| 1. |
- Anikina, E. V., et al.
(författare)
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Influence of Kubas-type interaction of B–Ni codoped graphdiyne with hydrogen molecules on desorption temperature and storage efficiency
- 2020
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Ingår i: Materials Today Energy. - : Elsevier. - 2468-6069. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated functionalized 2D carbon allotrope, graphdiyne (GDY), as a promising hydrogen storage media. Density functional theory with a range of vdW corrections was employed to study Ni decoration of pristine and boron-doped GDY and the interaction of resulting structures with molecular hydrogen. We showed that boron-doped GDY is thermally stable at 300 K, though, its synthesis requires an endothermic reaction. Also, boron doping enhances Ni binding with the graphdiyne by increasing the charge transfer from Ni to GDY. Ni doping drastically influenced hydrogen adsorption energies: they rise from ~70 meV per H2 molecule on pristine GDY to a maximum of 1.29 eV per H2 becoming too high in value for room temperature reversible applications. Boron doping improves the situations: in this case, after Ni decoration desorption temperature estimation is ~300–500 K. Overall, each Ni adatom on B-doped GDY can bind only one H2 molecule within the needed energy range, which gives low hydrogen uptake (~1.2 wt%). However, doping with boron led to the decrease in the value of hydrogen adsorption energy and good desorption temperature estimations, therefore, codoping of metal atoms and boron could be an effective strategy for other transition metals.
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| 2. |
- Asfaw, Habtom Desta, Dr. 1986-, et al.
(författare)
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Facile synthesis of hard carbon microspheres from polyphenols for sodium-ion batteries : insight into local structure and interfacial kinetics
- 2020
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Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Hard carbons are the most promising negative active materials for sodium ion storage. In this work, a simple synthesis approach is proposed to produce hard carbon microspheres (CMSs) (with a mean diameter of ~1.3 μm) from resorcinol-formaldehyde precursors produced via acid-catalyzed polycondensation reaction. Samples prepared at 1200, 1400, and 1500 oC showed different electrochemical behavior in terms of reversible capacity, initial coulombic efficiency (iCE), and the mechanism of sodium ion storage. The specific capacity contributions from the flat voltage profile (<0.1 V) and the sloping voltage region (0.1–1 V) showed strong correlation to the local structure (and carbonization temperature) determined by the interlayer spacing (d002) and the Raman ID/IG ratio of the hard carbons (HCs) and the rate of cycling. Electrochemical tests indicated that the HC synthesized at 1500 oC performed best with an iCE of 85–89% and a reversible capacity of 300–340 mAh g−1 at 10 mA g−1, with the majority of charge stored below 0.1 V. The d002 and the ID/IG ratio for the sample were ~3.7 Å and ~1.27, respectively, parameters indicative of the ideal local structure in HCs required for optimum performance in sodium-ion cells. In addition, galvanostatic tests on three-electrode half-cells cells revealed that sodium metal plating occurred as cycling rates were increased beyond 80 mA g−1 leading to considerably high capacity and poor coulombic efficiency, a point that must be considered in full-cell batteries. Pairing the hard CMS electrodes with Prussian white positive electrode, a proof-of-concept cell could provide a specific capacity of almost 100 mAh g−1 maintained for more than 50 cycles with a nominal voltage of 3 V.
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| 3. |
- Calcagno, Giulio, 1990, et al.
(författare)
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Fast charging negative electrodes based on anatase titanium dioxide beads for highly stable Li-ion capacitors
- 2020
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Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid energy storage systems aim to achieve both high power and energy densities by combining supercapacitor-type and battery-type electrodes in tandem. The challenge is to find sustainable materials as fast charging negative electrodes, which are characterized by high capacity retention. In this study, mesoporous anatase beads are synthetized with tailored morphology to exploit fast surface redox reactions. The TiO2-based electrodes are properly paired with a commercial activated carbon cathode to form a Li-ion capacitor. The titania electrode exhibits high capacity and rate performance. The device shows extremely stable performance with an energy density of 27 mWh g-1 at a specific current of 2.5 A g−1 for 10,000 cycles. The remarkable stability is associated with a gradual shift of the potential during cycling as result of the formation of cubic LiTiO2 on the surface of the beads. This phenomenon renews the interest in using TiO2 as negative electrode for Li-ion capacitors.
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| 4. |
- Castin, N., et al.
(författare)
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The dominant mechanisms for the formation of solute-rich clusters in low-Cu steels under irradiation
- 2020
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Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- The formation of nano-sized, coherent, solute-rich clusters (NSRC) is known to be an important factor causing the degradation of the macroscopic properties of steels under irradiation. The mechanisms driving their formation are still debated. This work focuses on low-Cu reactor pressure vessel (RPV) steels, where solute species are generally not expected to precipitate. We rationalize the processes that take place at the nanometer scale under irradiation, relying on the latest theoretical and experimental evidence on atomic-level diffusion and transport processes. These are compiled in a new model, based on the object kinetic Monte Carlo (OKMC) technique. We evaluate the relevance of the underlying physical assumptions by applying the model to a large variety of irradiation experiments. Our model predictions are compared with new experimental data obtained with atom probe tomography and small angle neutron scattering, complemented with information from the literature. The results of this study reveal that the role of immobilized self-interstitial atoms (SIA) loops dominates the nucleation process of NSRC.
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| 5. |
- Raza, Rizwan, 1980, et al.
(författare)
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Functional ceria-based nanocomposites for advanced low-temperature (300–600 °C) solid oxide fuel cell: A comprehensive review
- 2020
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Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 15
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Forskningsöversikt (refereegranskat)abstract
- There is world tendency to develop SOFC to lower temperatures and two technical routes and approaches are going in parallel. One is to use thin film technology, focussing on reducing the electrolyte thickness on conventional electrolyte, e.g. YSZ (yttria-stabilized zirconia) and SDC (samaria-doped ceria) to reduce the cell resistance i.e. to lower the operational temperatures. Another technique is to develop new materials, e.g. functional nanocomposites. This paper presents a state-of-the-art of nanocomposite electrolytes-based advanced fuel cell technology, i.e. low-temperature (300–600 °C) ceria-based fuel cells, a new scenario for fuel cell R&D with an overview of important aspects and frontier subjects. A typical nanocomposite has a core–shell type structure in nano-scale, in which ceria forms a core and a salt, e.g. carbonate or another oxide develops a shell layer covering the core. The functionality of nanocomposites is determined by the interfaces between the constituent phases, which can lead to super or fast ions transport (H+ and O2−) at interfaces. Ionic conductivities >0.1 S cm−1 already at ~300 °C have been reported. Five major characteristics of nanocomposites have been identified as important to their properties and applications in fuel cells: i) advanced materials design based on non-structure or interfacial properties/mechanisms; ii) dual or hybrid H+ and O2− conduction; iii) interfacial super-ionic conduction; iv) transition from non-functional to functional materials; v) use of interfacial and surface redox agents and reactions. In the fuel cell context, it is refer to these functional nano-composites as NANOCOFC (Nanocomposites for Advanced Fuel Cells) to distinguish them from the traditional SOFCs and to be oriented to a new fuel cell R&D strategy.
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| 6. |
- Younus, H. A., et al.
(författare)
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Engineering of a highly stable metal-organic Co-film for efficient electrocatalytic water oxidation in acidic media
- 2020
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Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 Elsevier Ltd Water oxidation is traditionally performed over IrO2 and RuO2 owing to their high stability at low pH compared to molecular O2 evolution catalysts. The low stability of molecular complexes in acids limits their industrial exploitation as anodes in water-splitting devices, where high current densities and proton conductivity are required. Herein, an existing Co(1,10-phenanthroline)2 complex film is engineered to improve its pH-stability via extra OH substituents on the ligand, i.e. 1,10-phenanthroline-4,7-diol. This novel Co(1,10-phenanthroline-4,7-diol)2 complex film is active for water oxidation at low overpotentials and stable at low pH. Since the calculated water oxidation overpotentials of both complexes are similar, the difference in water oxidation activity is attributed to a smaller charge transfer resistance, which originates from a different anchoring style to the electrode via the OH groups of the ligand. This result is supported by electrochemical impedance measurements. The high pH-stability of the Co(1,10-phenanthroline-4,7-diol)2 film is computationally rationalized by a high crystal formation energy observed in DFT calculations. In summary, an acid-stable and active cobalt-based metal-organic film is reported that competes well with most reported earth-abundant catalysts for water oxidation under similar conditions.
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| 7. |
- Zahra, M., et al.
(författare)
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Tailoring the ions and bandgaps in a novel semi-ionic energy conversion device for electrochemical performance
- 2020
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Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- The new semi-ionic energy conversion (SIEC) device has attracted remarkable attention owing to its clean and environmentally friendly applications. In this device, novel materials and mechanisms have been explored using electronic and ionic conductor materials. The tuning effect of the ions and bandgap has been studied to investigate the structural, optical, and electrochemical performance of the material. Composite materials, gadolinium-doped ceria-cadmium-doped ZnO (GDC-ZnCdO), based on ionic gadolinium-doped ceria (GDC) and semiconductor (ZnCdO) in molar ratios of 1:4, 2:3, 3:2, and 4:1 have been prepared by a wet chemical route. The crystalline structure of the GDC-ZnCdO was studied and found to have cubic and hexagonal wurtzite phases with an average crystallite size of 30–40 nm. The morphology of the prepared composite materials is a homogenous and porous structure. It was found that the addition of GDC increases the transmittance and shows a red shift in the bandgap from 2.70 eV to 2.46 eV. The maximum conductivity of 2.0 S/cm1 was achieved for the sample 4GDC-1ZnCdO at 700°C. Electrochemical impedance spectra and X-ray photoelectron spectroscopy analysis were performed to investigate the electrochemical properties of the prepared semi-ionic composite materials. The SIEC device showed a much better performance than a conventional solid oxide fuel cell. The maximum open-circuit voltage (OCV) of about 1.013 Vand power density of 0.65 W/cm2 were obtained using hydrogen fuel at 600°C, as compared with a conventional fuel cell with 0.72 V and 0.27 W/cm2, respectively. Hence, the results reveal that the ions and bandgap tuning play a crucial role in fuel cell functions. Therefore, it has been determined that the bandgap can be tuned to obtain a better and more stable performance of the SIEC device. This study presents a novel approach to enhance the electrochemical performance with the tailoring of the new semi-ionic materials.
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