Quantifying Synergistic Energy Losses Induced by Internal Resistance in Microbial Fuel Cell Bioanodes: The Role of Physical Connectivity and Ionic Strength

by Nor Syazwanie Mohd Saidi, Muhammad Farhan Hil Me, Yashawini Phriya Rauichandran, Ryan Yow Zhong Yeo, Mohammad Sherjeel Javed Khan, and Swee Su Lim

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https://doi.org/10.17576/myjea.2026.01.1

Abstract

Internal resistance Rint is a critical bottleneck that dictates the power output and efficiency of microbial fuel cells (MFCs). This study investigates the synergistic impact of gradated internal resistance on bioanode performance by systematically manipulating electrode contact integrity to establish three distinct Rint levels: 20 Ω (Group 1), 60 Ω (Group 2), and 182 Ω (Group 3). Results indicate that elevated Rint triggers a cascade of potential energy losses; Group 3 exhibited a 22% reduction in peak power density (0.07 W/m2) compared to the optimized Group 1 (0.09 W/m2). Electrochemical Impedance Spectroscopy (EIS) identified the anodic interface as the primary site of degradation, with interfacial resistance (R2) surging from 3 Ω in Group 1 to 140.19 Ω in Group 3. Cyclic Voltammetry (CV) revealed that high Rint might have altered the redox behavior in the electrogenic biofilm, evidenced by a +0.36 V positive transition in midpoint potential (Emid), suggesting increased electrochemical energy demand and altered apparent redox behavior. Furthermore, sensitivity analysis via One-Factor-at-a-Time (OFAT) optimization identified a 10:5:50 mM (NaAc:NH4Cl:PBS) electrolyte ratio as optimal, driving current density to a peak of ≈ 2.1 A/m2 by mitigating secondary chemical bottlenecks. These findings suggest that poor connection is not merely a hardware failure but an electrochemical stress factor that affects the catalytic response of the bioelectrochemical interface.

Keywords: Bioanode kinetics, internal resistance gradation, electrochemical impedance spectroscopy (EIS), charge transfer resistance, microbial electron transfer pathways.

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