Hydrogen production enhancement in a cylindrical single-chamber microbial electrolysis cell with a triple-layer coaxial electrode structure

초록

Microbial electrolysis cells (MECs) have garnered increasing interest for their dual role in wastewater treatment and resource recovery, particularly hydrogen (H-2) production, with significantly lower energy input than conventional water electrolysis. Among various configurations, the cylindrical single-chamber MEC featuring coaxial, twisted electrodes offers notable advantages in design compactness and operational simplicity. This study presents, for the first time, a direct comparison between two typical double-layer coaxial electrode configurations, including the external anode-internal cathode (AC-MEC) and the external cathode-internal anode (CA-MEC). Results indicated that AC-MEC outperformed CA-MEC by 15-60%, likely attributed to its larger anode surface area, which potentially promoted electroactive biofilm development and substrate oxidation. Building on these findings, a triple-layer coaxial electrode configuration (i.e., anode-cathode-anode, namely ACA-MEC) was proposed by inserting an internal anode into the AC-MEC. Under an external voltage of 0.8 V and using dark fermentation effluent derived from brown macroalgae Sargassum polycystum, the ACA-MEC demonstrated superior performance to the AC-MEC. Notably, the volumetric hydrogen production rate increased by similar to 40% (1.03 +/- 0.05 vs. 0.74 +/- 0.03 L-H-2/L-working-reactor/d), suggesting enhanced cathodic activity from dual-sided exposure. Furthermore, cumulative hydrogen yield, energy recovery, and COD removal were improved by 9-16%, reaching 835.2 +/- 32.6 mL-H-2/g-CODfed, 148.2 +/- 2.1%, and 74.2 +/- 2.3%, respectively. These findings highlight the effectiveness of the triple-layer coaxial electrode configuration in enhancing MEC performance and suggest its potential for efficient application in other bioelectrochemical systems.

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