A Fuel-Cell Reactor for the Direct Synthesis of Hydrogen Peroxide Alkaline Solutions from H-2 and O-2

The effects of the type of fuel-cell reactors (undivided or divided by cation-and anion-exchange membranes), alkaline electrolytes (LiOH, NaOH, KOH), vapor-grown carbon fiber (VGCF) cathode components (additives: none, activated carbon, Valcan XC72, Black Pearls 2000, Seast-6, and Ketjen Black), and the flow rates of anolyte (0, 1.5, 12 mLh(-1)) and catholyte (0, 12 mLh(-1)) on the formation of hydrogen peroxide were studied. A divided fuel-cell system, O-2 (g) jVGCF-XC72 cathode vertical bar 2M NaOH catholyte vertical bar cation-exchange membrane (Nafion-117) vertical bar Pt/XC72-VGCF anode vertical bar 2M NaOH anolyte at 12 mLh(-1) flow vertical bar H-2 (g), was effective for the selective formation of hydrogen peroxide, with 130 mAcm(-2), a 2M aqueous solution of H2O2/NaOH, and a current efficiency of 95% at atmospheric pressure and 298 K. The current and formation rate gradually decreased over a long period of time. The cause of the slow decrease in electrocatalytic performance was revealed and the decrease was stopped by a flow of catholyte. Cyclic voltammetry studies at the VGCF-XC72 electrode indicated that fast diffusion of O-2 from the gas phase to the electrode, and quick desorption of hydrogen peroxide from the electrode to the electrolyte were essential for the efficient formation of solutions of H2O2/NaOH.