The Effect Of Carbon Nanotubes And Graphene Oxide On Catalytic Capability Of Electrochemically Active Biofilm

Anode is the place to attach electrochemical active biofilm(EAB)as well as redox reaction in microbial fuel cells(MFCs),thus highly conductive anode materials and efficient anode modification methods have decisive effects on the electricity generation ability of MFCs.In this study,the simple,green and environmental friendly modification methods were used to improve electricity production ability of EAB on electrode surface including adopting carbon nanotubes(CNTs)and graphene oxide(GO).Meanwhile,the morphological characteristics of the biofilm growth on the electrode modified with CNTs and GO was also observed and analysed by scanning electron microscope and laser scanning confocal microscope.By using our methods,the electricity generation capability of EAB was significantly improved and novel structure of EAB was also obtained:(1)Various concentrations from 0 to 1000 mg/L of pristine CNTs,CNTs-OH or CNTs-COOH dispersed with growth medium were studied to evaluate the effects of CNTs on viability of Geobacter sulfurreducens,which provided a theoretical basis for the study of electricity generation of biofilm by using CNTs.(2)The electricity generation capability of EAB was significantly improved by two methods including modifying the electrode surface with each type of CNTs and doping CNTs suspension into EAB.The maximum current densities of EAB on the pristine CNTs,CNTs-COOH or CNTs-OH coated electrode increased by 112~125%,86~103% and 81~93% compared with that of the unmodified electrode,respectively.Meanwhile,the electricity generation capability of EAB in presence of CNTs-OH suspension in growth medium also showed the similar improvement.(3)CNTs were solubilized in the growth medium,using sodium dodecylbenzene sulfonate or chitosan as dispersant,respectively.The effects of using different CNTs solution to modify electrode surface on the electricity generation capability of EAB were studied.The electricity generation capability of EAB growth on CNTs-SDBS and CNTs-Chitosan coated electrode had no obvious increase.By comparison,the electricity generation capability of EAB growth on CNTs-growth medium coated electrode was significantly improved.(4)The architecture characteristics of the EAB on CNTs coated electrode and CNTs hybrid EAB with CNTs-OH suspension in growth medium were observed,respectively.A novel "sandwich" architecture of EAB consisting of two layers of biofilm and one layer of CNTs was obtained during EAB growth in presence of CNTs suspension for the first time.(5)The interaction between G.sulfurreducens and GO was investigated and the results indicated that GO can be reduced to MRGO efficiently by G.sulfurreducens as electron acceptor.Meantime,it also showed that GO and exoelectrogenic bacteria can form biofilm-MRGO nano-hybrid composite.The architecture characteristic of the MRGO hybrid biofilm was also observed,and the thickness of EAB increased obviously than that without GO.Especially,a novel porous biofilm by adding GO dispersion was found for the first time.(6)The effects on electricity generation capability of EAB by various methods of adding GO dispersion were studied.The results indicated that the electricity generation of EAB was improved and the maximum current densitiy increased by 89% through refreshing medium and adding GO dispersion after the mature biofilm formed on the electrode compared with that of the control group.