Improvement of a Microbial Bio-Cathode through Electrode Material

Improvement of a Microbial Bio-Cathode through
Electrode Material Selection
Manuel Gacitua1, Federico Aulenta2, Bernardo González1, Mauro Majone3
1
Laboratorio de Bioingeniería, Facultad de Ingeniería y Cs. Universidad Adolfo Ibáñez
Av. Diagonal Las Torres 2700, Edificio C, Santiago. E-mail: [email protected]
2
Istituto di Ricerca sulle Acque - Consiglio Nazionale delle Ricerche (IRSA-CNR)
3
Dipartimento di Chimica, Università di Roma “La Sapienza”
Microbial electrochemical reactors design requires further fundamental research on
each of their parts. One way to improve the system could be to optimize cathode
functioning, by testing alternative materials. The strategy selected was to study
hydrogen evolution using stainless steel (SS) and SS modified with a polyaniline layer
(PANI) in an already proved Desulfovibrio Paquesii hydrogenogenic electrochemical
system that used bare graphite electrodes.
0.2
J / mA cm-2
0
−0.2
−0.4
Graphite
SS
PANI
−0.6
−0.8
−1.2
−1.0
−0.8
−0.6
−0.4
−0.2
(a)
0
(b)
0.2
E / V vs Ag|AgCl
Figure 1 Cyclic Voltammetry Profiles at 10 mV s-1 (a) and Potentiostatic Hydrogen Production at -1.10
V vs Ag|AgCl (b) of Different Systems in Mineral Medium Inoculated with Desulfovibrio Paquesii.
Hydrogen evolution takes place at ca. -0.80 V vs Ag|AgCl or more negative and
current density values (J) should be proportional to electro-activity (Fig. 1a). Both
electrodes, SS and PANI, surpass on current the activity of a bare graphite electrode of
same nominal surface area. Nevertheless, PANI is less active than SS, making the
modification uneffective. The same situation is observed when hydrogen production is
monitored in a potentiostatic experiment (Fig. 1b). Since the cathodes are poised at
highly reductive potentials, PANI films might suffer from passivation to some extent,
since it’s known that polyaniline layer are more conductive on its oxidized form.
However, when reviewing the Coulombic Efficiency (CE) values the situation is
different. CE represents the percent of electrons that were effectively transformed into
H2. For Graphite, SS and PANI electrodes values of CE were 4.2, 56.8 and 74.2 %
respectively. Then, it can be noticed that microbiologically guided hydrogen generation
is more efficient over PANI electrode, despite being less productive. Probably, the
polymer surface roughness is more appropriated for microorganism interaction. Further
attempts will be made using more suitable polymer for cathode design, e.g. Poly(3,4Ethylenedioxythiophene).
The authors thank financial support from FONDECyT Chile trough grant 3130332.
ise140084

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