The second part of the work concerned with mediated electrosynthesis of H2O2 in acidic solutions (pH 3) deals with investigations using divided flow-by fixed bed electrochemical cells operated with co-current three-phase flow (aqueous/organic emulsion and O-2 gas at 0.1 MPa). Graphite felt (GF) and reticulated vitreous carbon (RVC) were evaluated as cathodes at superficial current densities up to 3000 A m(-2). Typically, at current densities above 600 A m(-2) graphite felt yielded higher peroxide concentrations per pass and current efficiencies, most likely due to the almost an order of magnitude higher organic liquid to solid mass transfer capacity for 2-ethyl-9,10-anthraquinone (EtAQ) mediator, that is, 0.13 s(-1) in the case of GF vs 0.015 s(-1) for RVC with 39 ppc (pores per cm). Factorial experiments revealed a positive interaction effect between superficial current density and emulsion load with respect to the current efficiency for H2O2 electrosynthesis. Thus, at the highest investigated superficial current density of 3000 A m(-2), the current efficiency was 84% when the emulsion load was at the highest explored level of 11.7 kg m(-2) s(-1), whilest for the lowest level of emulsion load, 2.8 kg m(-2) s(-1), the current efficiency for H2O2 was 18%. Furthermore, the presence of 1 mM cationic surfactant, tricaprylmethylammonium chloride (CH3(C8H17)(3)N+Cl-, A336), had a positive main effect of about 12% on H2O2 current efficiency and there was also a positive synergistic effect between surfactant and emulsion load, estimated at about 7%. The aqueous to organic phase volume ratio, in the range of 0.9/1 and 3/1, had a statistically insignificant effect on the current efficiency for H2O2 generation. A decrease of the aqueous to organic phase volume ratio from 3 to 0.9 increased the cell voltage from about 6.5 to 7.3 V.