Bipolar electrochemistry

It is noteworthy that Ru(bpy)3 immobilization on the electrode surface facilitates the enhancement in the ECL intensity [134]. Ru(bpy)3 immobilized on an electrode surface comprising sol-gel-derived titania, and Nation was used for the determination of erythromycin in human urine sample. ECL combined with bipolar electrochemistry has been used for various analytical purposes by Crooks [66, 135-137] and Manz s co-workers [17]. Manz employed ECL with bipolar electrode for the detection of amines and Crooks and co-workers for the detection of FefCN) , Ru(NH3)i, benzyl viologen, and various ananlytes. Recently, bipolar electrochemistry has also been coupled to ECL in order to propel light-emitting bipolar electrochemical swimmers Fig. 5.22. In this approach, synergestic action... 

The Construction of Circuitry Using Spatially Coupled Bipolar Electrochemistry... 

The formation of electrical contacts between metal structures and devices is an integral aspect of circuit construction at all scales of commercial importance. Currently photolithographic, screen printing and microsoldering techniques are the methods of choice to establish connections. However, these approaches require masks, templates or intimate physical contact with the components. Spatially Coupled Bipolar Electrochemistry (SCBE) is a novel technique which makes use of electric fields to create electrical connections between components, which not only avoids physical contact but is also applicable in principle to the formation of three dimensional circuitry. The SCBE technique has been developed to a point where the construction of functional robust circuits has been achieved. Preliminary data demonstrating the application of this approach to the formation of polypyrrole bridges between isolated gold structures is also presented. 

Bipolar electrochemistry " is the term used to describe this process since the particle serves as both anode and cathode. This phenomenon has been investigated using fluidized or packed bed electrodes for applications in metal recovery , electrosynthesis " and ultramicroelectrode " studies. 

Bipolar electrochemistry requires a medium of sufficiently low conductivity to avoid excessive parasitic current leakage at the feeder electrodes. In this regard the bipolar electropolymerization of conductive polymers appears to be an attractive additional method to create interconnects between isolated metal components because the neutral monomer does not significantly contribute to conductivity and can thus be introduced in relatively high concentrations. Furthermore, as opposed to the examples of SCBE described above using copper structures, it is not necessary for the metal component to electrodissolve to create an interconnect. 

A recent review of bipolar electrochemistry focuses on the basic principles of controlling solution, rather than electrode potentials, and includes many demonstrated and possible applications [12]. The potential gradient generated across the bulk solution covering the electrode arrays controls the anode-to-cathode potential difference, which drives electrochemical reactions to generate optically detectable anodic products. Various wireless bipolar electrode array configurations and applications are considered. 

Fosdick SE, Knust KN, Scida K, Crooks RM (2013) Bipolar electrochemistry. Angew Chem Int Ed 52 10438-10453... 

It has been recently found that direct electrical contact, via a metal wire, to the catalyst-electrode is not necessary to induce the effect of electrochemical promotion.8 11 It was found that it suffices to apply the potential, or current, between two terminal electrodes which may, or may not, be catalytically active. The concept appears to be very similar with that of the bipolar design used now routinely in aqueous electrochemistry. 

As in aqueous electrochemistry it appears that application of a potential between the two terminal (Au) electrodes leads to charge separation on the Pt film so that half of it is charged positively and half negatively8 thus establishing two individual galvanic cells. The Pt film becomes a bipolar electrode and half of it is polarized anodically while the other half is polarized cathodically. The fact that p is smaller (roughly half) than that obtained upon anodic polarization in a classical electrochemical promotion experiment can be then easily explained. 

Licht S, Khaselev O, Ramakrishnan PA, Soga T, Umeno M (1998) Multiple-bandgap photoelectrochemistry Bipolar semiconductor ohmic regenerative electrochemistry. J Phys Chem B 102 2536-2545... 

Aqueous, alkaline fuel cells, as used by NASA for supplemental power in spacecraft, are intolerant to C02 in the oxidant. The strongly alkaline electrolyte acts as an efficient scrubber for any C02, even down to the ppm level, but the resultant carbonate alters the performance unacceptably. This behavior was recognized as early as the mid 1960 s as a way to control space cabin C02 levels and recover and recycle the chemically bound oxygen. While these devices had been built and operated at bench scale before 1970, the first comprehensive analysis of their electrochemistry was put forth in a series of papers in 1974 [27]. The system comprises a bipolar array of fuel cells through whose cathode chamber COz-containing air is passed. The electrolyte, aqueous Cs2C03, is immobilized in a thin (0.25 0.75 mm) membrane. The electrodes are nickel-based fuel cell electrodes, designed to be hydrophobic with PTFE. 

Gillery, B., Bailly, M., and Bar, D. 2002. Bipolar membrane electrodialysis The time has finally come. In Proceedings of 16th International Forum on Applied Electrochemistry Cleaner Technology—Challenges and Solutions. Amelia Island Plantation (FL, USA) November 10-14 (online publication htpp //ameridia.con.htmEebc.html). 

Licht S., Khaselev 0., Ramakrishnan P. A., Soga T. and Umeno M. (1998b), Multiple-bandgap photoelectrochemistry bipolar semiconductor ohmic regenerative electrochemistry , J. Phys. Chem. 102, 2536-2545. 

PM-IRRAS data have been reported using both dispersive [86, 87] and FTIR spectrometers [88-90]. One of the earhest applications in electrochemistry was reported by Russell and coworkers [87], who employed the technique to substantiate the theory that the bipolar band observed by Beden and coworkers [71] in their EMIRS experiment on the electro-oxidation of methanol was due to Pt—G=0 shifting its frequency as the potential was altered. The absolute spectra obtained by the authors clearly showed the monopolar Pt—C=0 feature increasing in frequency as the potential of the Pt electrode was increased (Fig. 5). 

Fleischmann, M. and Ibrisagic, Z. (1980) Electrochemical measurements in bipolar trickle tower reactors. Journal of Applied Electrochemistry, 10, 151. 

Fleischmann, M., Ghoroghchian, J. and Jansson, R.E.W. (1981) Reduction of 2-nitropropane in an undivided, flooded bipolar cell. Journal of Applied Electrochemistry, 11, 55. 

It is carried out in an undivided cell developed by BASF the capillary gap cell [19] (Fig. 2). This cell contains a stack of bipolar round graphite electrodes. The electrodes with a central hole are separated by spacers and connected in series. The electrolyte flows through the middle channel which is generated by the stacking and outwards between the electrodes. By this stacking the capillary gap cell is one answer to the permanent question in electrochemistry on how to realize sufficient electrode area in as little space as possible, respectively, in one cell. 

Table 22.8 Acid uptake (sum of cathode and anode) of different bipolar plate materials at the EoL relative to the phosphoric acid content of the system at the BoL [93], with permission of International Electrochemistry Society...

Davies, D.P., P.L. Adcock, M. Turpin et al. 2000. Bipolar plate materials for solid polymer fuel cells. Journal of Applied Electrochemistry 30 101-105. 

Figures 7 and 8 illustrate the results of a coating benchmark, which shows clear differences in performance and durability, which depend on the coating technique and composition. With different coatings the conductivity and durability of the metallic bipolar plate exceed the properties of a composite plate with comparable flow field. Diverse low-cost coatings (RNZ 05-06, RNZ 05-12, RNZ 05-13, and RNZ 05-16), which differ mainly in their canposition, highlight the necessity to control the chemistry and electrochemistry of the complete system of plate and coating. It was shown that with optimized coating composition (RNZ 05-16) it is possible to approximate the performance and durability of the gold-coated reference plate.

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