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Summary: Microbial fuel cells (MFCs) are a promising technology that uses microorganisms to simultaneously generate bioelectricity while treating wastewater. To further improve the performance of the MFC, it is essential to understand and evaluate the electron transfer mechanism. However, redesigning the electron transfer mechanism of MFCs through an experimental approach is costly and time‐consuming. Hence, in this study, a numerical modeling approach is implemented through the Nernst‐Monod kinetic equation, which is validated by experimental results. A nanowire conductive transferring pathway is considered between the microorganisms and anode electrodes of a batch‐type MFC. Moreover, two types of bacteria are utilized such as the Shewanella oneidensis MR‐1 and Shewanella putrefacient with substrate concentrations of 0.5 M sodium lactate. The results have shown that the limiting current density of the MFC from the computational model is 1514 mA m−2. On the other hand, the current density from the experimental approach for Shewanella oneidensis MR‐1 is 497 mA m−2 while for Shewanella putrefacient is 140 mA m−2. The anode activation loss of 491 Ω is lower than the cathode activation loss of 643 Ω, which indicates the relative influence of the cathode activation loss on the bioelectricity generation of the MFC. In addition, the results revealed that the nanowire electron transfer mechanism in the anode biofilm was less affected by the concentration losses. This then indicates that the physical mechanism of the nanowire electron transfer can be effectively used to investigate the batch‐type MFCs. In turn, the results of this study will contribute to the development of an improved MFC. Highlights: Nanowire electron physical transfer was applied in batch‐type MFCs.G. sulfurreducens and S. oneidensis were made in MFCs.Power generation and biofilm thickness were observed in the MFCs.Bioelectricity transfer proved will be useful to the application of MFC. [ABSTRACT FROM AUTHOR]

Summary: Microbial fuel cells (MFCs) are considered as power generation devices for sustainable energy. However, the power generated is insignificant compared to other energy production devices. In this study, a mini autonomous biosensor (MAB) based on MFCs has been designed for detecting hazardous hexavalent chromium in wastewater. Hexavalent chromium has been classified as a human carcinogen causing serious birth defects due to its mutagenic and teratogenic properties. The power generated by the MAB has been investigated to study the feasibility of providing power to itself. In addition, electrochemical analyses of conductive silver paste and carbon cloth as the anode were conducted in the MAB for detecting hexavalent chromium in the anode chamber. Results show that a maximum voltage of 518.17 mV and a power density of 1.075 mW/cm2 could be achieved using carbon cloth with an external resistance of 1000 Ω, while a higher limiting current density of 0.015 mA/cm2 could be achieved with conductive silver glue as the anode electrode. Besides, the voltage output of the MAB decreased rapidly with the addition of hexavalent chromium into the wastewater. Also, the recovery time for the MAB was much shorter than found in previous studies. The MAB demonstrated potential for simultaneous production of electricity and detection of hexavalent chromium, which would open up avenues for autosensing applications in the environment as well as smart powering devices. Results indicate that the MAB with conductive silver glue as anode electrode is feasible for detecting hexavalent chromium in wastewater. [ABSTRACT FROM AUTHOR]