| Microbial fuel cell(MFC)is the bioelectrochemical system that utilizes electroactive microorganism to convert chemical energy in the organic pollutants into electricity.For single chamber MFC,the activated carbon cathode has caused extensive attention due to the lower price and easier scalability.However,the still lower catalytic activity and stability are the main drawbacks.In this study,the mechanism and effect of pore structure and biofilm attachment on catalyst layer on cathode activity were studied,the cathode materials with higher catalytic performance and efficient anti-biofouling properties were synthesized by surface optimation,and the long-term performance of cathode was also tested.Pore structure of catalyst layer was changed by mixing NH4HCO3 pore former with activated carbon powder.With the weight ratio of carbon powder to pore former of 5:1,the porosity and specific pore area were increased by 37.8% and 3.3 times,respectively.Additionally,the porosity of micropores(< 0.8 ?m)increased by 28.4 times in comparison with the control cathode(without pore former).This not only increased oxygen transfer coefficient but also extended the three-phase interfaces,consequently,the maximum power density enhanced by 32.9%.The pore former decorated activated carbon cathode showed more stable catalytic activity compared to Pt/C cathode,revealing by the fact that the maximum power density of MFCs with carbon cathodes decreased by only 12.7% compared to 35.1% for the Pt/C cathode after four months due to the increased cathodic diffusion resistance.Biofilm not only covered the surface of cathode buy also clogged partial pores inside the catalyst layer after running for six months,as a result,the three-phase interfaces and oxygen permeability of cathode declined which impaired the catalytic activity of cathode.After removing surface biofilm and further removing biofilm inside the catalyst layer,oxygen coefficient increased gradually,and exchange current density enhanced by 8.6% and 34.5%,and charge transfer resistance decreased by 23.1% and 44.0%,respectively,and the maximum power density of MFC was gradually recovered.Further study demonstrated the current output declined and the overpotential enhanced after biofilm grew on cathode without carbon catalyst,indicating the bare acceleration of biofilm to oxygen reduction.The cathode materials with higher activity and anti-biofouling performance were fabricated by in-situ synthesis of silver nanoparticles on carbon powders and enhancement hydrophilicity of catalyst layer by LA132 binder.By loading silver nanoparticles,the maximum power density of MFC increased by 14.6%.After running for 150 days,the protein content in the biofilm was just 38.3% of that on activated carbon cathode.Thinner biofilm accelerated oxygen transfort and relieved OH-transfer resistance to the bulk solution,which resulted in less polarization loss.Enhanced hydrophilicity of catalyst layer by addition of LA132 binder into PTFE binder promoted wettability of three-phase interfaces,which further accelerated the protons transport to the reaction sites.When the LA132 content in the mixed binder was 67%,the maximum power density increased by 13.9%.In addition to the higher hydrophilicity,the addition of LA132 also introduced abundant negative charges,which greatly alleviated the microorganism adsorption and biofilm growth.Therefore,the protein content in the biofilm was just 52.5% of that on PTFE cathode after running for 150 days.The electricity generation from municipal wastewater in single chamber MFC with optimized cathode was tested.Compared to the PTFE based cathode(323±44 mV,411±5 mW/m2),the mixed-binder cathode achieved higher voltage of 398±15 mV and maximum power density of 453.9±24.2 mW/m2.The COD and TN removal of effluent were 90.2±3.6% and 80.3±8.3%,respectively.By lowering external resistance value,MFC generated higher current density while accelerating the COD and TN removal rate. |
PDF Full Text Request