Surface Modification And Corrosion Resistance Performance Of Stainless Steel Microbial Anode

Microbial fuel cell?MFC?is a bioelectrochemical energy technology that converts chemical energy into electrical energy by using electroactive microorganisms?EAMs?to decompose organic matter.In recent years,with the unremitting efforts of researchers,the theoretical basis research of MFC has gradually matured.At present,more attention is paid to the combination of MFC with practical application,especially in the field of sewage treatment,which has attracted extensive attention from researchers.The anode is a place for the growth of electrogenic microorganisms,and the electrochemical performance of MFC is affected by the growth number and electron transfer efficiency of microorganisms on the anode.Therefore,the improvement of MFC anode performance has great significance.At present,carbon materials are mostly used for anodes.Due to its good stability and biocompatibility,however,its poor mechanical properties and difficult to process,which is limited to some extent in practical applications.Stainless steel is widely used as a current collector for MFC in many studies due to its excellent mechanical properties,good electrical conductivity,and the advantages of easy processing.However,its biocompatibility is poor,get the production of current density is very low(only about0.02 A·m^-2),cause the stainless steel material is difficult to directly as the MFC anode used in practical application.In view of the above problems,the surface modification of stainless steel to improve the electrical properties of MFC anode and explore the corrosion resistance of stainless steel composites.The main research content includes the following two parts:?1?In order to improve the biocompatibility of stainless steel anodes and increase their bioelectrocatalytic properties,in this part,304 stainless steel?SS?was modified by low-temperature oxidation.The microbial electrocatalytic properties and corrosion resistance performance of the heat-treated stainless steel electrodes?SS-heat?were studied.Microbial electrochemical tests show that the bioelectrocatalytic performance of the SS-heat increased gradually with the increase of temperature;The SS treated at 400 ^oC?SS-400?genered the highest current of 0.91 mA·cm^-2,which was mcuh higher than the pristine SS.With temperature higher than 400^oC,the current density drop instead.Morphological characterization showed that the amount of microbial attached on the SS-400 electrode was more than that on the pristine SS electrode under the same condition,which was consistent with the results of microbial electrochemical test.Tafel tests showed that lower than 300 ^oC,with the increase of preparation temperature,SS-heat from the corrosion potential of electrode is moving;Heat treatment temperature of 300 ^oC when the preparation of the electrode from the corrosion potential of the biggest and best corrosion resistance;Higher than300 ^oC,with the increase of temperature,the corrosion potential of electrode negative shift,corrosion resistant performance degradation,and the temperature over 400^oC,the electrode in the process of testing corrosion will happen automatically.?2?In order to further improve the electrocatalytic performance of stainless steel,this part modified the surface of stainless steel electrode by vapor deposition,and studied its electrocatalytic performance and corrosion resistance.NFO-SS and CNM-SS were prepared as electrodes of MFC by chemical vapor deposition on stainless steel surface with a layer of nano-iron oxide?NFO?and carbon nanomaterial?CNM?.SEM morphological characterization showed that NFO grew vertically on the electrode surface in flake form,and CNM grew in fiber shape.The elements composition of the modified layer was confirmed by X-ray photoelectron spectroscopy?XPS?.Microbial electrochemical tests showed that the maximum current density generated by NFO-SS electrode was 1.06 mA·cm^-2,and the maximum current density generated by CNM-SS electrode was 1.28 mA·cm^-2,which were much higher than untreated stainless steel sheet.The possible reason is that NFO-SS and CNM-SS electrodes increased the biocompatibility of stainless steel.The increasing of the amount of electroactive microorganisms attached to the surface of electrode materials,which improved the bioelectrocatalytic performance.The Tafel test of NFO-SS electrode showed that the electric and self-corrosion potential of NFO-SS was negatively shifted by 50mV,and the self-corrosion current density increased by an order of magnitude,compared with the pure stainless steel sheet.Those evidences indicated the NFO-SS electrode was more easily corroded than the pure stainless steel.?3?A modified stainless steel electrode with high microbial electrocatalytic and corrosion resistance was prepared.In this part,carbon black modified the stainless steel composite electrode?SS/CB?was perpared with the processing of low temperature heat treatment.Microbial electrochemical tests showed that the bioelectric catalytic properties of SS/CB electrode higher than pure stainless steel electrode.With heat treatment temperature of 400 ^oC,its maximum current density reached 1.91 mA·cm^-2.The morphology of microorganism film observed by SEM,showed that the amount of microorganism attached on SS/CB electrode was much higher than that on SS electrode.Tafel test showed that the trend in corrosion resistance of SS/CB electrode in accordance with the SS electrode.The results showed that the self-corrosion potential of the modified electrode is the largest and the corrosion resistance is the best when the heat treatment temperature was 300^oC.While the heat treatment temperature higher than 400 ^oC,self-corrosion will occur during the testing of modified electrode.