Self-stratified and self-powered micro-supercapacitor integrated into a microbial fuel cell operating in human urine

Abstract

A self-stratified microbial fuel cell fed with human urine with a total internal volume of 0.55 ml was investigated as an internal supercapacitor, for the first time. The internal self-stratification allowed the development of two zones within the cell volume. The oxidation reaction occurred on the bottom electrode (anode) and the reduction reaction on the top electrode (cathode). The electrodes were discharged galvanostatically at different currents and the two electrodes were able to recover their initial voltage value due to their red-ox reactions. Anode and cathode apparent capacitance was increased after introducing high surface area activated carbon embedded within the electrodes. Peak power produced was 1.20 ± 0.04 mW (2.19 ± 0.06 mW ml −1 ) for a pulse time of 0.01 s that decreased to 0.65 ± 0.02 mW (1.18 ± 0.04 mW ml −1 ) for longer pulse periods (5 s). Durability tests were conducted over 44 h with ≈2600 discharge/recharge cycles. In this relatively long-term test, the equivalent series resistance increased only by 10% and the apparent capacitance decreased by 18%.

Boosting Microbial Fuel Cell Performance by Combining with an External Supercapacitor: An Electrochemical Study

“…[60] Simple carbonaceous-based materials used in this work as electrodes for MFCs were shown previously to display supercapacitive features and enhance power output. [63][64][65][66] In this study, the peak in power curves showed during the polarization curve was 0.56 mW while the peak in power determined during galvanostatic discharge was 1.4 mW (at i pulse of 4 mA over 1 s) which was 2.5 times higher despite operated intermittently. The supercapacitive operation, therefore, present benefits compared to the continuous operation.…”

“…The MFCs operation mode in intermittent and supercapacitive mode introduced recently in 2016 explores the galvanostatic discharges of the MFC electrodes considered like an internal supercapacitor . Simple carbonaceous‐based materials used in this work as electrodes for MFCs were shown previously to display supercapacitive features and enhance power output . In this study, the peak in power curves showed during the polarization curve was 0.56 mW while the peak in power determined during galvanostatic discharge was 1.4 mW (at i pulse of 4 mA over 1 s) which was 2.5 times higher despite operated intermittently.…”

“…[45][46][47][48][49][50][51][52][53] The different possible combinations of MFC and power management systems are described in detail in a recent review. [54] Recently, also the capacitive features of MFCs anode [55][56][57][58] and cathode [59][60][61][62][63][64][65][66] electrodes have been explored considering the MFCs electrodes as the electrodes of an internal supercapacitor. Therefore, MFCs were discharged like a supercapacitor and the electrodes were self-recharged thanks to different anaerobic and aerobic environments occurring on the MFC anode and cathode.…”

Urine in Bioelectrochemical Systems: An Overall Review

“…A single cascade of 6 modules electrically connected in series produced a continuous electrical output of 2.5 V at 40 mA (100 mW), and was able to power 3 h of continuous phone communication every 6 h, with as little as 600 mL urine every 6 h. [70] Beside urine treatment and power generation, this type of design was also applied to the development of internal selfpowered supercapacitive MFCs fed with human urine. [73] Supercapacitor MFCs (empty volume 550 μL) were shown to produce a peak power of � 1.20 mW ( � 2.19 mW ml À 1 ) for a pulse time of 0.01 s that decreased to � 0.65 mW ( � 1.18 mW ml À 1 ) for longer pulse periods (5 s). Moreover, these microbial supercapacitors demonstrated relatively stable operation over 44 h with � 2600 recharge/discharge cycles.…”

“…Beside urine treatment and power generation, this type of design was also applied to the development of internal self‐powered supercapacitive MFCs fed with human urine . Supercapacitor MFCs (empty volume 550 μL) were shown to produce a peak power of ≈1.20 mW (≈2.19 mW ml −1 ) for a pulse time of 0.01 s that decreased to ≈0.65 mW (≈1.18 mW ml −1 ) for longer pulse periods (5 s).…”