the carbon monoxide produced in the CO2 reduction process into green fuels, like methanol. This requires the La0.6Ca0.4Co1-xFexO3-d membranes to be tolerant towards reducing conditions of hydrogen. The hydrogen tolerance of La0.6Ca0.4Co1-xFexO3-d (x = 0.8) was studied in detail. A faster and resource-efficient route based on ultrasonic spray synthesis was developed to synthesise the La0.6Ca0.4Co0.2Fe0.8O3-d membranes. The La0.6Ca0.4Co0.2Fe0.8O3-d membrane developed using ultrasonic spray synthesis showed similar performance in terms of its oxygen permeation when compared with the ones synthesised with conventional techniques, such as co-precipitation, sol-gel, etc., despite using 30% less cobalt.
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Quantitative Characterization of Local Thermal Properties in Thermoelectric Ceramics Using "Jumping-Mode" Scanning Thermal Microscopy. SMALL METHODS 2023; 7:e2201516. [PMID: 36775977 DOI: 10.1002/smtd.202201516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 01/07/2023] [Indexed: 06/18/2023]
Abstract
Thermoelectric conversion may take a significant share in future energy technologies. Oxide-based thermoelectric composite ceramics attract attention for promising routes for control of electrical and thermal conductivity for enhanced thermoelectric performance. However, the variability of the composite properties responsible for the thermoelectric performance, despite nominally identical preparation routes, is significant, and this cannot be explained without detailed studies of thermal transport at the local scale. Scanning thermal microscopy (SThM) is a scanning probe microscopy method providing access to local thermal properties of materials down to length scales below 100 nm. To date, realistic quantitative SThM is shown mostly for topographically very smooth materials. Here, methods for SThM imaging of bulk ceramic samples with relatively rough surfaces are demonstrated. "Jumping mode" SThM (JM-SThM), which serves to preserve the probe integrity while imaging rough surfaces, is developed and applied. Experiments with real thermoelectric ceramics show that the JM-SThM can be used for meaningful quantitative imaging. Quantitative imaging is performed with the help of calibrated finite-elements model of the SThM probe. The modeling reveals non-negligible effects associated with the distributed nature of the resistive SThM probes used; corrections need to be made depending on probe-sample contact thermal resistance and probe current frequency.
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A facile strategy for reclaiming discarded graphite and harnessing the rate capabilities of graphite anodes. JOURNAL OF HAZARDOUS MATERIALS 2023; 445:130607. [PMID: 37056017 DOI: 10.1016/j.jhazmat.2022.130607] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 11/29/2022] [Accepted: 12/12/2022] [Indexed: 06/19/2023]
Abstract
Graphite negative electrodes are unbeaten hitherto in lithium-ion batteries (LiBs) due to their unique chemical and physical properties. Thus, the increasing scarcity of graphite resources makes smart recycling or repurposing of discarded graphite particularly imperative. However, the current recycling techniques still need to be improved upon with urgency. Herein a facile and efficient hydrometallurgical process is reported to effectively regenerate aged (39.5 %, 75 % state-of-health, SOH) scrapped graphite (SG) from end-of-life lithium-ion batteries. Ultimately, the first cycle reversible capacity of SG1 (SOH = 39.5 %) improved from 266 mAh/g to 337 mAh/g while 330 mAh/g (98 %) remain after 100 cycles at 0.5 C. The reversible capacity for the first cycle of SG2 (SOH = 75 %) boosted from 335 mAh/g to 366 mAh/g with the capacity retention of 99.3 % after 100 cycles at 0.5 C, which is comparable with the benchmark commercial graphite. The regenerated graphites RG1 and RG2 exhibit excellent output characteristics even increasing the rate up to 4 C. This is the best rate level reported in the literature to date. Finally, the diffusion coefficient of Li ions during deintercalation and intercalation in the regenerated graphites have been measured by galvanostatic intermittent titration technique (GITT), determining values 2 orders-of-magnitude higher than that of the spent counterparts. Taking advantage of the synergistic effect of acid leaching and heat treatment, this strategy provides a simple and up-scalable method to recycle graphitic anodes.
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Single‐source‐precursor derived bulk Si3N4/HfBxN1‐x ceramic nanocomposites with excellent oxidation resistance. Z Anorg Allg Chem 2022. [DOI: 10.1002/zaac.202200203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Shielding Protection by Mesoporous Catalysts for Improving Plasma-Catalytic Ambient Ammonia Synthesis. J Am Chem Soc 2022; 144:12020-12031. [PMID: 35731953 PMCID: PMC9284550 DOI: 10.1021/jacs.2c01950] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
Plasma catalysis
is a promising technology for decentralized small-scale
ammonia (NH3) synthesis under mild conditions using renewable
energy, and it shows great potential as an alternative to the conventional
Haber–Bosch process. To date, this emerging process still suffers
from a low NH3 yield due to a lack of knowledge in the
design of highly efficient catalysts and the in situ plasma-induced
reverse reaction (i.e., NH3 decomposition). Here, we demonstrate
that a bespoke design of supported Ni catalysts using mesoporous MCM-41
could enable efficient plasma-catalytic NH3 production
at 35 °C and 1 bar with >5% NH3 yield at 60 kJ/L.
Specifically, the Ni active sites were deliberately deposited on the
external surface of MCM-41 to enhance plasma–catalyst interactions
and thus NH3 production. The desorbed NH3 could
then diffuse into the ordered mesopores of MCM-41 to be shielded from
decomposition due to the absence of plasma discharge in the mesopores
of MCM-41, that is, “shielding protection”, thus driving
the reaction forward effectively. This promising strategy sheds light
on the importance of a rational design of catalysts specifically for
improving plasma-catalytic processes.
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8
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Hot-Water Hemicellulose Extraction from Fruit Processing Residues. ACS OMEGA 2022; 7:13436-13447. [PMID: 35559167 PMCID: PMC9088762 DOI: 10.1021/acsomega.1c06055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 03/18/2022] [Indexed: 06/15/2023]
Abstract
Hemicelluloses are an abundant biopolymer resource with interesting properties for applications in coatings and composite materials. The objective of this investigation was to identify variables of industrially relevant extraction processes that increase the purity of hemicelluloses extracted from fruit residues. Our main finding is that extraction with subcritical water, followed by precipitation with alcohol, can be adjusted to yield products with a purity of at least 90%. Purity was determined based on the total concentration of glucose, galactose, xylose, arabinose, and mannose after hydrolysis with sulfuric acid. In the first experimental design (DoE methodology), the effects of extraction temperature (95-155 °C) and time (20-100 min) on yield and purity were studied. A clear trade-off between yield and purity was observed at high temperatures, indicating the selective removal of impurities. In the second experimental design, the influence of extract pH and alcohol concentration on yield and purity was investigated for the raw extract and a concentrate of this extract with 1/6 of the original volume. The concentrate was obtained by ultrafiltration through ceramic hollow-fiber membranes. The highest purity of 96% was achieved with the concentrate after precipitating with 70% alcohol. Key factors for the resource efficiency of the overall process are addressed. It is concluded that extraction with subcritical water and ultrafiltration are promising technologies for producing hemicelluloses from fruit residues for material applications.
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Cover Feature: Oxygen‐Functionalized Boron Nitride for the Oxidative Dehydrogenation of Propane – The Case for Supported Liquid Phase Catalysis (ChemCatChem 8/2022). ChemCatChem 2022. [DOI: 10.1002/cctc.202200379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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10
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Berichtigung: Ganzheitliche Betrachtung in der Materialentwicklung: Wasser‐Elektrolyse als Fallbeispiel. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202201854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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11
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Oxygen‐functionalized Boron Nitride for the Oxidative Dehydrogenation of Propane – The case for supported liquid phase catalysis. ChemCatChem 2022. [DOI: 10.1002/cctc.202200068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Natural wood templated hierarchically cellular NbC/Pyrolytic carbon foams as Stiff, lightweight and High-Performance electromagnetic shielding materials. J Colloid Interface Sci 2022; 606:1543-1553. [PMID: 34500157 DOI: 10.1016/j.jcis.2021.08.110] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/15/2021] [Accepted: 08/16/2021] [Indexed: 10/20/2022]
Abstract
Hierarchically cellular, stiff, and lightweight niobium carbide (NbC)-pyrolytic carbon (PyC) monolithic foam composites possessing excellent electromagnetic interference shielding effectiveness (EMI SE) were developed via a natural wood template-based method. Pyrolytic carbon derived from the decomposed cellulose in the wood worked as the carbon source for the growth of NbC phase, and the NbC-PyC heterogeneous nano-interface formed between the residual PyC and the freshly formed NbC. Multi-loss mechanisms (e.g. conductive loss, dipole polarization loss, and especially interface polarization loss) were established by controlling the NbC content and residual PyC phase in the NbC-PyC foams, which significantly improved the absorption capability. Compared to 28.0 dB of PyC monolith, the EMI SE of NbC-PyC foam can reach 54.8 dB when the thickness is 0.5 mm, which outperforms the other porous-based shielding materials. Due to the highly porous structure of pristine wood, the resulting NbC-PyC foam exhibited a low density of 0.48 g/cm3, which is ~ 1/16 of dense NbC (7.78 g/cm3). Generally, this work introduces innovative ideas for designing novel and advanced transition metal carbide-carbon composite materials.
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A comprehensive comparative study of CO2-resistance and oxygen permeability of 60 wt % Ce0.8M0.2O2– (M = La, Pr, Nd, Sm, Gd) - 40 wt % La0.5Sr0.5Fe0.8Cu0.2O3– dual-phase membranes. J Memb Sci 2021. [DOI: 10.1016/j.memsci.2021.119783] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Holistic View on Materials Development: Water Electrolysis as a Case Study. Angew Chem Int Ed Engl 2021; 60:20094-20100. [PMID: 34235841 PMCID: PMC8457090 DOI: 10.1002/anie.202105324] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Indexed: 11/20/2022]
Abstract
In view of rising ecological awareness, materials development is primarily aimed at improving the performance and efficiency of innovative and more elaborate materials. However, a materials performance figure of merit should include essential aspects of materials: environmental impact, economic constraints, technical feasibility, etc. Thus, we promote the inclusion of sustainability criteria already during the materials design process. With such a holistic design approach, new products may be more likely to meet the circular economy requirements than when traditional development strategies are pursued. Using catalysts for water electrolysis as an example, we present a modelling method based on experimental data to holistically evaluate processes.
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Ganzheitliche Betrachtung in der Materialentwicklung: Wasser‐Elektrolyse als Fallbeispiel. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202105324] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Effects of Doping Ni on the Microstructures and Thermoelectric Properties of Co-Excessive NbCoSn Half-Heusler Compounds. ACS APPLIED MATERIALS & INTERFACES 2021; 13:34533-34542. [PMID: 34279070 DOI: 10.1021/acsami.1c08127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The half-Heusler (HH) compound NbCoSn with 18 valence electrons is a promising thermoelectric (TE) material due to its appropriate electrical properties as well as its suitable thermal and chemical stability. Nowadays, doping/substitution and tailoring of microstructures are common experimental approaches to enhance the TE performance of HH compounds. However, detailed theoretical insights into the effects of doping on the microstructures and TE properties are still missing. In this work, the microstructure of NbCoSn was tailored through precipitating the full-Heusler phases in the matrix by changing the nominal ratio of Co and Ni on the Co sites, focusing on the resulting TE properties. Further, first-principles calculations were employed to understand the relationship between the microstructure and the TE properties from the thermodynamic point of view. Detailed analysis of the electronic structure reveals that the presence of excess Co/Ni contributes to the increasing carrier concentration. Through an increase in the electrical conductivity and a reduction in the thermal conductivity, the TE performance is improved. Therefore, the present work offers a new pathway and insights to enhance the TE properties by modifying the microstructure of HH compounds via tailoring the chemical compositions.
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Publisher Correction: Tailoring of an unusual oxidation state in a lanthanum tantalum(IV) oxynitride via precursor microstructure design. Commun Chem 2020. [DOI: 10.1038/s42004-020-0280-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Abstract
Abstract
Perovskite-type oxynitrides AB(O,N)3 are potential candidates for photoelectrode materials in solar water splitting. A drawback of these materials is their low sintering tendency resulting in low electrical conductivities. Typically, they are prepared by ammonia treatment of insulating, wide band gap oxides. In this study, we propose an approach starting from small band gap oxides Eu1−x
Ca
x
TiO3−
δ
and then widen the band gaps in a controlled way by ammonolysis and partial Ca2+ substitution. Both together induced a distortion of the octahedral network and dilution of the Eu4f and N2p levels in the valence band. The effect is the stronger the more Ca2+ is present. Within the series of samples, Eu0.4Ca0.6Ti(O,N)3 had the most suitable optical band gap (EG
≈ 2.2 eV) for water oxidation. However, its higher Eu content compared to Eu0.1Ca0.9Ti(O,N)3 slowed down the charge carrier dynamics due to enhanced trapping and recombination as expressed by large accumulation (τ
on) and decay (τ
off) times of the photovoltage of up to 109 s and 486 s, respectively. In contrast, the highly Ca2+-substituted samples (x ≥ 0.7) were more prone to formation of TiN and oxygen vacancies also leading to Ti3+ donor levels below the conduction band. Therefore, a precise control of the ammonolysis temperature is essential, since even small amounts of TiN can suppress the photovoltage generation by fast recombination processes. Water oxidation tests on Eu0.4Ca0.6Ti(O,N)3 revealed a formation of 7.5 μmol O2 from 50 mg powder together with significant photocorrosion of the bare material. Combining crystal structure, chemical composition, and optical and electronical band gap data, a first simplified model of the electronical band structure of Eu1−x
Ca
x
Ti(O,N)3 could be proposed.
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Realizing p-type NbCoSn half-Heusler compounds with enhanced thermoelectric performance via Sc substitution. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2020; 21:122-130. [PMID: 32165991 PMCID: PMC7054941 DOI: 10.1080/14686996.2020.1726715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 02/04/2020] [Accepted: 02/04/2020] [Indexed: 06/10/2023]
Abstract
N-type half-Heusler NbCoSn is a promising thermoelectric material due to favourable electronic properties. It has attracted much attention for thermoelectric applications while the desired p-type NbCoSn counterpart shows poor thermoelectric performance. In this work, p-type NbCoSn has been obtained using Sc substitution at the Nb site, and their thermoelectric properties were investigated. Of all samples, Nb0.95Sc0.05CoSn compound shows a maximum power factor of 0.54 mW/mK2 which is the highest among the previously reported values of p-type NbCoSn. With the suppression of thermal conductivity, p-type Nb0.95Sc0.05CoSn compound shows the highest measured figure of merit ZT = 0.13 at 879 K.
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Novel CO2-tolerant dual-phase Ce0.9Pr0.1O2– - La0.5Sr0.5Fe0.9Cu0.1O3– membranes with high oxygen permeability. J Memb Sci 2020. [DOI: 10.1016/j.memsci.2019.117530] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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21
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Tailoring of an unusual oxidation state in a lanthanum tantalum(IV) oxynitride via precursor microstructure design. Commun Chem 2019. [DOI: 10.1038/s42004-019-0237-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
AbstractPerovskite-type oxynitrides hold great potential for optical applications due to their excellent visible light absorption properties. However, only a limited number of such oxynitrides with modulated physical properties are available to date and therefore alternative fabrication strategies are needed to be developed. Here, we introduce such an alternative strategy involving a precursor microstructure controlled ammonolysis. This leads to the perovskite family member LaTa(IV)O2N containing unusual Ta4+ cations. The adjusted precursor microstructures as well as the ammonia concentration are the key parameters to precisely control the oxidation state and O:N ratio in LaTa(O,N)3. LaTa(IV)O2N has a bright red colour, an optical bandgap of 1.9 eV and a low (optically active) defect concentration. These unique characteristics make this material suitable for visible light-driven applications and the identified key parameters will set the terms for the targeted development of further promising perovskite family members.
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22
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A CO and CO2 tolerating (La0.9Ca0.1)2(Ni0.75Cu0.25)O4+δ Ruddlesden-Popper membrane for oxygen separation. Front Chem Sci Eng 2019. [DOI: 10.1007/s11705-019-1886-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Exploring Tantalum as a Potential Dopant to Promote the Thermoelectric Performance of Zinc Oxide. MATERIALS 2019; 12:ma12132057. [PMID: 31248011 PMCID: PMC6651819 DOI: 10.3390/ma12132057] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 06/19/2019] [Accepted: 06/25/2019] [Indexed: 11/16/2022]
Abstract
Zinc oxide (ZnO) has being recognised as a potentially interesting thermoelectric material, allowing flexible tuning of the electrical properties by donor doping. This work focuses on the assessment of tantalum doping effects on the relevant structural, microstructural, optical and thermoelectric properties of ZnO. Processing of the samples with a nominal composition Zn1-xTaxO by conventional solid-state route results in limited solubility of Ta in the wurtzite structure. Electronic doping is accompanied by the formation of other defects and dislocations as a compensation mechanism and simultaneous segregation of ZnTa2O6 at the grain boundaries. Highly defective structure and partial blocking of the grain boundaries suppress the electrical transport, while the evolution of Seebeck coefficient and band gap suggest that the charge carrier concentration continuously increases from x = 0 to 0.008. Thermal conductivity is almost not affected by the tantalum content. The highest ZT~0.07 at 1175 K observed for Zn0.998Ta0.002O is mainly provided by high Seebeck coefficient (-464 V/K) along with a moderate electrical conductivity of ~13 S/cm. The results suggest that tantalum may represent a suitable dopant for thermoelectric zinc oxide, but this requires the application of specific processing methods and compositional design to enhance the solubility of Ta in wurtzite lattice.
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25
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Nitrogen Transfer between Solid Phases in the System Mn-N Detected via in situ Neutron Diffraction. Z Anorg Allg Chem 2017. [DOI: 10.1002/zaac.201700304] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Band structure modification of the thermoelectric Heusler-phase TiFe 2Sn via Mn substitution. Phys Chem Chem Phys 2017; 19:18273-18278. [PMID: 28696469 DOI: 10.1039/c7cp02744c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Doping (or substitution)-induced modification of the electronic structure to increase the electronic density of states (eDOS) near the Fermi level is considered as an effective strategy to enhance the Seebeck coefficient, and may consequently boost the thermoelectric performance. Through density-functional theory calculations of Mn-substituted TiFe2-xMnxSn compounds, we demonstrate that the d-states of the substituted Mn atoms induce a strong resonant level near the Fermi energy. Our experimental results are in good agreement with the calculations. They show that Mn substitution results in a large increase of the Seebeck coefficient, arising from an enhanced eDOS in Heusler compounds. The results prove that a proper substitution position and element selection can increase the eDOS, leading to a higher Seebeck coefficient and thermoelectric performance of ecofriendly materials.
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Abstract
One-dimensional Haldane gap materials, such as the rare earth barium chain nickelates, have received great interest due to their vibrant one-dimensional spin antiferromagnetic character and unique structure. Herein we report how these 1D structural features can also be highly beneficial for thermoelectric applications by analysis of the system CaxBaGd2-xNiO5 0 ≤ x ≤ 0.25. Attractive Seebeck coefficients of 140-280 μV K-1 at 350-1300 K are retained even at high acceptor-substitution levels, provided by the interplay of low dimensionality and electronic correlations. Furthermore, the highly anisotropic crystal structure of Haldane gap materials allows very low thermal conductivities, reaching only 1.5 W m-1 K-1 at temperatures above 1000 K, one of the lowest values currently documented for prospective oxide thermoelectrics. Although calcium substitution in BaGd2NiO5 increases the electrical conductivity up to 5-6 S cm-1 at 1150 K < T < 1300 K, this level remains insufficient for thermoelectric applications. Hence, the combination of highly promising Seebeck coefficients and low thermal conductivities offered by this 1D material type underscores a potential new structure type for thermoelectric materials, where the main challenge will be to engineer the electronic band structure and, probably, microstructural features to further enhance the mobility of the charge carriers.
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Tailoring the structure and thermoelectric properties of BaTiO3via Eu2+ substitution. Phys Chem Chem Phys 2017; 19:13469-13480. [DOI: 10.1039/c7cp00020k] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The presence of filled Eu2+ 4f states at the top of the valence band significantly affect the electrical transport properties of Ba1−xEuxTiO3−δ compounds.
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Controlled Design of Functional Nano-Coatings: Reduction of Loss Mechanisms in Photoelectrochemical Water Splitting. ACS APPLIED MATERIALS & INTERFACES 2016; 8:12149-12157. [PMID: 27159411 DOI: 10.1021/acsami.6b01129] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Efficient water splitting with photoelectrodes requires highly performing and stable photoactive materials. Since there is no material known which fulfills all these requirements because of various loss mechanisms, we present a strategy for efficiency enhancement of photoanodes via deposition of functional coatings in the nanometer range. Origins of performance losses in particle-based oxynitride photoanodes were identified and specifically designed coatings were deposited to address each loss mechanism individually. Amorphous TiO2 located at interparticle boundaries enables high electron conductivity. A thin layer of amorphous Ta2O5 can be used as protection layer for photoanodes because of its hole conductivity and thermal and chemical stability. An amorphous layer of NiOx and Co(OH)2 reduces photocorrosion or increases water oxidation kinetics because they act as a hole-capture material or water oxidation catalyst, respectively. Crystalline CoOx nanoparticles increase photocurrent and reduce the onset potential due to enhanced charge separation. The combination of all coatings deposited by a scalable, mild, and reproducible step-by-step approach leads to high-performance oxynitride-based photoanodes providing a maximum photocurrent of 2.52 mA/cm(2) at 1.23 VRHE under AM1.5G illumination.
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Multiband Transport in CoSb 3 Prepared by Rapid Solidification. Z Anorg Allg Chem 2016; 641:2020-2028. [PMID: 26924860 PMCID: PMC4744946 DOI: 10.1002/zaac.201500179] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 09/16/2015] [Indexed: 12/05/2022]
Abstract
Nano‐grained CoSb3 was prepared by melt‐spinning and subsequent spark plasma sintering. The phonon thermal conductivity of skutterudites is known to be sensitive to the kind and the amount of guest atoms. Thus, unfilled CoSb3 can serve as model compound to study the impact of a nanostructure on the thermoelectric properties, especially the phonon thermal conductivity. Therefore, a series of materials was prepared differing only by the cooling speed during the quenching procedure. In contrast to clathrates, the microstructure of meltspun CoSb3 was found to be sensitive to the cooling speed. Although the phonon thermal conductivity, studied by means of Flash and 3ω measurements, was found to be correlated with the grain size, the bulk density of the sintered materials had an even stronger impact. Interestingly, the reduced bulk density did not result in an increased electrical resistivity. The influence of Sb and CoSb2 as foreign phase on the electronic properties of CoSb3 was revealed by a multi‐band Hall effect analysis. While CoSb2 increases the charge carrier density, the influence of the highly mobile charge carriers introduced by elemental Sb on the thermoelectric properties of the composite offer an interesting perspective for the preparation of efficient thermoelectric composite materials.
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Methanol steam reforming catalysts derived by reduction of perovskite-type oxides LaCo1−x−yPdxZnyO3±δ. Catal Sci Technol 2016. [DOI: 10.1039/c5cy01410g] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pd–Zn nanoparticles are synthesized by reduction of LaCo1−x−yPdxZnyO3±δ for methanol steam reforming and they can be reintegrated into the perovskite crystal on reoxidation.
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Enhanced thermoelectric performance of β-Zn4Sb3 based nanocomposites through combined effects of density of states resonance and carrier energy filtering. Sci Rep 2015; 5:17803. [PMID: 26666813 PMCID: PMC4678945 DOI: 10.1038/srep17803] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 11/06/2015] [Indexed: 11/17/2022] Open
Abstract
It is a major challenge to elevate the thermoelectric figure of merit ZT of materials through enhancing their power factor (PF) and reducing the thermal conductivity at the same time. Experience has shown that engineering of the electronic density of states (eDOS) and the energy filtering mechanism (EFM) are two different effective approaches to improve the PF. However, the successful combination of these two methods is elusive. Here we show that the PF of β-Zn4Sb3 can greatly benefit from both effects. Simultaneous resonant distortion in eDOS via Pb-doping and energy filtering via introduction of interface potentials result in a ~40% increase of PF and an approximately twofold reduction of the lattice thermal conductivity due to interface scattering. Accordingly, the ZT of β-Pb0.02Zn3.98Sb3 with 3 vol.% of Cu3SbSe4 nanoinclusions reaches a value of 1.4 at 648 K. The combination of eDOS engineering and EFM would potentially facilitate the development of high-performance thermoelectric materials.
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Design Guidelines for High-Performance Particle-Based Photoanodes for Water Splitting: Lanthanum Titanium Oxynitride as a Model. CHEMSUSCHEM 2015; 8:3451-3458. [PMID: 26360811 DOI: 10.1002/cssc.201500830] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Indexed: 06/05/2023]
Abstract
Semiconductor powders are perfectly suited for the scalable fabrication of particle-based photoelectrodes, which can be used to split water using the sun as a renewable energy source. This systematic study is focused on variation of the electrode design using LaTiO2 N as a model system. We present the influence of particle morphology on charge separation and transport properties combined with post-treatment procedures, such as necking and size-dependent co-catalyst loading. Five rules are proposed to guide the design of high-performance particle-based photoanodes by adding or varying several process steps. We also specify how much efficiency improvement can be achieved using each of the steps. For example, implementation of a connectivity network and surface area enhancement leads to thirty times improvement in efficiency and co-catalyst loading achieves an improvement in efficiency by a factor of seven. Some of these guidelines can be adapted to non-particle-based photoelectrodes.
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From Occupied Voids to Nanoprecipitates: Synthesis of Skutterudite Nanocomposites in situ. Z Anorg Allg Chem 2015. [DOI: 10.1002/zaac.201500137] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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The electrodeposition of FeCrNi stainless steel: microstructural changes induced by anode reactions. Phys Chem Chem Phys 2014; 16:26375-84. [PMID: 25367332 DOI: 10.1039/c4cp03744h] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The FeCrNi alloy, whose composition is close to that of stainless steel 304, was prepared by electrodeposition and characterized. Nanocrystalline FeCrNi (nc-FeCrNi) was obtained by employing a double-compartment cell where the anode is separated from the cathode compartment, while amorphous FeCrNi (a-FeCrNi) was deposited in a conventional single electrochemical cell. The carbon content of nc-FeCrNi was found to be significantly lower than that of a-FeCrNi, suggesting that carbon inclusion is responsible for the change in the microstructure. The major source of carbon is associated with the reaction compounds at the anode electrode, presumably decomposed glycine. Crystal structure analysis by XRD and TEM revealed that the as-deposited nc-FeCrNi deposits consist of α-Fe which transforms to γ-Fe upon thermal annealing. Nanoindentation tests showed that nc-FeCrNi exhibits higher hardness than a-FeCrNi, which is consistent with the inverse Hall-Petch behavior.
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Towards a high thermoelectric performance in rare-earth substituted SrTiO3: effects provided by strongly-reducing sintering conditions. Phys Chem Chem Phys 2014; 16:26946-54. [DOI: 10.1039/c4cp04127e] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Optical and transport properties of LaTi1−xMx(O,N)3±δ (x=0; 0.1, M=Nb5+, W6+) thin films prepared by plasma ammonolysis. J SOLID STATE CHEM 2014. [DOI: 10.1016/j.jssc.2013.12.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Inside Back Cover: Size and Shape-controlled Pd Nanocrystals on ZnO and SiO 2: When the Nature of the Support Determines the Active Phase (ChemCatChem 3/2014). ChemCatChem 2014. [DOI: 10.1002/cctc.201490019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Size and Shape-controlled Pd Nanocrystals on ZnO and SiO2: When the Nature of the Support Determines the Active Phase. ChemCatChem 2014. [DOI: 10.1002/cctc.201301043] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Surface deformations as a necessary requirement for resistance switching at the surface of SrTiO3:N. NANOTECHNOLOGY 2013; 24:475701. [PMID: 24176802 DOI: 10.1088/0957-4484/24/47/475701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Atomic force microscopy (AFM), conductive AFM and electrochemical strain microscopy were used to study the topography change at the defect surface of SrTiO3:N, breakdown in the electrical conduction of the tip/sample/electrode system and ionic motion. The IV curves show resistance switching behavior in a voltage range ±6 V < U <± 10 V and a current of maximum ±10 nA. A series of sweeping IV curves resulted in an increase in ionically polarized states (surface charging), electrochemical volume (surface deformations) and sequential formations of stable surface protrusions. The surface deformations are reversible (U <± 5 V) without IV pinched hysteresis and remained stable during the resistance switching (U >± 6 V), revealing the additional necessity (albeit insufficient due to 50% yield of working cells) of surface protrusion formation for resistance switching memory.
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Electrochemical growth of ZnO nanowires on atomic layer deposition coated polystyrene sphere templates. Electrochim Acta 2013. [DOI: 10.1016/j.electacta.2013.04.168] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Abstract
ABSTRACTAs an approach to improve the thermoelectric properties of the polycrystalline Ca3Co4O9 misfit-layered oxide, substitutions of Co2+…4+ with the heavier cations Ru3+/4+ and In3+ were tested. Polycrystalline samples Ca3Co4-xRuxO9 and Ca3Co4-xInxO9 (0 < x < 0.21) were prepared via a solid-state-reaction route. For each sample the crystal structure was analyzed and a complete thermoelectric characterization was done within a temperature range of 300 K < T < 1125 K.Both substitution strategies resulted in a significant decrease of the thermal conductivity (κ). For the In3+-substituted samples the decrease of the Seebeck coefficient (α) balanced the κ reduction so that no overall enhancement of the figure of merit (ZT) was found. The Ru3+/4+ substitution reduced the p-type carrier concentration and thus increases the electrical resistivity (ρel), while α became larger at low temperatures. Despite the reduction of the power factor, a small enhancement in ZT was observed in the case of x = 0.1 Ru substitution, due to the strong κ reduction. Considering the observed preferred orientation of the Ru-substituted crystallites, a maximum value of ZT = 0.14 perpendicular to the pressing direction is found at T = 1125 K, indicating that Ru substitution is a promising strategy for a further ZT improvement.
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Influence of the synthesis method on the structure of Pd-substituted perovskite catalysts for methane oxidation. Catal Today 2013. [DOI: 10.1016/j.cattod.2012.10.026] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Synchrotron high energy X-ray methods coupled to phase sensitive analysis to characterize aging of solid catalysts with enhanced sensitivity. Phys Chem Chem Phys 2013; 15:8629-39. [PMID: 23657925 DOI: 10.1039/c3cp44638g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
X-ray absorption spectroscopy and X-ray diffraction are suitable probes of the chemical state of a catalyst under working conditions but are limited to bulk information. Here we show in two case studies related to hydrothermal aging and chemical modification of model automotive catalysts that enhanced detailed information of structural changes can be obtained when the two methods are combined with a concentration modulated excitation (cME) approach and phase sensitive detection (PSD). The catalysts are subject to a modulation experiment consisting of the periodic variation of the gas feed composition to the catalyst and the time-resolved data are additionally treated by PSD. In the case of a 2 wt% Rh/Al2O3 catalyst, a very small fraction (ca. 2%) of Rh remaining exposed at the alumina surface after hydrothermal aging at 1273 K can be detected by PSD. This Rh is sensitive to the red-ox oscillations of the experiment and is likely responsible for the observed catalytic activity and selectivity during NO reduction by CO. In the case of a 1.6 wt% Pd/Al2O3-Ce(1-x)Zr(x)O2 catalyst, preliminary results of cME-XRD demonstrate that access to the kinetics of the whole material at work can be obtained. Both the red-ox processes involving the oxygen storage support and the Pd component can be followed with great precision. PSD enables the differentiation between Pd deposited on Al2O3 or on Ce(1-x)Zr(x)O2. Modification of the catalyst by phosphorous clearly induces loss of the structural dynamics required for oxygen storage capacity that is provided by the Ce(4+)/Ce(3+) pair. The two case studies demonstrate that detailed kinetics of subtle changes can be uncovered by the combination of in situ X-ray absorption and high energy diffraction methods with PSD.
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