MICROHYDRATION OF HYDRONIUM ION AND ZÜNDEL ION: A MANY-BODY ANALYSIS APPROACH

Abstract

Studying the solvation of an extra proton is important for understanding the proton transfer mechanism in polymer electrolyte membrane fuel cell. We study the interaction of hydronium ion and Zündel ion with water molecules in their first solvation shell using density functional method. A many-body analysis approach has been used to know the contribution of many-body energies to the binding energy of the hydronium ion–(water)3 and Zündel ion–(water)4 hydrogen bonded complex. It was observed that not only two-body energies but three-body and four-body energies also contribute significantly to the binding energy of the hydronium ion–(water)3 and Zündel ion–(water)4 complexes. The binding energy for the former is -32.14 kcal/mol whereas that for the latter is -48.48 kcal/mol. The percentage contributions of the many-body energies to the binding energies for these complexes are reported. The contribution from the relaxation energy to the binding energy of hydronium ion–(water)3 and Zündel ion–(water)4 complexes is 6% and 4.58%, respectively.