Cathodes biocathodes

In addition to chemical cathodes, biocathodes have also been developed, and actually fit much better with the sustainable nature of BBSs than chemical cathodes. Therefore, there is increasing interest in the development of biologically driven cathode reactions, as has been demonstrated by the increasing number of biocathode studies in recent years, from two publications in 2004 to 41 in 2010 (Web of Knowledge, keyword biocathode ). 

A construction of a biofuel cell is schematically illustrated in Fig. 23. A carbon felt sheet was used for both anode El and cathode E2. An anion-exchange membrane 180 /am thick was used for a separator membrane S. The contact area of S with the electrolyte in each compartment was 12.5 cm. Each compartment had an electrolyte solution (adjusted to pH 7.0 with NaH2P04 and Na2HP04) of 5 mL. The cell was used as a prototype biofuel cell to evaluate the performance of the fuel cell composed of a biocathode (ABTS / ABTS -B0D-02/H20) and a bioanode (MV /MV -Z). vulgaris (H)-2H /H2). The biofuel cell was operated with O2 and H2 gas bubbling in the cathode and anode compart-... 

C.J.N. (2010) Cathode potential and mass transfer determine performance of oxygen reducing biocathodes in microbial fuel cells. Environ. Sci. Technol,... 

Boon, N., Fan, M.Z., Zhang, L, and Zhang, X.Y. (2009) A completely anoxic microbial fuel cell using a photo-biocathode for cathodic carbon dioxide reduction. Energy Environ. Sci.,... 

Cathodic biofilms are biofilms that accept electrons from an electrode, as opposed to anodic biofilms, such as the G. sulfurreducens biofilms discussed previously, which deliver electrons to an electrode [34]. Cathodic biofilms are less well understood than their anodic counterparts despite being well documented in biocathode studies. Often, a more operational definition is given to cathodic biofilms. For example, biofilms that... 

Microsensors and CV can be coupled to assess ORR in cathodic biofilms operating in aerobic environments and to investigate cathodic reaction mechanisms operating in biocathodes in SMFCs and other bioelectrochemical systems. 

The OCP of a BFC is determined when there is no current flowing across the device C/max = 0) and thus, no bioelectrocatalysis is taking place at either the bioanode or the biocathode. As previously discussed, the use of an electron mediator requires a potential difference between the electron mediator and the enzyme s cofactor. This therefore can result in lower OCPs of BFCs, since the potential at both the bioanode and the biocathode is determined by the onset potential of the anodic electron mediator (F J and cathodic electron mediator (F ) 7). In... 

Much as bacteria catalyze the anode reaction in an MFC, bacteria can also catalyze the terminal reduction reaction at the cathode (Rabaey et al., 2003). Biocathodes are both low-cost and sustainable making them an attractive research area. However, biocathodes have not made much of an impact in the MFC field yet as power densities to date have been quite low. These low power densities appear to be mainly a product of oxygen mass transfer limitations associated with diffusion through a biofilm (Clauwaert et al., 2007). Measured current densities for biocathodes were significantly lower than their Pt counterparts but may have other advantages such as being able to reduce several different oxidized contaminates, such as Cr(IV) and Cr(OH)3 (Clauwaert et al., 2007 Ter Heijne, 2010). 

Fig. 4.1 I-shaped microfluidic biofuel ceU with mixed reactant supply of an oxygen-saturated glucose solution. The highlighted reaction zone (a) is magnified to illustrate the electrode configuration (a ), with the biocathode located upstream from the bioanode, and the growth of the oxygen concentration boundary layer formed on the cathode (a")- Reproduced with permission from Togo et al. [24]. Copyright Elsevier (2008)...

Laccase has been commonly used in cathodes of en2yme-based biofuel cells. Only recently, it was discovered that bacteria can also catalyze the oxygen reduction reaction in MFCs. Biocathode here refers to bacteria-based cathode. 

You, S.-J., Ren, N.-Q., Zhao, Q.-L., Wang, J.-Y., and Yang, F.-L. (2009) Power generation and electrochemical analysis of biocathode microbial fuel cell using graphite fibre brush as cathode material. Euel Cells, 9 (5), 588-596. 

Fig. 11 (A) Schematic configuration of the EEC prototype working from glucose and O2 as fuel and oxidant, respectively. (B) Euel cell performances obtained with the biocathode and the bioanode in a phosphate-buffered solution (pH 7.4) containing 10 mM glucose at 37°C. A saturated O2 solution circulates in the interior of the inner cathode tube. (- -) initial performances (- -) after 3 operating hours (-A-) after 3 operating hours and 2 days of storage at 4°C. Adapted with permission from [98]. Copyright (2008) Elsevier...

Blue multicopper oxidases (BMCOs) such as laccase, ceruloplasmin, bilirubin oxidase (BOx), and ascorbate oxidase (AOx) have been extensively investigated as cathodic biocatalysts for DET-based biodevices [44]. BMCOs have a catalytic center consisting of four coppers a type 1 (Tl) Cu site, which accepts electrons from the substrate and from the electrode surface, and a type 2/type 3 (T2/T3) cluster, where O2 is reduced directly to water. High redox potential laccases and BOx, with redox potential up to 780 and 670 mV versus normal hydrogen electrode (NHE), respectively [44,45], can be used to create efficient biocathodes with current densities up to a few mA cm . In 2012, Shleev and coworkers used the DET ability of these enzymes to create several completely DET-based BFCs [42]. The enzymes have also been used in different MET-based approaches [46,47] specifically, Heller and coworkers... 

MFCs use similar configurations as MFCs, with necessary modification due to the requirement for gas collection. The anode is usually made of carbon material for electron transfer and attachment of exoelectrogens. For the cathode, initial studies use a platinum (Pt)-coated material (Liu et al., 2005). However, Pt is expensive and Pt electrodes are easily poisoned by carbon monoxide or sulfur, so researchers started to search for Pt-free electrodes. One study compared Pt and Pt- ree electrodes, and found that once the applied voltage exceeds 700 mV, Pt does not have any additional effects on hydrogen evolution. In recent years, biocathodes have emerged as a promising alternative to Pt cathodes (Rozendal et al., 2008 Jafary et al., 2015). 

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