The mechanism by which pyridinium (pyrH+) is reduced at a Pt electrode is a matter of recent controversy. The quasireversible cyclic voltammetric wave observed at -0.58 V vs SCE at a Pt electrode was originally proposed to correspond to reduction of pyrH+ to pyridinyl radical (pyrH•). This mechanistic explanation for the observed electrochemistry seems unlikely in light of recent quantum mechanical calculations that predict a very negative reduction potential (-1.37 V vs SCE) for the formation of pyrH•. Several other mechanisms have been proposed to account for the discrepancy in calculated and observed reduction potentials, including surface adsorption of pyrH•, reduction of pyrH+ by two electrons rather than one, and reduction of the pyrH+ proton to a surface hydride rather than a π-based radical product. This final mechanism, which can be described as inner-sphere reduction of pyrH+ to form a surface hydride, is consistent with experimental observations.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry