In Situ Generated Platinum Catalyst for Methanol Oxidation via Electrochemical Oxidation of Bis(trifluoromethylsulfonyl)imide Anion in Ionic Liquids at Anaerobic Condition.

Abstract

The bis(trifluoromethylsulfonyl)imide anion is widely used as an ionic liquid anion due to its electrochemical stability and wide electrochemical potential window at aerobic conditions. Here we report an innovative strategy by directly oxidizing bis(trifluoromethylsulfonyl)imide anion to form a radical electrocatalyst on platinum electrode at anaerobic condition. The in situ generated radical catalyst was shown to catalytically and selectively promote the electrooxidation of methanol to form methoxyl radical, in which the formation potential was drastically decreased with the existence of bis(trifluoromethylsulfonyl)imide radical. The electrochemically generated radical catalyst not only facilitates the oxidation of methanol but also provides good selectivity. The unique double layer structure of the 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Bmpy][NTf2]) likely excludes the diffusion of larger molar mass molecules onto the electrode surface and enables the highly selective methanol oxidation at this IL-electrode interface. Cyclic voltammetry (CV) experiments were used to systematically characterize the details of the electrochemical processes with and without methanol in several other ILs, and a mechanism of the chemical and redox processes was proposed. This study provides a promising new approach for utilizing the unique properties of ionic liquids not only as solvents and electrolytes but also as the medium for in situ generation of electrocatalysts to promote methanol redox reactions for practical applications.