Addition of reduced graphene oxide to an activated-carbon cathode increases electrical power generation of a microbial fuel cell by enhancing cathodic performance

Abstract

Activated carbon (AC) is an inexpensive catalyst for oxygen reduction in an air cathode of microbial fuel cells (MFCs). In the AC-based cathode, carbon black (CB) is used as a conductive supporting material. In this study, it was hypothesized cathodic performance would increase if reduced graphene oxide (rGO) replaces CB in an optimum ratio. rGO replaced CB in the four different weight ratios of rGO toCB: 0:30 (rGO0); 5:25 (rGO5); 15:15 (rGO15); 30:0 (rGO30). Maximum power density was the best in rGO15 (2642 mW/m2) followed by rGO5 (2142 mW/m2). In the optimum external resistance operation, rGO5 and rGO15 showed similar power (∼1060 mW/m2), higher than the others. Linear sweep voltammetry, cyclic voltammetry, and impedance spectroscopy also showed that the optimal rGO additions improved cathodic performance and reduced cathodic internal resistance. Due to the flatter and wider shape of rGO and 5 times higher electrical conductivity than CB, the rGO addition improved the cathodic performance, but the complete replacement of CB with rGO decreased the cathodic performance due to the increased thickness and the morphological crack. The optimum rGO addition is a simple and effective method for improving cathodic performance.