Hydrogen Production Using "Direct-Starting" Biocathode Microbial Electrolysis Cell and the Analysis of Microbial Communities

In this study, a "direct-starting" procedure was used to activate a single-chamber biocathode microbial electrolysis cell (MEC) and the development of a biocathode was studied through output current curves and cyclic voltammograms. It only took 163 h for a successful start-up, and a current density of 14.75 A/m² was obtained. In the formal hydrogen-production stage, it was found that the biocathode MEC was comparable with the Pt/C cathode MEC in terms of current density and energy efficiency, and the hydrogen recovery, cathodic hydrogen recovery, and hydrogen production rate of the biocathode MEC were 71.22% ± 8.98%, 79.42% ± 5.94%, and 0.428 ± 0.054 m³ H₂/m³ · days, respectively, which were slightly higher than those obtained with the Pt/C cathode MEC. Besides, under the effect of applied voltage, the microbial populations in the anodophilic biofilm of MEC (MECan) and the cathodophilic biofilm of MEC (MECca) were less diverse than those of the original aerobic activated sludge (AAS) and the anodophilic biofilm of MEC (MECan). Furthermore, the microbial community structures evidently differed between MECan/MECca and AAS/MFC.