Galvanostatic oxidation of formaldehyde-methanol solutions on Ti/Ru0.3Ti0.7O2 electrodes using a filter-press cell

The galvanostatic oxidation of methanol-containing formaldehyde solutions, under conditions of simultaneous oxygen evolution, in 0.5 M H₂SO₄ acid was studied using a Ti/Ru_0.3Ti_0.7O₂ dimensionally stable anode (DSA^®), in a filter-press cell. The reaction products detected were HCOOH, CO₂ and CO₃ ^2–. The CO₃ ^2– species is formed from the oxidation of HCOOH and subsequently decomposes in solution to CO₂. Conversely CO₂ is also formed electrochemically from the electrooxidation of formaldehyde and methanol. A mechanism, which considers the active and non-active nature of the electrode, is suggested. First-order kinetics, with respect to the variation of formaldehyde and methanol, are displayed and two linear regions observed. This is interpreted as being due to the presence of the reaction products of oxidation inhibiting the oxidation of formaldehyde at the electrode surface. Further, a mechanism is proposed considering the species present in solution.