Elucidation of Aqueous Solvent-Mediated Hydrogen-Transfer Reactions by ab Initio Molecular Dynamics and Nudged Elastic-Band Studies of NaBH4 Hydrolysis

Abstract

The rational development of aqueous-phase catalysts is limited by a lack of fundamental understanding of the precise role of solvent molecules in the reactions. For deeper insight into these general processes, we carried out a detailed theoretical study of NaBH4 hydrolysis to unravel a plethora of complex reaction pathways. Our study involves no a priori assumptions about individual reactant or product states, which are identified through a combination of ab initio molecular dynamics and nudged elastic-band methods. Snapshots of our computational modeling identify canonical reaction mechanisms whereby the aqueous environment facilitates proton and hydride transfers as well as solvent rearrangements extending across multiple layers of solvation. In addition to providing the most comprehensive computational study of NaBH4 hydrolysis to date, the mechanisms presented herein are relevant for characterizing other reaction processes involving coupled proton-hydride reactions influenced by subtle changes in reaction environments (e.g., those that would be encountered in hydrogen evolution, water oxidation, and CO2 conversion processes). This novel and unbiased quantum chemistry modeling approach shows great promise for computational elucidation of homogeneous phase chemistry.