Hydrogen production in microbial reverse-electrodialysis electrolysis cells using a substrate without buffer solution

•Using a substrate without buffer solution in MRECs achieved hydrogen production.•Increasing in anolyte HRT and OLR increased cell current with stable anode potential.•Hydrogen production rate was 0.61 m3-H2/m3-Van/d (yield = 0.51 mol-H2/mole-COD).•Efficiencies of Coulombic and COD removal were 41% and 81% (rate: 1.55 g-COD/L/d).

The aim of this work was to use substrate without buffer solution in a microbial reverse-electrodialysis electrolysis cell (MREC) for hydrogen production under continuous flow condition (10 cell pairs of RED stacks, HRT = 5, 7.5, and 15 h). Decreasing in the HRT (increasing in the organic matter) made cell current stable and increased. Hydrogen gas was produced at a rate of 0.61 m3-H2/m3-Van/d in H-MREC, with a COD removal efficiency of 81% (1.55 g/L/d) and a Coulombic efficiency of 41%. This MREC system without buffer solution could successfully produce hydrogen gas at a consistent rate.