Theoretical Studies on the Polymer-Ion Interaction and the Solvent Effects in the PBI-based Systems

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Brela, Artur Michalak Department of Theoretical

1 Theoretical Studies on the Polymer-Ion Interaction and the Solvent Effects in the PBI-based Systems Mateusz Brela, Artur Michalak Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, Kraków, Poland

2 A Pratt & Whitney alkali fuel cell being assembled for an Apollo spacecraft, 1964 Alkaline Fuel Cells

3 Schematic of a PEM and Alkaline fuel cell

4 PBI-based systems

5 Computational details Ab initio Density Functional Theory (DFT ); ADF 2013 program; Becke-Perdew exchange correlation functional, TZP basis set; Ab initio Molecular Dynamics (DFT-based; CP2K program) Analysis of the electronic structure with Natural Orbitals for Chemical Valence (ETS-NOCV) Analysis of the charge distribution with Molecular Electrostatic Potenial

6 H-PBI

7 H-PBI 116 atoms 218 atoms

8 H-PBI Me-PBI Me-O-PBI Me-PBI-OPO

9 H-PBI

10 Interactions with anions Trimer Me-PBI I -

11 ETS-NOCV method for bond analysis E ( +/- ) + - -

12 ETS-NOCV method for bond analysis E ( + )

13 ETS-NOCV method for bond analysis - - E ( - ) - -

14 ETS-NOCV method for bond analysis DE ( +/- ) = E ( +/- ) [ E ( + ) - E (- ) ]

15 ETS-NOCV method for bond analysis In ADF program, since version M.Mitoraj, A.Michalak, J.Mol.Model. 2007, 13, A.Michalak, M.Mitoraj, T. Ziegler, J. Phys. Chem. A, 2008, M.Mitoraj, A. Michalak, T. Ziegler J. Chem. Theory Comput., 2009, 5,

16 D E interaction [kcal/mol] Interactions with anions

17 D E interaction [kcal/mol] Interactions with anions Hofmeister series (lyotropic series)

18 Me-PBI: Interactions with anions (ETS-NOCV) DE orb covalent" ionic -250 DE elstat +DE Pauli -300

19 Water uptake, solvation Me-O-PBI

20 Me-O-PBI Water uptake, solvation Experimental data for water uptake: HCO 3- > CO 3 2- > Cl - > I -

21 Solvation of free ions Cl - > HCO 3 - > I - does not explain the water-uptake data our results: literature results: ETS Cluster cycle* Monomer cycle Smith: Warshel: ΔE P-18H2O COSMO ΔG solv (A) ΔG solv (A) Exp calc exp calc - Cl ,29-186, HCO ,21-183, I ,39-170,

22 Solvation of free ions Cl - > HCO 3 - > I - does not explain the water-uptake data our results: literature results: ETS Cluster cycle* Monomer cycle Smith: Warshel: ΔE P-18H2O COSMO ΔG solv (A) ΔG solv (A) Exp calc exp calc - Cl ,29-186, HCO ,21-183, I ,39-170,

23 Modeling solvent effects in theoretical calculations Explicit solvation M

24 Modeling solvent effects in theoretical calculations Explicit solvation M

25 Continuum models (implicit solvation) M e

26 Continuum models + explicit solvation M e

27 Continuum models + explicit solvation M e

Thermodynamic cycles Continuum models + explicit solvation ΔG sol P 6+ X - 6 + ΔG sol (H 2 O) n = ΔG bind + ΔG sol P 6+ X - 6 H 2 O n RTln H 2 O /n ΔG sol P 6+

28 Thermodynamic cycles Continuum models + explicit solvation ΔG sol P 6+ X ΔG sol (H 2 O) n = ΔG bind + ΔG sol P 6+ X - 6 H 2 O n RTln H 2 O /n ΔG sol P 6+ X - 6 = ΔG bind + ΔG sol P 6+ X - 6 H 2 O n RTln H 2 O /n ΔG sol (H 2 O) n Bryantsev, V. S.; Diallo, M. S.; Goddard III, W. A. J. Phys. Chem. B 2008, 112, 9709.

29 Me-O-PBI (Cl - ) explicit solvation: 18 water molecules included in the model (or 21, 24) implicit solvation: COSMO continuum model marge: Thermodynamic cluster Me-O-PBI (HCO 3- ) Me-O-PBI (I - )

30 Me-O-PBI P Implicit (COSMO) Explicit (ETS) Thermodynamic Cycle ΔG solv (P) ΔE P-18H2O ΔG solv (P) Me-O-PBI Cl Me-O-PBI HCO Me-O-PBI I

31 Me-O-PBI P Implicit (COSMO) Explicit (ETS) Thermodynamic Cycle ΔG solv (P) ΔE P-18H2O ΔG solv (P) Me-O-PBI Cl Me-O-PBI HCO Me-O-PBI I

32 Me-O-PBI P Implicit (COSMO) Explicit (ETS) Thermodynamic Cycle ΔG solv (P) ΔE P-18H2O ΔG solv (P) Me-O-PBI Cl Me-O-PBI HCO Me-O-PBI I

33 Me-O-PBI P Implicit (COSMO) Explicit (ETS) Thermodynamic Cycle ΔG solv (P) ΔE P-18H2O ΔG solv (P) Me-O-PBI Cl Me-O-PBI HCO Me-O-PBI I HCO 3- > Cl - > I -

34 Me-O-PBI P Implicit (COSMO) Explicit (ETS) Thermodynamic Cycle ΔG solv (P) ΔE P-18H2O ΔG solv (P) Me-O-PBI Cl Me-O-PBI HCO Me-O-PBI I HCO 3- > Cl - > I - Why?

35 Ion binding energy Me-O-PBI ΔE interaction ΔE dist +ΔE elstat + ΔE Pauli ΔE orb Me-O-PBI Cl Me-O-PBI HCO Me-O-PBI I non-covalent covalent lowest DE orb : lowest charge transfer ion polymer

36 lowest DE orb : lowest charge transfer ion polymer resulting in the highest charge separation

37 Main Conclusion The increased solvation energy observed for the system with bicarbonate ions (compared to the polymer interacting with iodide and chloride ions), results from the increased electrostatic interaction with the solvent, which primarily originates from the increased charge separation observed for this system. More details: Dirk Henkensmeier, Hyeongrae Cho, Mateusz Brela, Artur Michalak, Alexander Dyck, Wiebke Germer, Ngoc My Hanh Duong, Jong Hyun Jang, Hyoung-Juhn Kim, Nam-Suk Woo, Tae-Hoon Lim; Anion conducting polymers based on ether linked polybenzimidazole (PBI-OO); International Journal of Hydrogen Energy, 2014, 39 (6), pp Wiebke Germer, Janine Leppin, Carolina Nunes Kirchner, Hyeongrae Cho, Hyoung-Juhn Kim, Dirk Henkensmeier, Kwan-Young Lee, Mateusz Brela, Artur Michalak and Alexander Dyck, Phase Separated Methylated Polybenzimidazole (O-PBI) Based Anion Exchange Membranes, Macromolecular Materials and Engineering, 2015,

38 Thank you very much

39 PBI 6+ +6Cl H 2 O

ETS NOCV description of σ hole bonding

ETS NOCV description of σ hole bonding an insight based on the natural orbitals for chemical valence (NOCV) combined with extended transition state method (ETS) Karol Dyduch, Mariusz Mitoraj, Artur Michalak