Larisa Karpenko-Jereb - Academia.edu (original) (raw)
Uploads
Papers by Larisa Karpenko-Jereb
Knowledge of the correlation between the molecular polyelectrolyte structure of membranes and the... more Knowledge of the correlation between the molecular polyelectrolyte structure of membranes and their transport properties helps to develop new ion-exchange polymers with improved characteristics. This research paper studies the transport properties of two counter-ions, H + and Na + , inside four commercial cationic membranes with experimental methods: three aromatic hydrocarbon polymer membranes CM-1, CMX, MK-40, and one tetrafluoroethylene polymer Nafion analog membrane MF-4SK. Ab initio calculations of the membrane structures with various hydration levels were applied in order to interpret the difference in the transport parameters of counter-ions between aromatic hydrocarbon MK-40 and non-aromatic perfluorinated MF-4SK polymer membranes. The membrane physico-chemical characteristics and the conductivity were experimentally investigated as a function of NaCl and HCl aqueous solution concentration. The conductivity and diffusion coefficients of the counter-ions, as well as volume fractions of 'gel' and 'inter-gel' phases were determined based on the microheterogeneous two-phase model. For the first time, ab initio calculations on membrane models were correlated with experimental findings in order to explain the difference in the mobility of the two counter-ions. The static ab initio study indicates the dissociation of the functional groups and a stronger water connectivity in perfluorinated membrane, providing an explanation for the measured highest diffusion coefficient and molar conductivity of the counter-ions H + and Na + in MF-4SK membrane in comparison to MK-40 membrane.
Colloid journal of the Russian Academy of Sciences, Nov 1, 2016
The known Schroeder paradox, i.e., a difference in the degree of swelling of ion-exchange polymer... more The known Schroeder paradox, i.e., a difference in the degree of swelling of ion-exchange polymers at equilibrium with liquid water and its vapor, has been discussed. It has been noted that there is no paradoxicality in this phenomenon. An example of different "swelling" based on trivial physical considerations has been presented. A simple mechanism has been proposed for increased swelling of an ion-exchange polymer immersed in liquid water, this mechanism being associated with the action of the Maxwell stresses at a polymer/electrolyte interface. The predicted values of the "excess" swelling have been shown to correspond to the data of real experiments.
Measurement of the stationary nucleation rate as a function of supersaturation in reactive precip... more Measurement of the stationary nucleation rate as a function of supersaturation in reactive precipitation requires that nucleation and growth of the crystals to an observable size take place under well-controlled hydrodynamic conditions and at a constant supersaturation. An experimental method was chosen that is based on the measurement of the increase of the particle concentration with the increase of the residence time in a precipitation tube. This method was applied to measure the nucleation rate for the pH shift precipitation of the molecular compound H 4 EDTA. The parameters A and B in the classical nucleation theory equation were derived from the measured nucleation rates. A value of A) (5.7 (1.0) × 10 15 m-3 s-1 was found for the intercept with the ordinate and a value of B) (3.3 (2.0) × 10 2 was found for the slope. The estimated value for parameter A is lower than the theoretical value of A HON) 10 33 m-3 s-1 for homogeneous nucleation. Using the experimentally determined value for B the interfacial energy is found to be γ) 21 (9 mJ m-2 compared to a theoretical value of γ HON) 38 mJ m-2 based on bulk properties. The experimentally obtained values for A and γ indicate heterogeneous nucleation.
Journal of Analytical Chemistry, 2014
Journal of Analytical Chemistry, 2013
International Journal of Hydrogen Energy, 2023
Elsevier eBooks, 2018
Abstract This chapter describes the main components of the polymer electrolyte fuel cell and its ... more Abstract This chapter describes the main components of the polymer electrolyte fuel cell and its role in cell performance. It presents five synthesis routes for the preparation of electrocatalysts, and discusses the influence of nanoparticle formation on the catalytic properties. Regarding the polymer electrolyte membranes, the chapter explains proton transport within membranes based on their structural features. Physicochemical and transport properties characterizing the membranes are described as well. The chapter further highlights the importance of bipolar plates in general, the selection of suitable bipolar plate materials, and different flow-field designs.
International Scientific Conference on Pervaporation, Vapor Permeation and Membrane Distillation, 2013
Journal of Analytical Chemistry, 2014
Knowledge of the correlation between the molecular polyelectrolyte structure of membranes and the... more Knowledge of the correlation between the molecular polyelectrolyte structure of membranes and their transport properties helps to develop new ion-exchange polymers with improved characteristics. This research paper studies the transport properties of two counter-ions, H + and Na + , inside four commercial cationic membranes with experimental methods: three aromatic hydrocarbon polymer membranes CM-1, CMX, MK-40, and one tetrafluoroethylene polymer Nafion analog membrane MF-4SK. Ab initio calculations of the membrane structures with various hydration levels were applied in order to interpret the difference in the transport parameters of counter-ions between aromatic hydrocarbon MK-40 and non-aromatic perfluorinated MF-4SK polymer membranes. The membrane physico-chemical characteristics and the conductivity were experimentally investigated as a function of NaCl and HCl aqueous solution concentration. The conductivity and diffusion coefficients of the counter-ions, as well as volume fractions of 'gel' and 'inter-gel' phases were determined based on the microheterogeneous two-phase model. For the first time, ab initio calculations on membrane models were correlated with experimental findings in order to explain the difference in the mobility of the two counter-ions. The static ab initio study indicates the dissociation of the functional groups and a stronger water connectivity in perfluorinated membrane, providing an explanation for the measured highest diffusion coefficient and molar conductivity of the counter-ions H + and Na + in MF-4SK membrane in comparison to MK-40 membrane.
Colloid journal of the Russian Academy of Sciences, Nov 1, 2016
The known Schroeder paradox, i.e., a difference in the degree of swelling of ion-exchange polymer... more The known Schroeder paradox, i.e., a difference in the degree of swelling of ion-exchange polymers at equilibrium with liquid water and its vapor, has been discussed. It has been noted that there is no paradoxicality in this phenomenon. An example of different "swelling" based on trivial physical considerations has been presented. A simple mechanism has been proposed for increased swelling of an ion-exchange polymer immersed in liquid water, this mechanism being associated with the action of the Maxwell stresses at a polymer/electrolyte interface. The predicted values of the "excess" swelling have been shown to correspond to the data of real experiments.
Measurement of the stationary nucleation rate as a function of supersaturation in reactive precip... more Measurement of the stationary nucleation rate as a function of supersaturation in reactive precipitation requires that nucleation and growth of the crystals to an observable size take place under well-controlled hydrodynamic conditions and at a constant supersaturation. An experimental method was chosen that is based on the measurement of the increase of the particle concentration with the increase of the residence time in a precipitation tube. This method was applied to measure the nucleation rate for the pH shift precipitation of the molecular compound H 4 EDTA. The parameters A and B in the classical nucleation theory equation were derived from the measured nucleation rates. A value of A) (5.7 (1.0) × 10 15 m-3 s-1 was found for the intercept with the ordinate and a value of B) (3.3 (2.0) × 10 2 was found for the slope. The estimated value for parameter A is lower than the theoretical value of A HON) 10 33 m-3 s-1 for homogeneous nucleation. Using the experimentally determined value for B the interfacial energy is found to be γ) 21 (9 mJ m-2 compared to a theoretical value of γ HON) 38 mJ m-2 based on bulk properties. The experimentally obtained values for A and γ indicate heterogeneous nucleation.
Journal of Analytical Chemistry, 2014
Journal of Analytical Chemistry, 2013
International Journal of Hydrogen Energy, 2023
Elsevier eBooks, 2018
Abstract This chapter describes the main components of the polymer electrolyte fuel cell and its ... more Abstract This chapter describes the main components of the polymer electrolyte fuel cell and its role in cell performance. It presents five synthesis routes for the preparation of electrocatalysts, and discusses the influence of nanoparticle formation on the catalytic properties. Regarding the polymer electrolyte membranes, the chapter explains proton transport within membranes based on their structural features. Physicochemical and transport properties characterizing the membranes are described as well. The chapter further highlights the importance of bipolar plates in general, the selection of suitable bipolar plate materials, and different flow-field designs.
International Scientific Conference on Pervaporation, Vapor Permeation and Membrane Distillation, 2013
Journal of Analytical Chemistry, 2014