| 1. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Unusual ion transport behaviour of ethylammonium nitrate mixed with lithium nitrate
- 2021
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Ingår i: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 340
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Tidskriftsartikel (refereegranskat)abstract
- The diffusivity of ions and ionic conductivity of ethylammonium nitrate (EAN) mixed with lithium nitrate (LiNO3) has been carried out as a function of Li-salt concentration and temperature. An unusual behavior of ion diffusivities and ionic conductivities of the mixtures are observed over a range of Li-salt concentration and temperature. The diffusivities of EA+ and Li+, as measured by pulsed-field gradient (PFG) nuclear magnetic resonance (NMR) diffusometry, are found to be comparable in the lower temperature range. An overall decrease in the ion diffusivity is observed with an increase in the concentration of LiNO3. A lower degree of dissociation of ionic complexes in the presence lower concentration of the Li-salt (less than 6 mol. %) resulted in lower ionic conductivity. In the higher concentration range of Li-salt the Li+ diffusivity is monotonously decreased with an increase in the concentration. In the lower concentration range, the Li+ diffusivity exceeded the diffusivity of EA+ cation demonstrating the release of Li+ from the associates. Being enclosed between glass plates, the diffusivities of EA+ and Li+ showed peculiarities similar to the earlier observed results for neat nitrate ILs: accelerated diffusivity of cations and reversible alteration of diffusivities under the influence of strong static magnetic field.
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| 2. |
- Khan, Inayat Ali, et al.
(författare)
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Ion Transport and Electrochemical Properties of Fluorine-Free Lithium-Ion Battery Electrolytes Derived from Biomass
- 2021
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 9:23, s. 7769-7780
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Tidskriftsartikel (refereegranskat)abstract
- Unlike conventional electrolytes, ionic liquid (IL)-based electrolytes offer higher thermal stability, acceptable ionic conductivity, and a higher electrochemical stability window (ESW), which are indispensable for the proper functioning of Li-ion batteries. In this study, fluorine-free electrolytes are prepared by mixing the lithium furan-2-carboxylate [Li(FuA)] salt with the tetra(n-butyl)phosphonium furan-2-carboxylate [(P4444)(FuA)] IL in different molar ratios. The anion of these electrolytes is produced from biomass and agricultural waste on a large scale and, therefore, this study is a step ahead toward the development of renewable electrolytes for batteries. The electrolytes are found to have Tonset higher than 568 K and acceptable ionic conductivities in a wide temperature range. The pulsed field gradient nuclear magnetic resonance (PFG-NMR) analysis has confirmed that the (FuA)− anion diffuses faster than the (P4444)+ cation in the neat (P4444)(FuA) IL; however, the anion diffusion becomes slower than cation diffusion by doping Li salt. The Li+ ion interacts strongly with the carboxylate functionality in the (FuA)− anion and diffuses slower than other ions over the whole studied temperature range. The interaction of the Li+ ion with the carboxylate group is also confirmed by 7Li NMR and Fourier transform infrared (FTIR) spectroscopy. The transference number of the Li+ ion is increased with increasing Li salt concentration. Linear sweep voltammetry (LSV) suggests lithium underpotential deposition and bulk reduction at temperatures above 313 K.
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| 3. |
- Khan, Inayat, et al.
(författare)
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Zinc-Coordination Polymer-Derived Porous Carbon-Supported Stable PtM Electrocatalysts for Methanol Oxidation Reaction
- 2021
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 6:10, s. 6780-6790
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Tidskriftsartikel (refereegranskat)abstract
- Porous carbon (PC) is obtained by carbonizing a zinc-coordination polymer (MOF-5) at 950 °C and PtM (M = Fe, Co, Ni, Cu, Zn) nanoparticles (NPs), which are deposited on PC using the polyol method. Structural and morphological characterizations of the synthesized materials are carried out by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM), and the porosity was determined using a N2 adsorption/desorption technique. The results revealed that PtM NPs are alloyed in the fcc phase and are well dispersed on the surface of PC. The electrochemical results show that PtM/PC 950 catalysts have higher methanol oxidation reaction (MOR) performances than commercial Pt/C (20%) catalysts. After 3000 s of chronoamperometry (CA) test, the MOR performances decreased in the order of Pt1Cu1/PC 950 > Pt1Ni1/PC 950 > Pt1Fe1/PC 950 > Pt1Zn1/PC 950 > Pt1Co1/PC 950. The high MOR activities of the synthesized catalysts are attributed to the effect of M on methanol dissociative chemisorption and improved tolerance of Pt against CO poisoning. The high specific surface area and porosity of the carbon support have an additional effect in boosting the MOR activities. Screening of the first row transition metals (d5+n, n = 1, 2, 3, 4, 5) alloyed with Pt binary catalysts for MOR shows that Pt with d8 (Ni) and d9 (Cu) transition metals, in equivalent atomic ratios, are good anode catalysts for alcohol fuel cells.
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| 4. |
- Munavirov, Bulat, et al.
(författare)
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The effect of anion architecture on the lubrication chemistry of phosphonium orthoborate ionic liquids
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Phosphonium ionic liquids with orthoborate anions have been studied in terms of their interfacial film formation, both physisorbed and sacrificial from chemical breakdown, in sheared contacts of varying harshness. The halogen-free anion architecture was varied through (i) the heteronuclear ring size, (ii) the hybridisation of the constituent atoms, and (iii) the addition of aryl functionalities. Time of Flight-Secondary Ion Mass Spectrometry analysis revealed the extent of sacrificial tribofilm formation allowing the relative stability of the ionic liquids under tribological conditions to be determined and their breakdown mechanisms to be compared to simple thermal decomposition. Overall, ionic liquids outperformed reference oils as lubricants; in some cases, sacrificial films were formed (with anion breakdown a necessary precursor to phosphonium cation decomposition) while in other cases, a protective, self-assembly lubricant layer or hybrid film was formed. The salicylate-based anion was the most chemically stable and decomposed only slightly even under the harshest conditions. It was further found that surface topography influenced the degree of breakdown through enhanced material transport and replenishment. This work thus unveils the relationship between ionic liquid composition and structure, and the ensuing inter- and intra-molecular interactions and chemical stability, and demonstrates the intrinsic tuneability of an ionic liquid lubrication technology.
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| 5. |
- Shimpi, Manishkumar R., et al.
(författare)
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Transition anionic complex in trihexyl(tetradecyl)phosphonium-bis(oxalato)borate ionic liquid – revisited
- 2021
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 23:10, s. 6190-6203
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Tidskriftsartikel (refereegranskat)abstract
- It was found that Li[BOB]·nH2O salts were not readily suitable for the synthesis of high-purity orthoborate-based tetraalkylphosphonium ionic liquids, as exemplified here for trihexyl(tetradecyl)phosphonium bis(oxalato)borate, [P6,6,6,14][BOB]; along with [BOB]-, a metastable transition anionic complex (TAC) of dihydroxy(oxalato)borate with oxalic acid, [B(C2O4)(OH)2·(HOOC-COOH)]-, was also formed and passed into the ionic liquid in the course of the metathesis reaction with trihexyl(tetradecyl)phosphonium chloride. On the contrary, Na[BOB] was found to be a more suitable reagent for the synthesis of this IL, because [BOB]- anions safely passed into the final IL without hydrolysis, when metathesis reactions were performed using aqueous-free media. Since ultra-pure Na[BOB] is not commercially available, in this work, a preparation protocol for ultra-pure (>99%) Na[BOB] was developed: (i) molar ratios of boric and oxalic acids were optimised to minimise boron-containing impurities, (ii) the Na[BOB] product was thoroughly purified by sequential washing of a fine powder product in hot acetonitrile and ethanol and (iii) characterised using powder X-ray diffraction and solid-state 11B MAS NMR spectroscopy. The physico-chemical properties of the prepared boron-impurity-free IL, i.e., its density, viscosity, electric conductivity, glass-transition temperature and thermal stability, were found to be significantly different from those of the previously reported [P6,6,6,14][BOB], containing ca. 45 mol% of TAC, [B(C2O4)(OH)2·(HOOC-COOH)]-. It was found that a high-purity [P6,6,6,14][BOB] prepared in this work has a considerably lower viscosity, a higher viscosity index and a wider electro-chemical window (ECW) compared to those of the sample of [P6,6,6,14][BOB] with ca. 45 mol% of TAC. Interestingly, [B(C2O4)(OH)2·(HOOC-COOH)]- in the latter sample almost completely transformed into [BOB]- anions upon heating of the IL sample at 413 K for 1 hour, as confirmed using both 11B and 13C NMR. Therefore, in this work, apart from a well-optimised synthetic protocol for boron-impurity-free [P6,6,6,14][BOB], implications of boron-containing transition anionic complexes in tetraalkylphosphonium-orthoborate ILs used in different applications were highlighted.
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| 6. |
- Wei, Jiayuan, et al.
(författare)
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Oriented Carbon Fiber Networks by Design from Renewables for Electrochemical Applications
- 2021
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 9:36, s. 12142-12154
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Tidskriftsartikel (refereegranskat)abstract
- With the explosion of global demands for electrified mobility systems and a surge in rural energy transport mechanisms augmented by the scarcity of key metals, carbon by design has become a transformational pathway to fill the gap as an energy material of choice. The development of functional carbon from renewables with outstanding electrostatic double-layer capacitance is still in its infancy, as there is a significant gap in understanding the relationship between the tunable structure and properties of the bioresources both before and after their controlled carbonization. Herein, we report carbon fiber networks (CFNs) with highly controllable intact structure manufactured from four functional lignins originating from different types of processing residues, demonstrating excellent electrochemical efficacies, which makes them promising self-standing electrodes in supercapacitors. This study also underpins the feasibility and importance of preparing CFNs with highly oriented structure, which endows superior specific capacitance and cycle stability compared to the CFNs with randomly oriented fibers. The randomly oriented CFNs reached a specific capacitance value of 456 F g–1 under current densities of 1 A g–1 and a cycle stability of 73.6%, while the CFNs with an orientation factor of 0.87 exhibited significant improvement of the specific capacitance by approximately 15% (529 F g–1) and the cycle stability reached 95% after 10 000 charge–discharge cycles. The high specific capacitance and excellent overall electrochemical properties of the highly oriented CFNs make them a cost-effective and greener material of choice for energy storage devices.
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