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

Abstract

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.