Electron‐transfer coupling in microbial fuel cells. 2. performance of fuel cells containing selected microorganism—mediator—substrate combinations

Abstract

Various phenoxazine, phenothiazine, phenazine, indophenol and bipyridilium derivatives were tested for their effectiveness as redox mediators in microbial fuel cells containing Alcaligenes eutrophus, Bacillus subtilis, Escherichia coli, or Proteus vulgaris as the active biological agent, and glucose or succinate as the oxidisable substrate. A ferricyanide-Pt cathode was used. The open-circuit cell e.m.f.'s increased in the order of increasing negative formal redox potentials at pH 7(Ez) of the redox compounds. Several of the redox agents worked well as mediators, maintaining steady currents over several hours, and thionine was found to be particularly effective in maintaining relatively high cell voltages when current was drawn from the cell. A number of the compounds tested did not function well, either because they were incompletely or slowly reduced by the microorganisms or because of their instability. P. vulgaris, with thionine as mediator and glucose as substrate, showed the best performance in a fuel cell. This system was examined in some detail under various conditions of external load to establish the effects of organism concentration, mediator concentration, and substrate addition. Coulombic outputs from these cells were calculated by integration of the current-time plots. Coulombic yields of 30-60% were obtained, on the basis of (theoretical) complete oxidation of added substrate to C02 and water.

Modelling microbial fuel cells with suspended cells and added electron transfer mediator

“…This modelling study is based on the detailed experimental observations by Bennetto's group in the 1980s [5,21,24] and Kim's work in the late 1990s [11]. For convenience, their experimental setup is briefly described here.…”

“…Batch operation of the MFC is simulated (experiments by Kim et al [11], Thurston et al [24]. Alternatively, repeated substrate addition in a fed-batch mode is also considered (experiments by [5]. Soluble components diffuse between the bulk liquid and the electrode through a mass transfer boundary layer (MTBL) of thickness, L L , adjacent to the anode.…”

“…In this model we describe in detail only the dynamic behaviour of the anodic compartment, having in mind that a description of the cathodic chamber can follow the same approach. The model will be used to interpret experimental data obtained by Bennetto's group on MFCs with added soluble mediator (thionine) and suspended Proteus cells [5,21,24]. Such a model is also useful because it points to parameters that still need to be measured.…”

Investigation into effects of cathode aeration on output current characteristics in a tubular microbial fuel cell

“…Most MFCs are structurally similar to other fuel cells; they are electrochemically inactive and require mediators to facilitate the transfer of electrons (Delaney 1984). Utilization of microbes which are electrochemically active was a major step in the manufacture and advancement of microbial fuel cell reactors (Kim et al 1999a, b).…”

Redox-Polymers Enable Uninterrupted Day/Night Photo-Driven Electricity Generation in Biophotovoltaic Devices

“…[2][3][4] Previous research efforts have focused on maximising current output by utilising soluble electron mediators which allow for electron transfer from the enzymatic active sites within the cells to the electrodes. [5][6][7][8][9] Nevertheless, the use of soluble mediators requires continuous replenishment, which makes their use unsustainable, costly and in some cases even harmful to the environment. 7,10 Recent investigations in the field of bioelectronics have demonstrated that electron shuttling via immobilized redox mediators such as polymeric osmium complexes 11,12 and polymeric azines [13][14][15] (e.g.…”