Hydrogen production from acetate in a cathode-on-top single-chamber microbial electrolysis cell with a mipor cathode

A cathode-on-top single-chamber microbial electrolysis cell (MEC) was constructed by putting the cathode above the anode. The cathode was made of mipor titanium tube coated with platinum and the anode was graphite granules with exoelectrogens absorbed on its surface. Sodium acetate was used as the substrate. In 24 h batch tests, when the applied voltages increased from 0.2 V to 1.0 V with an interval of 0.1 V, the hydrogen production rates increased from 0.03 L/L/d to 1.58 L/L/d, and the overall hydrogen recoveries increased from 26.03% to 87.73%. The maximum overall energy recovery was 86.78% when the applied voltage was 0.6 V. Meanwhile, hydrogen production was accompanied by evolution of methane, and the main methane producer in this MEC was hydrogenotrophic methanogens. The methane production rate increased with the increase of the hydrogen production rate when the applied voltage was under 0.5 V; however, it maintained approximately 0.04 L/L/d when the applied voltage was above 0.5 V. These results demonstrate that putting the cathode above the anode is able to increase the hydrogen recoveries but also obtain high hydrogen production rates. These results also demonstrate that operating this MEC at a relative higher voltage (>0.6 V) is able to reduce methane production and improve the hydrogen recovery in 24 h batch tests. (C) 2010 Elsevier B.V. All rights reserved.