Tailoring Microbial Electrochemical Cells for Production of Hydrogen Peroxide at High Concentrations and Efficiencies

Abstract

A microbial peroxide producing cell (MPPC) for H₂ O₂ production at the cathode was systematically optimized with minimal energy input. First, the stability of H₂ O₂ was evaluated using different catholytes, membranes, and catalyst materials. On the basis of these results, a flat-plate MPPC fed continuously using 200 mm NaCl catholyte at a 4 h hydraulic retention time was designed and operated, producing H₂ O₂ for 18 days. H₂ O₂ concentration of 3.1 g L^-1 H₂ O₂ with 1.1 Wh g^-1 H₂ O₂ power input was achieved in the MPPC. The high H₂ O₂ concentration was a result of the optimum materials selected. The small energy input was largely the result of the 0.5 cm distance between the anode and cathode, which reduced ionic transport losses. However, >50 % of operational overpotentials were due to the 4.5-5 pH unit difference between the anode and cathode chambers. The results demonstrate that a MPPC can continuously produce H₂ O₂ at high concentration by selecting compatible materials and appropriate operating conditions.

Keywords: anode-respiring bacteria; cathodes; electrochemistry; hydrogen peroxide; microbial electrochemical cells.