Researching of microbial electrolysis mechanism of organic rich material containing wastewater for hydrogen production

In this study, hydrogen production via microbial electrolysis of wastewater was carried out on edge plane pyroytic graphite electrode (EPPG) using Shewanella oneidensis MR-1 and Geobacter metallireducens exoeletrogenic bacteria. To determine optimum potential condition of the system, microbial electrolysis was performed with glucose in supporting electrolyte solution as a carbon source at various potential applications (0.5, 0.7 and 1.0 V). The optimum potential was found to be 0.7 V for S. oneidensis MR-1 and 1.0 V for G. metallireducens. Those potentials were used for microbial electrolysis of wastewater samples. Hydrogen evolution mecanism of the bacteria was researched using rotating disc electrode system and cyclic voltammetry technique. The results showed that higher over potential was required for hydrogen evolution on EPPG electrode. However, the presence of bacteria in the solution decreased the activation energy required to ensure hydrogen evolution reaction. Hydrogen evolution efficiency of G. metallireducens was better compared to S. oneidensis MR-1. Current increased while G. metallireducens was present on electrode surface. Therefore, electron transfer between electrode/solution carried out faster. Not only electron transfer but also proton transfer accelarated by increasing cathodic current and hydrogen evolution. These results showed that the mass-transport prosses was more effective with G. metallireducens.