Scaling up self-stratifying supercapacitive microbial fuel cell

Abstract

Self-stratifying microbial fuel cells with three different electrodes sizes and volumes were operated in supercapacitive mode. As the electrodes size increased, the equivalent series resistance decreased, and the overall power was enhanced (small: ESR = 7.2 Ω and P max = 13 mW; large: ESR = 4.2 Ω and P max = 22 mW). Power density referred to cathode geometric surface area and displacement volume of the electrolyte in the reactors. With regards to the electrode wet surface area, the large size electrodes (L-MFC) displayed the lowest power density (460 μW cm −2 ) whilst the small and medium size electrodes (S-MFC, M-MFC) showed higher densities (668 μW cm −2 and 633 μW cm −2 , respectively). With regard to the volumetric power densities the S-MFC, the M-MFC and the L-MFC had similar values (264 μW mL −1 , 265 μW mL −1 and 249 μW cm −1 , respectively). Power density normalised in terms of carbon weight utilised for fabricating MFC cathodes-electrodes showed high output for smaller electrode size MFC (5811 μW g −1 -C- and 3270 μW g −1 -C- for the S-MFC and L-MFC, respectively) due to the fact that electrodes were optimised for MFC operations and not supercapacitive discharges. Apparent capacitance was high at lower current pulses suggesting high faradaic contribution. The electrostatic contribution detected at high current pulses was quite low. The results obtained give rise to important possibilities of performance improvements by optimising the device design and the electrode fabrication.

Investigating Air-Cathode Microbial Fuel Cells Performance under Different Serially and Parallelly Connected Configurations

“…Walter et al [5] studied the potential of scaling up a self-stratifying MFC operating in supercapacitive mode. They tested cells with different electrodes area (from 6 cm 2 to 12 cm 2 and 18 cm 2 ) and reactor volumes of 49 mL, 68 mL, and 88 mL.…”

Electrosynthesis, modulation, and self-driven electroseparation in microbial fuel cells

“…In the above demonstration, the driver cells were used explicitly for the function of periodically driving the working cells. The advantage of this configuration is the utilization of cell recovery (after being polarized) and of the capacitive properties of MFCs ( Ieropoulos et al., 2005 ; Walter et al., 2020 ), which allows a repeated instantaneous delivery of proportionately high-energy bursts. This is visible in Figure 3 A, in which the driver waveform resembles a discharging capacitor.…”

Moving bed capacitive bioanodes

“…The main difference between the two is that the bioanode with a capacitor is used with intermittent control, which requires a period without producing an electrical current in the circuit [85], whereas the fluidized granules are in intermittent contact, where the capacitive granules only discharge when they are in contact with the current collector [96]. Fixed capacitive bioanodes allow improved stability for scale up using stacked MFCs [192,198,199] and use of temporary operation for applications like robots and remote sensors [149]. The main advantage of the fluidized bed capacitive bioanodes compared to fixed capacitive bioanodes, is the ability to continuously produce a current [96,107].…”