Immobilization of bacterial cells on carbon-cloth anode using alginate for hydrogen generation in a microbial electrolysis cell

In a microbial electrolysis cell (MEC) that operates in wastewater (WW), the anode can be contaminated by non-exoelectrogenic bacteria, leading to a decrease in the hydrogen evolution reaction (HER) rate. In this study, the electrochemical activity and chemical oxygen demand (COD) removal by an MEC based on Geobacter sulfurreducens (1 OD), which is encapsulated on the anode using alginate and chitosan or only alginate (AC-1 and A-1 bacterial anode, respectively), are compared with a non-immobilized anode. When acetate is used as the carbon source, the current density of the MEC based on the non-immobilized anode is 10.95 A m⁻², 15% higher compared to the immobilized bacterial anodes. When WW is used, the AC-1 bacterial anode yields the highest current density: 11.52 A m⁻² at a potential of 0.2 V, 11% and 29% higher than the A-1 and the non-immobilized anodes, respectively. The AC-1 anode leads to a HER rate of 0.56 m³m⁻³d⁻¹ (at 0.5 V), COD removal of 75%, and a composition of 92% G. sulfurreducens. SEM analysis shows a biofilm covered with a layer of (presumed) alginate. To our knowledge, this is the first study demonstrating an MEC based on an immobilized bacterial anode using alginate.