Synchronous hydrogen and electricity production by dual-cathodes in a bioelectrochemical system

Abstract

Achieving a self-driven microbial electrolysis cell (MEC) to produce hydrogen is important to its applications but remains challenging. Herein, a dual-cathode bioelectrochemical system (BES) was developed, where one cathode produced electricity energy (Power-cathode) and the other cathode produced hydrogen (H2-cathode). When the applied voltage of the H2-cathode was 0.6 V, the maximum voltage generated by the Power-cathode was 0.47 ± 0.03 V, and the hydrogen rate of the H2-cathode was 0.19 ± 0.003 m3/m3/d. The applied voltage of the H2-cathode was ≤0.4 V, which could be supplied entirely with the power generated by the Power-cathode. Geobacter could accumulate in the anodic biofilm through electric potential differences stimulation. The proportion of electroactive bacteria at the bottom of the anode biofilm was higher than that at the top, while denitrifying bacteria were the opposite. A peak-like distribution of electroactive bacteria in the anodic biofilm and denitrifying bacteria formed a valley-like distribution. Those results have demonstrated a new approach based on dual-cathode BES to produce hydrogen and electricity synchronously, and further proposed a bacterial distribution pattern in anode biofilms. This is of great significance for improving the performance of BES in sustainable wastewater treatment and resource recovery.