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Inefficient extracellular electron transfer within bioanode leads to low current production by microbial fuel cell (MFC). In this study, magnetite was sprinkled in electroactive biofilm with the aid of magnet field. Magnetite located inside biofilm (interior-doped biofilm) facilitated the electron delivery of electroactive bacteria far away from electrode surface. Electron transfer efficiency was improved by 12% and 37% compared with that of biofilms with magnetite located at the interface of biofilm/electrode (surface-doped biofilm) and that without any magnetite (control biofilm) respectively. The output power density of MFC with interior-doped biofilm (764 ± 32 mW m −2 ) was greatly increased compared with that of MFCs with surface-doped biofilm (604 ± 22 mW m −2 ) and control biofilm (475 ± 12 mW m −2 ). SEM images showed that magnetite evenly distributed inside the interior-doped biofilm and penetrated the electroactive biofilm, which would facilitate extracellular electron transfer across electroactive biofilms and thus improving the bioelectricity production. [ABSTRACT FROM AUTHOR]

A binder-free, pseudocapacitive anode was fabricated by coating reduced graphene oxide (rGO) and manganese oxide (MnO 2 ) nanoparticles on stainless steel fibre felt (SS). Microbial fuel cell (MFC) equipped with this novel anode yielded a maximum power density of 1045 mW m −2 , 20 times higher than that of a similar MFC with a bare SS anode (46 mW m −2 ). Transient-state regulation (TSR) was implemented to further improve the MFC’s power generation. The optimal TSR duty cycle ranged from 67% to 95%, and the MFC’s power density increased with TSR frequency. A maximum power density output of 1238 mW m −2 was achieved at the TSR duty cycle of 75% and the frequency of 1 Hz, 18.4% greater than that obtained from the steady state operation. The TSR mode delivered better MFC performance especially when the external resistance was small. Long-term operation tests revealed that the current density and power density yielded in the TSR mode were on average 15.0% and 32.7% greater than those in the steady state mode, respectively. The TSR mode was believed to reduce the internal resistance of the MFC while enhance substrate mass transfer and electron transfer within the anode matrix, thereby improving the MFC performance. [ABSTRACT FROM AUTHOR]

A successful pH control is of critical importance for ensuring efficient H 2 production in two-chamber MECs. In this study, a novel two-chamber MEC is developed with biotic/abiotic hybrid electrodes, which are composed of carbon felt (CF) and stainless steel (SS) mesh. The CF is used for the electrogenic microorganisms attachment catalyzing the oxidation of organic matter (OM); the SS serves as the current collector and the H 2 evolution catalyst. The MEC is operated in the periodic polarity reversal (PPR) mode and two hybrid electrodes work alternately as an anode and a cathode. With the hybrid electrodes and the PPR mode, the pH fluctuation is limited within the range of 6.4–8.6, and the H 2 production is 5.3 times that of control without the PPR mode. The optimal reversal interval is 2 h for maximal H 2 production. The H 2 production increases with the amplitude of the applied voltage (0.7–1.0 V). The using of hybrid electrodes, combining with the PPR mode, provides a simple but efficient pH control strategy and better H 2 production performance in MECs. The findings of this study are expected to facilitate the design of pilot-scale MECs or similar bio-electrochemical reactors in future research. [ABSTRACT FROM AUTHOR]