Graphene Oxide Aerogel Modified Three-dimensional Anode Materials For Application In Microbial Fuel Cells

Microbial fuel cell（MFC）is a new technology extracting electrical energy from wastewater,which might offer a lot of possibilities for “zero-energy consumption” in wastewater treatment.However,the low power output of MFC is a roadblock which limits its practical application.Anode as the core part of MFC affects the power output and practical application by the extracelluar electron transport rate and its stability in long-term operation.Here,we aim to construct three dimensional（3D）graphene oxide aerogel（GOA）-modified 3D anode materials,in an effort to achieve high surface area,conductivity,biocompatibility and stability,all of which are highly desirable for application in MFCs.These 3D-3D structured materials are synthesized via the easy and facile freeze-drying method.Firstly,we investigate the effects of GOA concentration and type of 3D substrate on the power output of MFCs.The results showed that the MFC performance increased with the increase in concentration of GOA,with the maximum power density of 1204.5 mW/m2 obtained from the GOA-modified graphite fiber brush（GFB）anode with a GOA loading of 5 mg/mL.In addition,in comparison to stainless steel brush（SSB）and Ni-foam,the GFB substrate exhibits larger surface area,higher biocompatibility and more corrosion resistant,and is thus the most appropriate material to host GOA deposition.The maximum power density of GOA-GFB-MFC after 2 month-operation is 1.5 and 6 times higher than that associated with the GOA-SSB-MFC and GOA-Ni-foam-MFC,respectively.It is revealed that GOA can be in-situ reduced by Shewanella oneidensis MR-1 so that the anode conductivity increased after inoculation in MFCs.The design of 3D anode conducive to microbial colonization has gained considerable attention,since it can facilitate extracellular electron transfer（EET）and enhance power performance of MFCs;however,relatively little is known about its long-term durability,a crucial issue with respect to practical application.Then,we focus on evaluating the performance of GOA-GFB-MFC during 18-month operation.The long-term operation yields a continuous enhancement of power generation,with 53.8±6.0 W m^-3（normalized to anode chamber）achieved after 18 months,which suggested that the 3D-3D GOA-GFB is a high-performance MFC anode that can sustains the long-term enhancement.Lastly,our effort is made to recover energy from a real wastewater（i.e.,rice noodle wastewater）using MFCs with the GOA-GFB anode.The performance of MFCs in terms of normal energy recovery（NER）is compared between the intermittent and steady-state operation mode.The effects of charging and discharging time on NER and COD removal are evaluated.The results show that the MFC operated with 0.5 h charging time and 0.5 h discharging time achieves 1.25 kW h/kg COD energy,larger than 0.42 kW h/kg COD obtained from the steady-state mode,but COD removal（2.5%）is lower than the value（8.9%）obtained from the steady-state mode.