In order to enhance hydrogen production by facilitated proton transport through a forward osmosis (FO) membrane, the FO membrane was integrated into microbial electrolysis cells (MECs). An improved hydrogen production rate was obtained in the FO-MEC (12.5 +/- 1.84 x 10(-3) m(3) H-2/m(3)/d) compared to that of the cation exchange membrane (CEM) - MEC (4.42 +/- 0.04 x 10(-3) m(3) H-2/m(3)/d) during batch tests (72 h). After an internal resistance analysis, it was confirmed that the enhanced hydrogen production in FO-MEC was attributed to the smaller charge transfer resistance than in the CEM-MEC (90.3 Omega and 133.4 Omega respectively). The calculation of partial internal resistance concluded that the transport resistance can be substantially reduced by replacing a CEM with a FO membrane; decrease of the resistance from 0.069 Omega m(2) to 5.99 x 10(-4) Omega m(2). (C) 2015 Elsevier Ltd. All rights reserved.