Microbial electrolysis cells with polyaniline/multi-walled carbon nanotube-modified biocathodes

• Different PANI/MWCNT composites were prepared and used to modify biocathode in MECs.
• The performance of MECs was improved by the modification.
• 75% wt PANI/MWCNT modified biocathode showed the better capacity on hydrogen generation.
• LVS, SEM, DGGE were determined to figure out the effect of modification on MECs.
• PANI/MWCNT modified biocathode in MECs was first studied to push MECs technology forward.

In this paper, we modified biocathodes with PANI (Polyaniline)/MWCNT (Multi-Walled Carbon Nanotube) composites to improve hydrogen production in single-chamber, membrane-free biocathode MECs. The results showed that the hydrogen production rates increased with an increase in applied voltage. At an applied voltage of 0.9 V, the modified biocathode MECs achieved a hydrogen production rate of 0.67m3m−3d−1, current density of 205 Am−3, COD of 86.8%, coulombic efficiency of 72%, cathodic hydrogen recovery of 42%, and energy efficiency of 81% with respect to the electrical power input. LSV (Linear Sweep Voltammetry) scans, SEM (Scanning Electron Microscopy) images and DGGE (Denaturing Gradient Gel Electrophoresis) demonstrated that hydrogen production is catalyzed by the special biofilm attached on a modified biocathode, and the microorganism species and quantity present were significantly different between the modified biocathode and the non-modified biocathode. In general, the performance of MECs with modified biocathodes was improved in the presence of a higher current density and hydrogen generation rate.