Impregnated thermoset pre-pressurized carbon composite electrodes in microbial fuel cell: Compositional functionalities influence on ORR with reference to graphite

Abstract

Advancement in developing specific compositional functionalities of electrodes that are energy-recovery efficient, cost-effective, durable and catalytically active is particularly challenging for microbial fuel cell (MFC) operation due to its bio-compatibility requirement. Compositional characteristics of the electrodes influence the electron charge-discharge rates, oxidation-reduction reaction and biofilm formation. In this study, compact carbon-carbon composite electrode (C/C composite), fabricated by high pressure hot-pressing method followed by densified low-pressure impregnation thermosetting carbonization, was evaluated as both anode and cathode in dual-chambered MFC with varied combinations with graphite electrode. Fed-batch experiments were operated with four combinations of electrode using 3 g/l glucose in designed synthetic wastewater as anolyte and oxygenated water as catholyte. C/C composite as cathode and graphite as anode (MFC-GC) depicted comparatively higher power density (0.37 W/m2) and current (2 A/m2) than the other configurations. Improved oxidation–reduction rate (ORR) kinetics enabled higher bioelectrogenic activity in MFC-GC with respect to the elemental and surface functionalities of C/C composite electrode. Bioelectrochemical analysis showed increased charge-transfer capacitance and electron flux while lowering the system losses in MFC-GC. The capability of C/C composite electrodes as cathode due to presence of higher oxygen functionalities and surface properties increased the oxidation-reduction rate kinetics towards higher energy output during MFC operation.