Electrochemical performance of microbial electrolysis cells based on an anode encapsulated in a cellulose acetate capsule

Anode encapsulation in microbial electrolysis cells (MECs) offers a promising strategy to modulate microbial community structure and enhance electron transfer. We evaluated encapsulated (Capsule-MEC) and non-encapsulated (Control-MEC) systems over 117 days across four phases: inoculation with Geobacter sulfurreducens, inoculation with Geobacter metallireducens, supplementation with carbon black nanoparticles, and supplied artificial wastewater. The Capsule-MEC exhibited enhanced interfacial electron-transfer kinetics, with lower charge-transfer resistance (153.20 vs. 459.10 Ω cm²) and lower biofilm resistance (39.08 vs. 57.39 Ω cm²) than the Control-MEC during the wastewater phase, alongside roughly 3-fold higher anodic charge density. Current density increased 3.6-fold under artificial wastewater conditions, reaching 3.09 A m⁻². Despite lower chemical oxygen demand removal under complex substrate operation (27.7% vs. 53.5%), the Capsule-MEC achieved substantially higher Coulombic efficiency (11.46% vs. 2.18%), suggesting more efficient electron recovery via suppression of non-electrogenic pathways. Hydrogen production followed a similar trend, reaching 0.065 m³ m⁻³ d⁻¹ during the wastewater phase. Microbial community analysis revealed strong selective pressure within the encapsulated environment, enriching electroactive Proteobacteria and increasing exoelectrogenic genera abundance from 54.89% to 78.07%, while suppressing fermentative populations. These findings indicate that anode encapsulation restructures the microbial consortium toward a specialized electroactive community and enhances MEC performance under complex substrate conditions.