| 1. |
- Barthwal, M., et al.
(författare)
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Effect of Nanomaterial Inclusion in Phase Change Materials for Improving the Thermal Performance of Heat Storage : A Review
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:8, s. 7462-7480
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Tidskriftsartikel (refereegranskat)abstract
- Dispersion of nanoparticles is one of the potential solutions to improve the thermophysical properties of phase change (or transition) materials (PCMs) and enhance the performance of latent thermal energy storage (LTES) systems. The PCM ought to have a high latent heat of fusion, and zero or negligible coefficient of thermal expansion. A good PCM should have melting and solidification compatibility with negligible or zero subcooling, and it should not react with the common chemical reagents. The present known PCMs possess low thermal conductivity that results into a longer solidification and melting time of PCMs. In the past two decades, researchers have reported improved thermal conductivity and heat-storing capacity of PCMs employing graphite nanoparticles/fibers, carbon nanotubes/fibers, metal, and metal oxide nanoparticles. This work reviews the reported experimental and numerical studies describing the consequences of nanoparticle inclusions of various shapes and sizes on the thermal properties of the PCMs. This review attempts to make a consolidated database of the studies related to nanoadditive inclusion into PCMs for various applications. Graphene dispersed into PCM has resulted into 14 times thermal conductivity enhancement. As far as metal oxide nanoparticles are concerned, TiO2 and Al2O3 nanoparticles outperformed others. The compatibility between the nanoadditive and PCM is necessary to tailor favorable thermal properties. This work reviews numerous studies of different nanoparticle-PCM duos. © 2021 American Chemical Society.
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| 2. |
- Cavallo, Carmen, 1986, et al.
(författare)
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Effect of the Niobium Doping Concentration on the Charge Storage Mechanism of Mesoporous Anatase Beads as an Anode for High-Rate Li-Ion Batteries
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:1, s. 215-225
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Tidskriftsartikel (refereegranskat)abstract
- A promising strategy to improve the rate performance of Li-ion batteries is to enhance and facilitate the insertion of Li ions into nanostructured oxides like TiO2. In this work, we present a systematic study of pentavalent-doped anatase TiO2 materials for third-generation high-rate Li-ion batteries. Mesoporous niobium-doped anatase beads (Nb-doped TiO2) with different Nb5+ doping (n-type) concentrations (0.1, 1.0, and 10% at.) were synthesized via an improved template approach followed by hydrothermal treatment. The formation of intrinsic n-type defects and oxygen vacancies under RT conditions gives rise to a metallic-type conduction due to a shift of the Fermi energy level. The increase in the metallic character, confirmed by electrochemical impedance spectroscopy, enhances the performance of the anatase bead electrodes in terms of rate capability and provides higher capacities both at low and fast charging rates. The experimental data were supported by density functional theory (DFT) calculations showing how a different n-type doping can be correlated to the same electrochemical effect on the final device. The Nb-doped TiO2 electrode materials exhibit an improved cycling stability at all the doping concentrations by overcoming the capacity fade shown in the case of pure TiO2 beads. The 0.1% Nb-doped TiO2-based electrodes exhibit the highest reversible capacities of 180 mAh g-1 at 1C (330 mA g-1) after 500 cycles and 110 mAh g-1 at 10C (3300 mA g-1) after 1000 cycles. Our experimental and computational results highlight the possibility of using n-type doped TiO2 materials as anodes in high-rate Li-ion batteries.
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| 3. |
- Chen, Xi, et al.
(författare)
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2D Silicon-Germanium-Layered Materials as Anodes for Li-Ion Batteries
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:11, s. 12552 -12561
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Tidskriftsartikel (refereegranskat)abstract
- To address the volume changes of Si-based and Ge-based anode materials during lithiation and delithiation, two-dimensional (2D) composites like siloxene and germanane have recently been developed. These 2D materials can insert alkali cations without an alloying reaction, thereby limiting the associated volume expansion. While Si has a high theoretical capacity and low cost, its electrical conductivity is low; on the other hand, Ge provides a higher electronic conductivity but at a higher cost. Therefore, we propose a series of 2D Si-Ge alloys, that is, Si1-xGex with 0.1 < x < 0.9, referred to as siliganes, with reasonable cost and encouraging electrochemical performance. The layered siliganes were obtained by fully deintercalating Ca cations from the Ca(Si1-xGex)2 parent phases and used as Li-ion battery (LIB) anodes. XRD, SEM, Raman spectroscopy, and infrared spectroscopy were used to characterize the materials and identify the mechanisms occurring during cycling in LIBs. Siligane_Si0.9Ge0.1 was identified as the best candidate; at a current density of 0.05 A g-1, after 10 cycles, it showed a reversible capacity of 1325 mA h g-1, with high capacity retention and coulombic efficiency.
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| 4. |
- Danyliv, Olesia, et al.
(författare)
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Self-Standing, Robust Membranes Made of Cellulose Nanocrystals (CNCs) and a Protic Ionic Liquid : Toward Sustainable Electrolytes for Fuel Cells
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society. - 2574-0962. ; 4:7, s. 6474-6485
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Tidskriftsartikel (refereegranskat)abstract
- Energy-conversion devices based on the phenomenon of proton conduction, for example, polymer electrolyte membrane fuel cells (PEMFCs), require low cost and sustainable electrolytes with high ionic conductivity and good mechanical properties under anhydrous conditions and at temperatures up to 150 °C. Biopolymers possess an intrinsic thermomechanical stability but an insufficient proton conductivity in the dry state, which however may be imparted by a protic ionic liquid (PIL). This work presents the preparation and properties of composite membranes made of cellulose nanocrystals (CNCs) and a PIL. The membranes are thermally stable and display an ionic conductivity within the range 10-4-10-3 S/cm for temperatures between 120 and 160 °C. Moreover, the analysis of the biopolymer's apparent dimensions at nanoscale reveals a dependence of the CNCs' defects, twisting, and aggregation in the presence of the PIL. Preliminary tests using a simple fuel cell setup demonstrate a response of the membranes to the inlet of H2 gas, with a generation of electrical current. These findings provide a solid groundwork for further development and future studies of biopolymer/PIL electrolytes for energy applications. © 2021 The Authors.
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| 5. |
- Deshpande, Swapnil S., et al.
(författare)
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Carbon Nitride Monolayers as Efficient Immobilizers toward Lithium Selenides : Potential Applications in Lithium-Selenium Batteries
- 2021
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Ingår i: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 4:4, s. 3891-3904
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Tidskriftsartikel (refereegranskat)abstract
- The low cost, high energy density, and nontoxic nature have made lithium-selenium batteries (LiSeBs) a promising option for large-scale energy storage applications. However, the issue of capacity loss during consecutive charge/discharge cycles has put a serious question mark on the commercialization of LiSeBs. In a quest to suppress the issue of capacity loss due to the dissolution of active lithium polyselenides (Li2Sen, n = 1-8) into the electrolyte, the so-called shuttle effect, we have employed first-principles density functional theory calculations to study the anchoring properties of two carbon nitrides monolayers, namely, nitrogenated holey graphene (C2N) and carbon nitride (C3N). We find that the presence of nitrogen (N) atoms, in both C2N and C3N, enable them to bind Li2Sen clusters stronger than that of graphene. We further discover that the anchoring properties of C2N (-2.03 to -3.82 eV) are stronger than that of C3N (-1.21 to -1.30 eV) due to higher concentrations of N atoms and relatively bigger pore size in the former than the later. In addition to the appropriate bindings, improved conductivities upon the adsorption Li2Sen further reinforce the promise of C2N and C3N as potential anchoring materials for LiSeBs. We believe that our computational results would pave the way toward the experimental synthesis of efficient anchoring materials based on the studied systems.
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| 6. |
- Dürr, Robin N., et al.
(författare)
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Robust and Efficient Screen-Printed Molecular Anodes with Anchored Water Oxidation Catalysts
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:10, s. 10534-10541
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present the preparation and performance of screen-printed anodes for electrochemical water splitting in neutral media. With the combination of printed electrodes and molecular water oxidation catalysts, we successfully take advantage of a low-cost and up-scalable fabrication method of graphitic electrodes with the outstanding catalytic activity and stability of oligomeric ruthenium-based molecular water oxidation catalysts, offering a promising electroanode for water oxidation applications.
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| 7. |
- Gimpel, Thomas, et al.
(författare)
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Electrochemical Carbon Dioxide Reduction on Femtosecond Laser-Processed Copper Electrodes : Effect on the Liquid Products by Structuring and Doping
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:6, s. 5927-5934
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Tidskriftsartikel (refereegranskat)abstract
- A femtosecond laser process is presented increasing the surface area of copper electrocatalysts for an electrochemical CO2 reduction reaction (CO2RR). The laser treatment allows us to tune the surface morphology and the chemical composition of the copper electrocatalysts. This tunability is used to correlate the role of the surface area and catalyst dopants with the selectivity of the CO2RR. The liquid products of the CO2RR are monitored through ex situ nuclear magnetic resonance spectroscopy. The products’ distribution shows that the electrode surface area plays a key role in the electrochemical conversion of CO2 into multicarbon liquid products. We show that sulfur dopants boost the production of formate. Remarkably, by co-doping sulfur and fluoride, we show that the chalcogenide dopant counteracts the known boosting effect of fluoride to convert CO2 into multicarbon products. Oxygen doping in the range of 2–19 atom % does not significantly affect the distribution of liquid products from CO2 electroreduction. In a broad perspective, this work highlights the potential of the femtosecond laser process to fine-tune surfaces to produce photo- and electrocatalyst materials.
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| 8. |
- Gradzka-Kurzaj, Iwona, et al.
(författare)
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Molecular Water Oxidation Catalysis : Characterization of Subnanosecond Processes and Ruthenium "Green Dimer" Formation
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:3, s. 2440-2450
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Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized photoelectrochemical cells were prepared with popular ruthenium sensitizer (RuP) and ruthenium catalyst (RuCAT) coadsorbed on mesoporous titania. The cells were studied in 0.1 M Na2SO4(aq) by spectroscopic methods, including femtosecond transient absorption spectroscopy. The formation of RuCAT dimer can be observed by the naked eye due to the change of color from dark-red to green. The dimer displays a characteristic absorption feature with lambda(max) approximate to 670-680 nm and its formation was found to be accelerated upon irradiation. Electron injection from RuP into titania occurs partially from the excited singlet state decaying on the ultrafast time scale (<0.2 ps) and partially from the triplet state with a time constant of several tens of ps. The decay of the excited RuCAT dimer takes place with a main component of about 1 ps. The quenching of the oxidized RuP by electron transfer from RuCAT is observed with a time constant 150-200 ps and is independent of the excitation fluence. This fast first step of catalyst oxidation further explains the chronoamperometry data recorded for photoanodes made of coadsorbed RuP and RuCAT. Finally, RuCAT in solution shows a remarkable short lifetime of the excited state, with a longest component of about 20 ps.
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| 9. |
- Hultqvist, Adam, et al.
(författare)
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SnOx Atomic Layer Deposition on Bare Perovskite-An Investigation of Initial Growth Dynamics, Interface Chemistry, and Solar Cell Performance
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:1, s. 510-522
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Tidskriftsartikel (refereegranskat)abstract
- High-end organic-inorganic lead halide perovskite semitransparent p-i-n solar cells for tandem applications use a phenyl-C-61-butyric acid methyl ester (PCBM)/atomic layer deposition (ALD)-SnOx electron transport layer stack. Omitting the PCBM would be preferred for manufacturing, but has in previous studies on (FA,MA)Pb(Br,I)(3) and (Cs,FA)Pb(Br,I)(3) and in this study on Cs(0)(.0)(5)FA(0.79)MA(0.16)PbBr(0.51)I(2.49) (perovskite) led to poor solar cell performance because of a bias-dependent light-generated current. A direct ALD-SnOx exposure was therefore suggested to form a nonideal perovskite/SnOx interface that acts as a transport barrier for the light-generated current. To further investigate the interface formation during the initial ALD SnOx growth on the perovskite, the mass dynamics of monitor crystals coated by partial p-i-n solar cell stacks were recorded in situ prior to and during the ALD using a quartz crystal microbalance. Two major finds were made. A mass loss was observed prior to ALD for growth temperatures above 60 degrees C, suggesting the decomposition of the perovskite. In addition, a mostly irreversible mass gain was observed during the first exposure to the Sn precursor tetrakis(dimethylamino)tin(IV) that is independent of growth temperature and that disrupts the mass gain of the following 20-50 ALD cycles. The chemical environments of the buried interface were analyzed by soft and hard X-ray photoelectron spectroscopy for a sample with 50 ALD cycles of SnOx on the perovskite. Although measurements on the perovskite bulk below and the SnOx film above did not show chemical changes, additional chemical states for Pb, Br, and N as well as a decrease in the amount of I were observed in the interfacial region. From the analysis, these states and not the heating of the perovskite were concluded to be the cause of the barrier. This strongly suggests that the detrimental effects can be avoided by controlling the interfacial design.
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| 10. |
- Jain, Preeti, et al.
(författare)
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Nonhalogenated Surface-Active Ionic Liquid as an Electrolyte for Supercapacitors
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:8, s. 7775-7785
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Tidskriftsartikel (refereegranskat)abstract
- We report a nonhalogenated surface-active ionic liquid (SAIL) that consists of the surface-active anion 2-ethylhexyl sulfate and the tetraoctylammonium cation ([N8,8,8,8][EHS]). We explored the thermal and electrochemical properties, i.e., degradation, melting and crystallization temperatures, ionic conductivity, and electrochemical potential window of neat SAIL and its binary mixture with acetonitrile. This SAIL was tested as an electrolyte in a multiwalled carbon nanotube (MWCNT)-based supercapacitor at various temperatures from 298 to 373 K. In addition, we also tested the binary mixture of SAIL with acetonitrile as an electrolyte at lower temperatures (253–298 K). The electrochemical performance of SAIL and the SAIL/acetonitrile binary mixture as a function of temperature was compared with that of a standard electrolyte, an aqueous solution of 6 M KOH, in the same MWCNT-based supercapacitor. The solution resistance (Rs), charge transfer resistance (Rct), and equivalent series resistance (ESR) decreased with an increase in temperature for all SAIL-based electrolytes. We found that the supercapacitor cell with SAIL as an electrolyte has a high specific capacitance (Celec in F g–1), a high energy density (E in Wh kg–1), and a high power density (in W kg–1) compared to those for the binary mixture of SAIL with acetonitrile and for the 6 M KOH aqueous electrolytes, particularly at elevated temperatures. For the SAIL/MWCNT-based supercapacitor, Celec increased from 75 F g–1 at 298 K to 169 F g–1 at 373 K, whereas the energy density increased from 42 Wh kg–1 (at 298 K) to 94 Wh kg–1 (at 373 K) and the power density increased from 75 kW kg–1 (at 298 K) to 169 kW kg–1 (at 373 K) at a scan rate of 2 mV s–1 (potential window = 4 V). This study reveals that SAIL can potentially be used as an electrolyte for high-temperature electrochemical applications for energy storage devices.
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