The low conversion efficiency of substrate is one of the main bottlenecks in dark fermentation for bio-H-2 production. Herein, an enhanced H-2 yield from corn stalk was achieved by integrating dark fermentation and single chamber microbial electrolysis cells (MECs). In the dark fermentation stage, a H-2 yield of 129.8 mL H-2/g-corn stalk and an average H-2 production rate of 1.73 m(3)/m(3) d were recorded at 20 g/L of corn stalk and initial pH 7.0. The effluent from dark fermentation was diluted and further employed as feedstock to generate H-2 by MECs. A H-2 yield of 257.3 mL H-2/g-corn stalk, an HPR of 3.43 +/- 0.12 m(3)/m(3) d and an energy efficiency of 166 +/- 10% were obtained with the effluent COD of 3995.5 mg/L under 0.8 V applied voltage. During MECs operation stage, about 90 +/- 2% of acetate was converted to H-2 and the corresponding COD removal reached 44 2% in MECs. Overall, the H-2 yield can reach 387.1 mL H-2/g-corn stalk by integrating dark fermentation and MECs, which had nearly tripled as against that of dark fermentation. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.