Electrochemical synthesis of hydrogen peroxide with a three‐dimensional rotating cylinder electrode

BACKGROUND This work analyzes the synthesis of H2O2 from dilute NaOH solutions under 0.1 MPa O2 using a batch reactor with a three-dimensional rotating cylinder electrode. The centrifugal force produces a radial co-current flow of the gas and liquid phases. Thus, good mass transfer conditions are achieved and the O2 reduced to H2O2 is easily replenished in the liquid phase. RESULTS Experiments with a glassy carbon rotating disc electrode identified 0.5 mol L-1 NaOH at 30°C as suitable operating conditions. Galvanostatic experiments with three-dimensional rotating electrodes concluded that the best performance was obtained for a reticulated vitreous carbon structure of 100 ppi, at 40 mA cm-2 of macrokinetic current density and 1000 rpm rotation speed. Long-term experiments showed 79% current efficiency and 8.2 kWh kg-1 specific energy consumption until 6 h of electrolysis, with 8.4 g L-1 H2O2 concentration. However, the current efficiency decreases for longer electrolysis times and consequently the specific energy consumption is increased. Thus after 10 h electrolysis the concentrations were H2O2 10.4 g L-1 and NaOH 1.41 mol L-1. CONCLUSION A reactor having a three-dimensional rotating cylinder electrode with co-current oxygen and liquid flows inside the structure showed promising performance for H2O2 production. © 2013 Society of Chemical Industry