Improved performance of porous bio-anodes in microbial electrolysis cells by enhancing mass and charge transport

To create an efficient MEC high current densities and high coulombic efficiencies are required. The aim of this study was to increase current densities and coulombic efficiencies by influencing mass and charge transport in porous electrodes by: (i) introduction of a forced flow through the anode to see the effect of enhanced mass transport of substrate, buffer and protons inside the porous anode and (ii) the use of different concentrations of buffer solution to study the effect of enhanced proton transport near the biofilm. A combination of both strategies led to a high current density of 16.4 A m−2 and a hydrogen production rate of 5.6 m3 m−3 d−1 at an applied voltage of 1 V. This current density is 228% higher than the current density without forced flow and high buffer concentration. Furthermore the combination of the anode and transport resistance was reduced from 36 mΩm2 to 20 mΩm2. Because of this reduced resistance the coulombic efficiency reached values of over 60% in this continuous system.