The oxidation of formaldehyde on high overvoltage DSA type electrodes

The electrochemical oxidation of formaldehyde is studied on dimensionally s table anodes prepared by thermal decomposition of precursors (the correspon ding chlorides). The working electrodes used were: Ti/Ir0.3Ti0.7O2, Ti/Ru0. 3Ti0.7O2 and Ti/Ir0.2Ru0.2Ti0.6O2. The electrolyses were performed galvanos tatically in a filter press cell with 0.5 mol L-1 H2SO4 solutions with init ial formaldehyde concentration equal to 100 mmol L-1. The concentration of formaldehyde decreases fast with the electrolysis time, with the ternary an ode (Ir + Ru + Ti) presenting the best performance for this step. The anode containing only Ir, despite presenting the higher superficial charge, is t he one with the lowest electrocatalytic activity. For the formic acid oxida tion step, the presence of iridium in the anode composition does not promot e the process, the anode containing only ruthenium being the most effective for this step.