Research On The Electrode Design In Benthic Microbial Fuel Cell And Its Catalysis To The Marine Sediment Degradation

Currently, the energy shortage and environmental pollution are two major problems for all mankind. The new pollution-free energy plays a vital role in the further development of society. Benthonic microbial fuel cell (BMFC) is a special kind of non-polluting energy technology. The metabolism of bacteria reduces the organic and inorganic matter in the sediments, while produces current. Thus, BMFC has a promising potential application in the low-power remote-sea monitoring instrument. However, the output power of BMFC is still relatively low, which greatly limits its wider application. In this work, we designed the electrode shape and added the modification reagents for improving the BMFC output power.First, we studied the effect of the electrode shape on the performance of BMFC. We designed the netlike, flat slab, dendritic, and columned anodes, and forest-like and disc-shaped cathodes, assembled them into batteries, and had a group-comparative test. The results show that the netlike and dendritic anodes undergo smaller diffusion resistance, resulting in higher power density and stronger limiting diffusion current than the slab and columned anodes; due to the three-phase interface, forest-like cathode's output power density is increased 47% and its limiting diffusion current is increased 161%, in comparison with the disc-shaped cathode. Therefore, we tested that the electrode shape can directly affect the performance of BMFC. Our results give a good instruction on the design of the battery looks.Second, we carried out the chemical modification of graphite anode to improve the performance of BMFC. A new modified reagent-Fenton reagent was added to the graphite anode. The hydroxyl and carbonyl groups were introduced on the modified anode surface; the contact angle was decreases from 82°to 48°, indicating a significant hydrophilic improvement. Tafel curve shows the exchange current density before and after modification were respectively 0.05 A/m2 and 0.17 A/m². It shows that the activity of the electrode kinetics was greatly increased. After modification, the maximum value of output power density of BMFC was increased 64%. The introduced hydroxyl and carbonyl groups act as electron transfer mediator, significantly enhance the activity of the electrode kinetics, increase the number of bacteria adsorbed on the anode surface and accelerate the anodic reaction, so as to improve the battery performance. Such an anode material has a potential application in developing BMFC.At last, we assembled the netlike electrodes into a BMFC device and used it to degrade benthonic sediment waste. During the operation of the BMFC, we periodically detected the content of Fe³⁺, Mn²⁺, S^2-, and organic carbon in the deposits. The results show that BMFC has almost no degradation effects on Fe³⁺, Mn²⁺; but to a certain extent, accelerates the degradation of S^2-s and organic carbons. If BMFC's output power were further increased, the degradation effect would be more apparent.