The electrosynthesis of H2O2 via O-2 reduction was feasible employing cheap, unmodified graphite felt on top of carbon cloth as air-diffusion cathode fitted into an undivided filter-press cell. The experiments were performed in a pre-pilot plant with recirculation of 4 dm(3) of 0.05 M Na2SO4 solutions at pH 3.0 upon continuous air feeding to the cathode. The H2O2 electrogeneration occurred within the range -0.30 <= E <= -0.01 V vertical bar SHE, being dependent on the mean linear flow velocity (u), which is related to the mass transport of hydronium ions. Optimum conditions achieved at E = -0.30 V vertical bar SHE and u = 27.4 cm s(-1) yielded 100.4 mg dm(-3) H2O2, with efficiency close to 100% and low energy consumption.