Influence of acetonitrile, dimethylsulphoxide and lead on the electro-oxidation of small organic molecules: an on-line mass spectroscopy study

Abstract

The electro-oxidation of HCOOH in 0.05 M H 2SO 4 was investigated in an electrolyte containing Pb 2+ or acetonitrile. The catalytic effect caused by the simultaneous presence of lead and acetonitrile is higher than that of acetonitrile or lead alone. The influence of acetonitrile on the electro-oxidation of formamide and dimethylformamide at a painted Pt electrode in 0.05 M H 2SO 4 was also investigated. At potentials below 0.6 V / RHE the oxidation of formamide is catalysed by the presence of acetonitrile in the electrolyte; however, the electro-oxidation of dimethylformamide is inhibited under these conditions. The electro-oxidation of HCOOH was also investigated in the presence of dimethylsulphoxide (DMSO). It was found that DMSO inhibits the oxidation of formic acid. The addition of Pb 2+ to the DMSO-containing electrolyte is able to compensate for the inhibitory effect of DMSO. Nevertheless, the original catalytic effect of lead is not obtained in the presence of DMSO. In contrast with formic acid, the electro-oxidation of methanol at a painted Pt electrode in an electrolyte containing 0.05 M H 2SO 4 + 0.1 M CH 3OH is inhibited by the presence of acetonitrile. Furthermore, the inhibitory effect of the same concentration of DMSO is stronger than that of acetonitrile.