| 1. |
- Abdurrokhman, Iqbaal, 1991
(författare)
-
Binary mixtures and cationic modification of protic ionic liquids. Local structure and transport properties
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Protic ionic liquids are a subclass of ionic liquids, which in many cases are obtained by mixing an equimolar amount of Brønsted acid and base. Protic ionic liquids possess an exchangeable proton that gives them distinct features, e.g. the potential to conduct protons and the ability to form extended hydrogen bonds, which is different from the case of their aprotic counterparts. The protic ionic liquids considered in this thesis are limited to those based on the imidazolium and triazolium cation, which (compared to aprotic ionic liquids) are less developed and have been investigated to a lesser extent. The work included in this thesis has been devoted to investigate strategies that could possibly promote a fast proton motion. These strategies have primarily consisted in mixing a protic ionic liquid with a molecular solvent or another parented ionic liquid and in modifying the cationic structure by either attaching alkyl chains of different length to the imidazolium cation or synthesizing new protic ionic liquids derived from another heterocyclic ring such as triazole. In both cases, a detailed characterization by means of vibrational spectroscopy could provide valuable information about intermolecular interactions. An important finding from the studies conducted in this thesis is that altering the cation's structure or adding a co-solvent leads to a significant change in chemical and transport properties. This thesis also includes an extensive work devoted to develop a new solvent-free method to synthesize dry and pure protic ionic liquids, in the laboratory scale. An analytical approach to accurately quantify their purity using nuclear magnetic spectroscopy has also been developed. In addition, the ionic conductivity of the investigated protic ionic liquid systems has been evaluated by use of impedance spectroscopy, from room temperature up to 140 °C. The results included in my work indicate that the two investigated strategies can potentially be used, each with its limitations, to develop thermochemically stable proton conducting materials based on protic ionic liquids.
|
|
| 2. |
- Abdurrokhman, Iqbaal, 1991, et al.
(författare)
-
Binary Mixtures of Imidazolium-Based Protic Ionic Liquids. Extended Temperature Range of the Liquid State Keeping High Ionic Conductivities
- 2022
-
Ingår i: Frontiers in Chemistry. - : Frontiers Media SA. - 2296-2646. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- Binary mixtures based on the two protic ionic liquids 1-ethylimidazolium triflate ([C2HIm][TfO]) and 1-ethylimidazolium bis(trifluoromethanesulfonyl)imide ([C2HIm][TFSI]) have been investigated, with focus on phase behavior, ionic conductivity, and intermolecular interactions as a function of composition (χTFSI indicating the mole fraction of the added compound). It is found that on addition of [C2HIm][TFSI] to [C2HIm][TfO], the melting temperature is first decreased (0 (Formula presented.) 0.3) and then suppressed (0.3 (Formula presented.) 0.8) resulting in mixtures with no phase transitions. These mixtures display a wide temperature range of the liquid state and should be interesting for use in devices operating at extreme temperatures. The ionic conductivity does not vary significantly across the composition range analyzed, as evidenced in the comparative Arrhenius plot. The activation energy, Ea, estimated by fitting with the Arrhenius relation in a limited temperature range (between 60 and 140 °C) varies marginally and keeps values between 0.17 and 0.21 eV. These marginal differences can be rationalized by the initially very similar values of the two neat protic ionic liquids. Vibrational spectroscopy, including both Raman and infrared spectroscopies, reveals weakening of the cation–anion interactions for increasing content of [C2HIm][TFSI], which is reflected by the blue shift of the average N-H stretching mode and the red shift of the S-O stretching mode in the TfO anion. These trends correlate with the higher disorder in the mixtures observed by DSC and are evidenced by the decrease and suppression of the melting temperature as the amount of [C2HIm][TFSI] is increased.
|
|
| 3. |
- Abdurrokhman, Iqbaal, 1991, et al.
(författare)
-
Protic Ionic Liquids Based on the Alkyl-Imidazolium Cation: Effect of the Alkyl Chain Length on Structure and Dynamics
- 2019
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 123:18, s. 4044-4054
-
Tidskriftsartikel (refereegranskat)abstract
- Protic ionic liquids are known to form extended hydrogen-bonded networks that can lead to properties different from those encountered in the aprotic analogous liquids, in particular with respect to the structure and transport behavior. In this context, the present paper focuses on a wide series of 1-alkyl-imidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [HC n Im][TFSI], with the alkyl chain length (n) on the imidazolium cation varying from ethyl (n = 2) to dodecyl (n = 12). A combination of several methods, such as vibrational spectroscopy, wide-angle X-ray scattering (WAXS), broadband dielectric spectroscopy, and 1 H NMR spectroscopy, is used to understand the correlation between local cation-anion coordination, nature of nanosegregation, and transport properties. The results indicate the propensity of the -NH site on the cation to form stronger H-bonds with the anion as the alkyl chain length increases. In addition, the position and width of the scattering peak q 1 (or the pre-peak), resolved by WAXS and due to the nanosegregation of the polar from the nonpolar domains, are clearly dependent on the alkyl chain length. However, we find no evidence from pulsed-field gradient NMR of a proton motion decoupled from molecular diffusion, hypothesized to be facilitated by the longer N-H bonds localized in the segregated ionic domains. Finally, for all protic ionic liquids investigated, the ionic conductivity displays a Vogel-Fulcher-Tammann dependence on inverse temperature, with an activation energy E a that also depends on the alkyl chain length, although not strictly linearly.
|
|
| 4. |
- Abdurrokhman, Iqbaal, 1991
(författare)
-
Proton conducting ionic liquids-Binary mixtures and structural modifications
- 2020
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Proton conduction is a phenomenon of fundamental importance for biological and chemical systems, such as in photosynthesis and aerobic respiration. Proton conduction is also key in the proton exchange membrane fuel cell, a clean electrochemical device that converts chemical into electrical energy. The archetypical proton exchange membrane is currently a perfluorinated polymer with pending acidic groups. The fuel cell technology is presently at renewed focus in the commercial sector, and consequently also in the scope of research and development programs. In order to enable the development of more sustainable proton exchange membrane fuel cells, new requirements have been set that for instance target operation at higher temperatures and anhydrous conditions. In this context, protic ionic liquids have been highlighted as interesting next-generation electrolytes with the potential to assist proton conduction. Protic ionic liquids are a subset of ionic liquids, also known as low temperature molten salts, entirely composed of ions and displaying very low vapor pressures. Moreover, a protic ionic liquid has an exchangeable proton and is able to establish extended networks of hydrogen bonds. Understanding the dynamics of this local structures is fundamental to design new protic ionic liquids able to sustain a fast proton motion decoupled from the diffusion of the ionic species. To achieve such a dynamical behavior we have investigated two different approaches, that is i) mixing a protic ionic liquid candidate with a co-solvent (here ethylene glycol) able to participate in the hydrogen bonds and ii) modifying the molecular structure of the cation (here by alkyl chains of length (n) varying from ethyl (n=2) to dodecyl (n=12)) in a series of imidazolium based protic ionic liquids. The local intermolecular inter- actions, the nano-structuration as well as ionic and protonic dynamics have been investigated by suitable techniques that include vibrational spectroscopy, NMR spectroscopy, diffusion NMR, impedance spectroscopy and X-ray scattering.
|
|
| 5. |
- Haque, Mohammad Mazharul, 1984, et al.
(författare)
-
Exploiting low-grade waste heat to produce electricity through supercapacitor containing carbon electrodes and ionic liquid electrolytes
- 2022
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 403
-
Tidskriftsartikel (refereegranskat)abstract
- Low-grade thermal energy harvesting presents great challenges to traditional thermoelectric systems based on the Seebeck effect, the thermogalvanic effect, and the Soret effect due to fixed temperature gradient and low voltage output. In this study, we report an ionic thermoelectric system, essentially a supercapacitor (SC) containing an ionic liquid (IL) electrolyte and activated carbon electrodes, which works on the thermocapacitive effect and does not require any fixed temperature gradient, rather it works in a homogeneously changing temperature. A systematic investigation is carried out on SCs containing two different ILs, 1-Ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl), EMIm TFSI, and 1-Ethyl-3-methylimidazolium acetate, EMIm OAc. A high voltage output of 176 mV is achieved for EMIm TFSI containing SC by exposing just to 60 °C environment. Moreover, a large voltage of 502 mV is recovered from the SC upon subjecting to heat after one electrical charge/discharge cycle. A system containing two SCs in series demonstrates a significant voltage of 947 mV. The observed performance difference between the two ILs is rationalized in terms of the extent of asymmetry in the interfaces of the electrical double layer that essentially originates from different diffusivity of individual ions. The mechanism can be applied to a plethora of ILs to exploit low-grade heat to store electricity without a fixed temperature gradient, opening up the possibility to merge different scientific communities and enrich this rising research field.
|
|
| 6. |
- Maurina Morais, Eduardo, 1989, et al.
(författare)
-
Solvent-free synthesis of protic ionic liquids. Synthesis, characterization and computational studies of triazolium based ionic liquids
- 2022
-
Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322. ; 360
-
Tidskriftsartikel (refereegranskat)abstract
- A series of triazolium and imidazolium based protic ionic liquids were synthesized using a solvent-free method designed to address several limitations encountered with other commonly used methods. Using this method, pure (98–99% m/m) and dry (128–553 ppm of water) protic ionic liquids were synthesized (in a laboratory scale) without the need for purification methods that require heating the ionic liquid, hence avoiding the common issue of thermal decomposition. This method was also designed to allow for the accurate measurement of acid and base, and for the controlled mixing of both compounds, which is essential to avoid producing impure protic ionic liquids with excess of either acid or base. The system is constructed of only glass and chemically resistant polymer (PTFE and PVDF) parts, which avoid other contaminants that can result from unwanted reactions involving the reagents with common laboratory tools (metallic objects, paper, plastic, etc.). This process is described in detail in the paper as well as in a video. The resulting ionic liquids were carefully analyzed by spectroscopic and thermal methods designed to avoid water absorption, which is known to affect their properties. To complement this experimental characterization, computational chemistry tools were used to assess the ionic liquids’ properties, as well as to assign vibrational modes.
|
|
| 7. |
- Yaghini, Negin, 1976, et al.
(författare)
-
Transport properties and intermolecular interactions in binary mixtures based on the protic ionic liquid ethylimidazolium triflate and ethylene glycol
- 2018
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 20:35, s. 22980-22986
-
Tidskriftsartikel (refereegranskat)abstract
- The binary mixture based on the protic ionic liquid (PIL) ethylimidazolium triflate (C2HImTfO) and the diol compound ethylene glycol (EG) has been investigated in the whole composition range from pure PIL to pure EG. At 30 °C the addition of EG increases both the ionic conductivity and the self-diffusivity of the ions. These quantities, however, change at different rates suggesting that the ionicity of the system is composition dependent. This behaviour is explained by means of new intermolecular forces established when a second compound like EG is introduced into the ionic network. More specifically, a complex H-bonded network is formed that involves the -NH group of the cation, the -OH group of EG and the -SO3group of the anion. This configuration may increase the fluidity of the mixture but not necessarily the ionic dissociation. Moreover, diffusion NMR results indicate the occurrence of local proton dynamics, which arise from a proton exchange between the -NH of the cation and the -OH of EG, providing the requisite for a long-range Grotthuss mechanism of proton transport.
|
|
