Biohybrid Cathode in Single Chamber Microbial Fuel Cell

Giulia Massaglia,Isabella Fiorello,Marzia Quaglio,Valentina Margaria,Adriano Sacco,Candido Pirri

doi:10.3390/nano9010036

Abstract

The aim of this work is to investigate the properties of biofilms, spontaneously grown on cathode electrodes of single-chamber microbial fuel cells, when used as catalysts for oxygen reduction reaction (ORR). To this purpose, a comparison between two sets of different carbon-based cathode electrodes is carried out. The first one (Pt-based biocathode) is based on the proliferation of the biofilm onto a Pt/C layer, leading thus to the creation of a biohybrid catalyst. The second set of electrodes (Pt-free biocathode) is based on a bare carbon-based material, on which biofilm grows and acts as the sole catalyst for ORR. Linear sweep voltammetry (LSV) characterization confirmed better performance when the biofilm is formed on both Pt-based and Pt-free cathodes, with respect to that obtained by biofilm-free cathodes. To analyze the properties of spontaneously grown cathodic biofilms on carbon-based electrodes, electrochemical impedance spectroscopy is employed. This study demonstrates that the highest power production is reached when aerobic biofilm acts as a catalyst for ORR in synergy with Pt in the biohybrid cathode.

Highlights

Microbial fuel cells (MFCs) are classified as bio-electrochemical devices, comprised of two different compartments: anode and cathode [1,2,3,4,5]
At the starting point of experiments, fresh anodes were used for all single chamber microbial fuel cells (SCMFC) and two different cathode electrodes were employed: i) a Pt-free, carbon-based cathode electrode on which an aerobic biofilm grows during this phase of the experiment, leading to the formation of a biocatalyst; ii) a Pt-based cathode that is formed by a Pt catalyst layer deposited on a carbon-based electrode combined with the biofilm that spontaneously proliferates on it
During the phase of experimentation, evaluatemade the key previously described, at the beginning of first experiments, fresh anodes andtocathodes of role played by biofilms grown on both electrodes, the overall performance of SCMFCs was assessed

Summary

Introduction

Microbial fuel cells (MFCs) are classified as bio-electrochemical devices, comprised of two different compartments: anode and cathode [1,2,3,4,5]. The main advantage of this kind of device is the capability of producing electrical energy, starting from chemical energy, contained in organic matter of different substrates, known as fuel. A specified class of microorganisms called exoelectrogenic bacteria, are able to directly convert chemical energy into electrical energy through the oxidation of organic matter, while in the cathode compartment, oxygen reduction reaction (ORR). As deeply investigated in the literature [6,7,8,9,10,11], one of the main limits of this configuration is the sluggish kinetics of ORR, which requires four electrons to directly reduce oxygen to water, leading to minimized hydrogen peroxide, an intermediate product that is harmful to microorganisms [10]. Many works focused their attention on the development of new catalyst layers, based on non-precious

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