Anode modifications

Improving the kinetic activity associated with the transfer of electrons to the anode could potentially improve MFC performance. To these ends, several different composites have been constructed and thoroughly tested. One study reported increased performance of graphite -Fe +, -Mn + and -neutral red composites (Park and Zeikus, 2003). A subsequent study observed an increase in kinetic activity of composites 1.5 to 2.2 times that of those associated with graphite controls. The composites tested combined graphite with one or two of a selection of minerals (Mn +, Ni +, Fe304) and mediators (anthraquinone-l,6-disulfonic acid (AQDS), 1,4-napthoquinone (NQ)) (Lowy et al., 2006). Additional research on various other anode metal modifications has shown limited success (Logan, 2008). 

Conductivity of the anode is important to MF C performance. One method that has been suecess-fully used to increase conductivity and current densities of MFC is the application of the eonductive polymer polyaniline (Schroder etal., 2003). However, performance was only improved temporarily as polyaniline was shown to be unstable and susceptible to microbial degradation (Niessen et al., 2004). While these findings would seemingly limit polyaniline s potential contribution to future MFC designs research has suggested that it may be possible to improve both the stability and performance of polyaniline by making composites combined with fluorine, carbon nanotubes (Qiao et al., 2007) and titanium dioxide (Qiao et al., 2008). 

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Closely related to the anode modifications described above, the use of a HIL material to improve charge injection into the OLED device has spawned a number of materials, which have been shown to provide benefits, particularly in terms of lower operating voltages and extended lifetimes of devices. 

L.S. Hung, L.R. Zheng, and M.G. Mason, Anode modification in organic light-emitting diodes by low-frequency plasma polymerization of CHF3, Appl. Phys. Lett., 78 673-675 (2001). 

ANODE MODIFICATION FOR ENHANCING OLED PERFORMANCE 6.2.1 Indium Tin Oxide Surface Treatment and Modification... 

The primary effect of the anode modification on the enhancement in luminous efficiency and the increased stability of OLEDs can be attributed to an improved hole-electron current balance. By choosing an interlayer with a suitable thickness of a few nanometers, anode modification enables engineering of the interface electronic properties. The above results indicate that conventional dual-layer OLEDs of ITO/NPB/Alq3/cathode have an inherent weakness of instability that can be improved by the insertion of an ultrathin interlayer between ITO and HTL. The improvements are attributed to an improved ITO-HTL interfacial quality and a more balanced hole electron current that enhances the OLED performance. 

Table 5.2 Related studies of anode modification with conductive polymers in MFCs (P.D. power density. C.D. current density). a s-... 

Kim S, Hayashi K, Kitano Y, Tada M, Chiba K (2002) Anodic modification of proline derivatives using a lithium perchlorate/nitromethane electrolyte solution. Org Lett 4 3735-3737... 

Enhanced performance was also reported for anode modification with conductive polymers. A commonly used conductive polymer, polyaniline, can increase the current densities of MFC anodes. But it is also susceptible to microbial attack and degradation [39]. Schroder et al. [18] reported that a platinum electrode covered with polyaniline achieved a current density up to l.SmAcm in an MFC. Modification of polyaniline can improve its performance and stability, such as fluorinated PANI [40], PANI/carbon nanotube (CNT) composite [41], and PANI/titanium dioxide composite [42]. 

MFC efficiency MFC efficiency after anode before anode modification modification Ref. 

Several classes of interfacial material have been used for anode modification in the inverted cells. Thermally evaporated metal oxides, such as Mo03, NiO and are efficient materials that can... 

Anode performance Add redox mediators in anode chamber Use anode materials of high conductivity, good microbial compatibility and large surface area Anode modification with conductive polymers, metal oxides, etc. 

Methods for Anode Modifications and the Improvements in Performance of MFCs... 

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