The Foundational Investigation Of The Marine Electro-active Biofilms And The Application In The Microorganism Fuel Cells

Marine electro-active biofilms (electrochemical active biofilms, EABs) are kinds of functional biofilms in nature that can transfer the electrons produced by metabolizing organism to electrodes. The application of the EABs in inhibition corrosion, biosources and bioremediation has been studied extensively.In this paper, the influence of the marine natural biofilms on the corrosion of 316L SS was studied firstly. And the results showed that the marine biofilms can inhibit the corrosion of 316L SS. And then we systemically studied the electrons transfer process between EABs and electrodes and proposed the mechanism of electrons transfer between EABs and electrodes. And the application of EABs in MFCs was studied.The OCP (open circuit potential) of 316L SS ennobled 500mV vs. Ag/AgCl. The marine biofilms increased the pitting potential of 316L SS from 0.05V to 0.54V and increased the impedance. And the Electron microscopy (EMS) and Energy-Dispersive Spectroscopy (EDS) found there was no corrosion production on the 316L SS surface. So we made the decision that the marine biofilm can inhibit corrosion of the 316L SS. The cyclic voltammograms (CV) showed that the marine biofilms accelerated the electron transfer, catalyzed the cathode reaction. So we presented the inhibition mechanism of marine biofilms on 316L SS. The marine biofilms have electrochemical active to transfer electron between the biofilms and 316L SS. And the 316L SS can accept electron transferred by marine biofilms to avoid the corrosion.And then we used the graphite, glasscarbon and carbon paper electrodes to validate the EABs.The ennoblement of glasscarbon and graphite OCP in seawater were firstly studied. The glasscarbon ennobled positively 300mV vs. Ag/AgCl, and the graphite ennobled positively 50mV vs. Ag/AgCl. And the ennoblement trends of the two electrodes were in common with 316L SS and were agreed with the trends of the biofilm's growth: the first ennoblement slowly, exponent period, and then the platform period.The CV and EIS showed that the marine biofilms attached on graphite, glasscarbon and carbon paper electrodes catalyzed the cathodic reduction effectively and decreased the impedance that showed that the marine biofilms were EABs and can transfer electrons. The ability of the catalysis descended according to the sequence graphite, 316L SS, carbon paper and glasscarbon.We farther studied the marine deposition-seawater Microorganism fuel cells (MFCs). The MFCs were set up with graphite as anode and graphite or 316L SS as cathode. The stainless steel electrodes gave current densities 2 times higher than graphite. And the trends of the power and current increasing were agreed with the trend of the biofilm's growth. So it is important significance to enhance the 316L SS surface quality and screen electroactive biofilms to be used in MFC.