4-CP Degradation And Electricity Generation Characteristics In An Intimately Coupled Photocatalytic And Microbial Fuel Cell

The Microbial fuel cell（MFC）is regarded as the promising technology to regenerate energy from wastewater.However,the various substrates that have been explored in MFC are commonly biodegradable organics.The Photo fuel cell（PFC）can convert various organics to useful energy,from pure compunds to complex organic matters.But the ability of power generation is lower than MFC.To overcome these shortings,we put forward an intimately coupled photocatalytic and microbial fuel cell（PMFC）,based on the intimate coupling of photocatalysis and biodegradation.First,we prepared the visible-light-responsive photocatalycast Ag-TiO₂,with efficient photo degradation ability on parachlorophenol（4-CP）.At the optimical preparation conditons,the hydrothermal temperature and hydrothermal time were 130℃ and 5 h,respectively,the achieved photocatalyst reached 90% removal rate of 4-CP at 5 h.The photocatalyst characterization results demonstrated that the Ag-TiO₂ were existed in anatase pattern and showed strong visible-light-responsive.Then the intimately coupled of photocatalyst-biodegradation anode was prepared.The carbon foam was coated nano Ag-TiO₂ photocatalysts by alcohol dispersion method,and the Scanning electron microscope（SEM）showed that the porous structure was maintained.By considering the photocatalysis efficiency in different kinds and concentrations of electrolytes,the 50 mmol/L Na2SO4 was choosed as the optimical electrolytes,with 57% removal rate at 5 h.The Ag-TiO₂ coated carbon foam was used as anode to start up fuel cells.After seven days cultivation of the anode-respiring bacteria（ARB）without illumation,the fuel cell could generate stable and repeatable peaks in voltage,which meant the PMFC has been started-up successfully.The removal efficiency of 4-CP and electricity generation were researched systematically,by comparision with PFC and MFC directly.The PMFC had the best performance on 4-CP degradation.PMFC reached 50% of 4-CP degradation efficiency at 8 h,was 10% and 40% greater than that of PFC and MFC,respectively.The maximum power density of PMFC（910 mW/m2）was 1.1 times than the sum of PFC and MFC.The electrochemical impedance spectroscopy（EIS）showed less impedance,which was led by the semiconductor coated and greate microbial activity.Cyclic voltammetry（CV）analysis showed the oxidation-reduction current peaks of PMFC was twice than MFC,the mid-poingt potential of this redox pairs was estimated to be-0.217 V vs.SHE,which in good accordance with that of c-type cytochromes.The results showed that the 15 mg/L 4-CP had an obvious adverse effect on the stability of microbes on anode.The ability of power generation of microbes on MFC anode decreased during experiments,however,microbes of PMFC anode kept stable peak voltage（0.57 V）in less inhibitive situation caused by the 4-CP degradation by Ag-TiO₂.Confocal Laser Scanning Microscopy（CLSM）、SEM and Transmission Electron Microscope analysis demonstrated the microbes of PMFC anode were able to maintain higher microbial activity than MFC anode.Morever,PMFC anode could keep favourable cell morphology,while MFC anode appeared cytoplasm dissolution.By the high-throught sequencing,we ananlysis the change of biological community structure,the Alpha diversity results showed that PMFC had higher diversity of microbial community than MFC anode.The intimately coupled of photocatalys-biodegradation fuel cell was constructed successfully.According to 4-CP degradation efficiency and capacity of power output,the PMFC was proved tobe able to enhance 4-CP removal rate and power generation.These results demonstrate that PMFC may be a novel and promising process for realization of efficient power generation from bio-inhibitory and refractory organics.