Research On Fabrication Of Stainless Steel Mesh Based Cathode And The Electricity Generation Of Microbial Fuel Cell

Energy crisis and environmental contamination have been pushing people tosearch for new kinds of sustainable, renewable and clean energy. On the other hand,conventional aerobic wastewater treatment technologies consume huge energy andare not economical, consequently urging us to seek for a substitute technologycapable of reasonable wastewater treatment and energy recycling. Microbial fuelcell（MFC）is able to realize wastewater treatment by utilizing microbes andsimultaneously converse chemical energy from wastewater into cleanbioenergy-electricity, which is considered as a novel wastewater treatmenttechnology with both opportunity and challenge. Currently, the main bottleneck ofMFC is how to further lower the capital cost and how to scale up, which determinesits future industrialization.Aiming at the MFC bottleneck, and taking conventional cubic single-chamberair-cathode MFC as research object, reactors with carbon cloth（CC）and stainlesssteel mesh（SSM）based cathodes were investigated on electricity generation,treatment efficiency, microbial community structure etc.in this article; on the otherhand, MFC cathode was improved using cheap, practical SSM and waterproofbreathable membrane（WBM）and was performance-tested on various aspects,proposing a more reasonable cathode fabrication method in comparison withconventional method. Results and conclusion were showed as follows.Cathodes were fabricated using CC and SSM （mesh No.80） throughconventional method, thus two different types of MFCs were obtained. SSM-MFCcould reach the maximum power density of32.9and31.3W/m3, which were slightlyinferior in comparison with CC-MFC（26.6and24.5W/m3, respectively）, howeverfor treatment efficiency and coulombic efficiency, the performance were similarbetween two MFCs. As454pyrosequencing results illustrated, both anode andcathode microbial community structure were similar between two types of MFCs atphylum and class level. At family level, the main domination populations ofCC-MFC anode were Geobacteraceae（39.5%）and Comamonadaceae（26.0%), anddomination populations of CC-MFC cathode were as well Comamonadaceae（45.6%） and Geobacteraceae （20.4%）. They were identified asexoelectrogens-likely bacteria of similar populations, but the correspondingproportions were different, which could be one of the key factors leading to theelectricity generation divergence; Comamonadaceae（57.7%）and Rhodocyclaceae（14.0%）were main domination populations of CC-MFC cathode while the main domination population of SSM-MFC cathode was Xanthomonadaceae（49.8%）, andthis probably came from the difference of cathode skeleton materials. Amongcathode dominated populations, there might live bacteria influencing the MFCperformance in both good and bad way.Fabricating cathode by using CC as material and eliminating Carbon/PTFEwould slightly decrease power generation by20%（due to increase in air diffusionresistance and reactor internal resistance）, but the layer could be eliminated ifnecessary as the layer fabrication was complicated. Fabricating cathode by usingSSM（mesh No.40,60and80）as skeleton material, WBM as air diffusion layer, andbrushing catalyst on SSM (SSM/M cathode) showed favorable performance（27.0、35.4and36.7W/m3for respectively No.40,60and80SSM）at early operationperiod, but the power generation continuously decreased in long-term operation（e.g.decreasing to6.5W/m3for No.40SSM）. The power generation increased with theSSM mesh number, and with mesh number over60, it could transcended that ofMFC（30.0W/m3and30.5W/m3for CC-MFC and SSM-MFC）obtained usingconventional cathode fabrication method. Fabricating cathode by applying catalyston WBM, we could obtain SSM/Pt on M cathode. It reached the power density of24.7W/m3and could ensure long-term operation stability. Based on SSM/Pt on M,we could obtain Pt on M cathode by removing SSM. This cathode had more simplestructure, and as well showed long-term operation stability. However, its powergeneration was rather awful（7.6W/m3）and the cathode structure was not firmenough for easy scaling up. Overall, SSM/Pt on M cathode was relatively cheaper（about16USD/m2）, more simple（less raw material, fabrication in two steps）andsaved time（consuming less than0.5h and the time almost remained nearly the sameafter scaling up）, which was considered as the most reasonable one. Therefore, weput forward a more feasible and practical air-cathode fabrication method based onSSM and WBM.