Research On The Influence Of Structure And Functional Groups Of Activated Carbon As Air-cathode On The Performance Of Microbial Fuel Cells

In recent years,the demand of people for energy increases with the the development of technology and enconomy.In order to solve the problem,the study of microbial fuel cell?MFC?emerges at the right moment.MFC is a renewable energy technology that simultaneously achieves energy recovery and wastewater treatment.However,the study of MFC is still at the initial stage in the world.The operating feasibility and cost are always the big problems to be urgently solved.So,it is difficult for scientists to improve the output of MFC.In view of the application problems of MFC,the performance and application of air cathodes that used activated carbon?AC?as catalyst layer was studied.To be our best knowledge,AC is an inexpensive and superior active catalyst with large surface area.Besides,AC is usually used as support to be doped with metal or metal oxide.So,in order to expand the application of AC,the pore structure,surface area,degree of graphitization and functional groups were researched in this work.Moreover,the acid treatment of AC and synthesis AC from chitosan were also explored in this study.In order to analysis the influence of pore structure on electrochemical performance of AC,carbon samples with different pore structures were prepared as air-cathode catalyst layer.The electrochemical measurements showed that the commercially-produced activated carbon?CAC,SAC-20?had the best electrochemical performance,and carbon samples with only micropore or mesoporous showed lower performance than CAC.CAC possessed highest surface area(1616 m² g^-1)and a certain amount of micropore and mesoporous.According to Tafel plot and rotating disk electrode?RDE?,CAC behaved the highest kinetic activity and electron transfer number,leading to the improvement of oxygen reduction reaction?ORR?.The air permeability test proved that mesoporous structure enhanced oxygen permeation.Samples were analyzed by In situ Fourier Transform Infrared Spectroscopy and H₂ temperature programmed reduction,which indicated that micropore provided active sites for catalysis.Thus,micropore and mesoporous together would improve the electrochemical performance of carbon materials.A commercial activated carbon?AC,YEC-8A?was subjected to various kinds of acid treatment,which was employed as air cathode for Microbial fuel cells?MFCs?.Obviously,both acid types and concentration of acidic solution would effect on catalytic activity of AC,and the electrochemical performance of AC was increased after acid treatment.Cathodes using 1 M H₃PO₄ treated AC?AC-H₃PO₄-1?showed the maximum power density(1546±43 mW m^-2),which was 115%higher than the pristine AC.The electrochemical studies showed that AC-H₃PO₄-1 exhibited the least resistance and highest kinetic activity.In addition,the acid treatment could increase the total surface area and pore volume,especially the exposure of mesopore to the reactants.The degree of graphitization,surface oxygenic functional groups and acid sites of AC were enhanced due to acid treatment,which facilitate the ORR of AC.However,too much strong acidic functional groups were detrimental to the ORR.In short,proper aicd treatment would increase the electrochemical performance of AC.Chitosan with rich of nitrogen was used as carbon precursor to synthesis activated carbon?CH?through directly heating method in this study,which was aim to explore the application of AC air cathodes in MFC.The obtained carbon was activated by different amount of KOH and different temperature,and then prepared as air cathodes for MFCs.CH treated with double amount of KOH at 850??CH-2-850?exhibited maximum power density(1435±46 mW m^-2),which ascribed to the highest surface area(2334 m² g^-1)and the doping of nitrogen.The electrochemical impedance spectroscopy?EIS?and powder resistivity stated CH-2-850 possessed low resistance.Tafel plots and EDE demonstrated that the best kinetic activity made CH-2-850 to show the best electrochemical performance for ORR.Besides,the degree of graphitization of CH increased with the activated temperature increasing.According to elemental analysis and X-ray photoelectron spectroscopy?XPS?,all CH were doped with nitrogen,and high content nitrogen?pyridinic-N?improved the ORR activity of CH-2-850.Thus,AC derived from chitosan would be an optimized catalyst for ORR in MFC.