THE ELECTROOXIDATION OF FORMIC-ACID, FORMAMIDE AND DIMETHYLFORMAMIDE IN AQUEOUS ACID-SOLUTION - A COMPARATIVE-STUDY USING ONLINE MS

The electro-oxidation of formic acid and its derivatives-formamide and dimethylformamide-has been studied at a porous platinum electrode in 0.05 M H2SO4 with special attention to common features of their electrochemical behaviour. It is shown that the contribution of bulk reactions to the electro-oxidation decreases from formic acid towards dimethylformamide, where only adsorbate processes can be observed. All compounds can be oxidized to CO2. As expected, formamide and dimethylformamide produce anodically also nitrogen oxides above 1.2 V. Furthermore, formamide shows evidence for another product being possibly formed in an anodic dehydrogenation. In contrast, these compounds show a high degree of commonality during potentiodynamic oxidation of the adsorbate without organic species in solution forming a peak at 0.7 V vs. rhe in current and mass signal for CO2. In the case of dimethylformamide, a small broad peak appears additionally between 1.0 and 1.4 V vs. rhe in the CO2 signal. This additional peak can be probably attributed to the influence of the methyl groups of dimethylformamide. Adsorbed formamide and dimethylformamide are evolving also nitrogen oxides above 1.2 V vs. rhe. A comparison of the electrochemical behaviour of formic acid with its derivatives allows a deeper understanding of the formic acid oxidation itself.