Performance of Reduced Titanium Oxide and Boron Doped Diamond as anodes in hyperthermophilic bioelectrochemical systems

Laura Malavola,Pierangela Cristiani,Nunzia Esercizio,Silvia Franz,Giuliana D’Ippolito,Massimiliano Bestetti,V Cigolotti

doi:10.1051/e3sconf/202233408009

Abstract

This work investigates Reduced Titanium Oxide (RTO) in comparison with Carbon Cloth (CC) and commercial Boron Doped Diamond (BDD) as anodes in hyperthermophilic bioelectrochemical systems operating at 80°C by Thermotoga neapolitana. Two samples of RTO were synthesized by plasma electrolytic oxidation (PEO) of titanium plates and subsequent electrochemical reduction. Electrochemical performance of CC, BDD, and RTO are tested by performing cyclic voltammetry in the anodic region (0-1V, 50 mV/s), in abiotic and biotic conditions. The surface of colonized materials is observed by SEM microscopy. Results show that bacteria fast settle on all tested material, significantly affecting their electrochemical conductivity. The integration of voltammetric cycles reveals that biofilm generates capacitive effects on the anodic surfaces, particularly evident in RTO, less in CC and absent in BDD. Charge densities provided by capacitive response of RTO and CC are of the order of 5.58 and 0.77 mC/cm2, respectively.

Highlights

Thermotoga neapolitana are hyperthermophilic anaerobic bacteria, which produce hydrogen and lactate by metabolizing glucose
The presence of hyperthermophilic T. neapolitana is detected by means of Scanning Electron Microscopy (SEM) on all anodic materials, meaning that in principle all of them are feasible for the application in bioelectrochemical systems, and bacteria are attracted by their positive polarization
Comparisons have been made between Reduced titanium oxides (RTO), Boron Doped Diamond (BDD) and carbon cloth (CC) using the ATCC 1977 medium as electrolyte

Summary

Introduction

Thermotoga neapolitana are hyperthermophilic anaerobic bacteria, which produce hydrogen and lactate by metabolizing glucose In principle, they can be exploited to catalyze the hydrogen evolution reaction in a microbial electrolytic cell, improving the overall yield of the system, as recently demonstrated [1]. Carbon cloth is extensively used as electrode material for bioelectrochemical systems, since it provides very high surface area and porosity, as well as good conductivity, mechanical strength and flexibility. The objective of this work is to investigate the change of the electrochemical properties of different types of anodes, and in particular Reduced titanium oxides (RTO), colonized by Thermotoga Neapolitana. BDD is an inert anode, that is it does not participate in the reaction It is a p-doped diamond that exhibits chemical inertness, corrosion resistance, extremely high hardness, thermal conductivity and good charge carrier mobility.

Objectives

Methods

Results

Discussion

Conclusion