Electrochemically assisted

A novel, electrochemically assisted method of obtaining semiconductor quantum dots supported on a surface has been introduced by Penner and his group [123], It comprised a hybrid electrochemical/chemical (E/C) process consisting of electrochemical deposition followed by chemical modification and it was described as a general, rapid, and low-cost solution-phase method for synthesizing supported Q-dots of metal salts. 

Tian J-H, Yang Y, Zhou X-S, Schollhom B, Maisonhaute E, Chen Z-B, Yang F-Z, Chen Y, Amatore C, Mao B-W, Tian Z-Q (2010) Electrochemically assisted fabrication of metal atomic wires and molecular junctions by MCBJ and STM-BJ methods. ChemPhysChem 11 (13) 2745-2755... 

P.V. Kamat, Electrochemically assisted photocatalysis titania particulate film electrodes for photocatalytic degradation of 4-chlorophenol, J. Phys. Chem. 97 (1993) 9040-9044. 

The use of Fe, indium, and zinc as sacrificial anodes in the electrochemically assisted Reformatsky reaction of ethyl 2-bromoalkanoates with succinic anhydride is found to be effective, giving l-ethyl-3-oxohexanedioates in 49 80%... 

Carr, R., Feng, J., Kolodsick, K., Wang, D., Zhong, M., Holliman, C., and Kingsmill, C. A. (2006). Electrochemical assisted electrospray ionization tandem mass spectrometry Improving the detection limit of electrochemically active species. Poster presented at 54th ASMS Conference on Mass Spectrometry and Allied Topics, Seattle, WA. 

Jurva, U., Wikstrom, H. V., and Bruins, A. P. (2002). Electrochemically assisted Fenton reaction Reaction of hydroxyl radicals with xenobiotics followed by on-line analysis with high-performance liquid chromatography/tandem mass spectrometry. Rapid Commun. Mass Spectrom. 16 1934-1940. 

Ht is claimed (Gleason, Fox, 1998) that electrochemically assisted nuclear reactions cause a 99% remediation of thorium to nonradioactive products. Should it be possible to apply such processes more widely, an improved solution to the waste problem may have been found. 

In a single-crystal semiconductor (n-type) based photoelectrochemical cell, the problem of achieving charge separation is easily overcome by applying an anodic bias as was first demonstrated by Honda and Fujishima [263]. Using a single crystal Ti02, they were able to carry out the photoelectrolysis of water under the influence of an anodic bias. This concept to manipulate the photocatalytic reaction by electrochemical method can be extended to nanostructured semiconductor thin films [39,116]. The principle of electrochemically assisted photocatalysis is illustrated in Fig. 10. 

Figure 11 The absorption spectrum of a 0.2-mM NBB dye solution recorded at different time intervals following electrochemically assisted photocatalysis. An immobilized Ti02 particulate film cast on a conducting glass electrode was maintained at an electrochemical bias of 0.8 V SCE during the photocatalytic degradation experiment. (From Ref. 265.)...

Vinodgopal, K. Stafford, U. Gray, K. A. Kamat, P. V. Electrochemically assisted photocatalysis. II. The role of oxygen and reaction intermediates in the degradation of 4-chlorophenol on immobilized Ti02 particles, J. Phys. Chem 1994, 98, 6797. 

In addition, there are several important chemical processes in electrochemically assisted coagulation. The more important is the chemical dissolution which consists of the oxidation of the metal sheets with the simultaneous reduction of water to form hydrogen. This process is represented by (4.52). 

Oturan, M.A., Oturan, N., Lahitte, C. and Trevin, S. (2001) Production of hydroxyl radicals by electrochemically assisted Fenton s reagent Application to the mineralization of an organic micropollutant, pentachlorophenol. J. Electroanal. Chem. 507,96-102. 

McMurray, T. A., Byrne, J. A., Dunlop, P. S. M. and McAdams, E. T. (2005). Photocatalytic and electrochemically assisted photocatalytic oxidation of formic acid on Ti02 films under UVA and UVB irradiation. J. Appl. Electrochem. 35(7-8), 723-731. 

Vinodgopal, K. and Kamat, P. V. (1995). Electrochemically assisted photocatalysis using nanocrystalline semiconductor thin-films. Solar Energy Mater. Solar Cells 38(1 4), 401 410. 

Liu, H., Grot, S., and Logan, B. E. 2005. Electrochemically assisted microbial production of hydrogen from acetate. Environ. Sci. Technol. 39, 4317-4320. 

B) Electrochemically-assisted photocatalysis As discussed above, photocatalytic processes are electrochemical in nature. A clever enhancement approach involves the application of a judiciously selected potential bias to a semiconductor electrode. The potential promotes a better charge-separation, thus decreasing the electron-hole recombination and increasing the yield of the target processes. This approach is called electrochemically... 

The relationship between electrochemical items and materials science can be grouped according to three main aspects as shown in Figure 1.1. It should be noted that electrosynthetic methods allow for preparing a variety of materials, from porous oxide layers in metal anodes, to MOFs (Mueller et al., 2006), layered double hydroxides (LDHs Yarger et al., 2008), and porous carbons (Kavan et al., 2004). Furthermore, porous materials can be modified, functionalized, or hybridized (yide infra) via electrochemically assisted procedures, thus resulting in the preparation of novel materials. 

In contact with aqueous alkaline media, metal oxide electrochemistry is dominated by hydroxylation processes. However, in contact with acidic media, proton and cation insertion processes occur, eventually leading to complicated responses where reductive or oxidative dissolution processes frequently take place (Scholz and Meyer, 1998 Grygar et al., 2002 Scholz et al., 2005). As far as such processes involve disintegration of the porous structure of the material, electrochemically assisted dissolution processes will be taken only tangentially here. 

Perhaps the most important synthesis parameter affecting the crystallization of pyrochlore from alkaline solution is the oxidizing potential within the reaction medium. It is observed that this parameter has dramatic effects on both crystallinity and extent of ruthenium substitution by Pb . For example, a synthesis in which O2 is bubbled into the reaction medium will yield a well crystallized pyrochlore 2-3 times faster than a synthesis where O2 sparging is not provided. Crystalline pyrochlores cannot be obtained under any synthesis conditions (except those that are electrochemically assisted) when N2 sparging is used. The necessity for relatively oxidizing conditions in order to yield crystalline expanded pyrochlores is consistent with the hypothesis that these pyrochlores do... 

M. Sterner, N. Roxhed, G. Stemme, J. Oberhammer, Electrochemically assisted maskless selective removal of metal layers for three-dimensional micromachined SOI RE MEMS transmission lines and devices, J. Microelectromech. Syst. 20 (4) (2011) 899-907. 

Downard AJ (2000) Electrochemically assisted covalent modification of carbon electrodes. Electroanalysis 12 1085-1096. 

---