Computational studies of proton transfer in phosphonic acid molecules.

摘要

The limitations of conventional Nafion-type sulfonic acid based membrane materials demand the search for other alternative materials which can function as the electrolyte in fuel cells operated at higher temperatures and without humidification. Protogenic groups such as phosphonic acids have recently been proposed as promising separator materials due to their extraordinary amphotericity, i.e., the capability of functioning as both proton donor and proton acceptor. Specifically, the neighboring chemical groups (i.e., alkyl, aryl and fluorinated alkyl groups) attached to the phosphonic acid molecules have a fundamental effect on proton transfer as well as hydrogen bonding. Thus, ab initio calculations were undertaken to understand mechanistic information concerning proton transfer in phosphonic acid functionalized molecules as well as the energetics correlated to this process. The strength of the binding of water was also investigated in both monohydrated phosphonic acids and the corresponding anhydrides. Finally, the profile for proton transfer in the anhydrides was quantified and described.