The study of monochlorinated phenols using hyphenated electrochemical method

2011 ◽  
Vol 76 (8) ◽  
pp. 997-1012
Author(s):  
Matilda Roziková ◽  
Pavel Janderka ◽  
Libuše Trnková
Keyword(s):  
Electrode Surface ◽  
Electrochemical Method ◽  
Quartz Crystal ◽  
Film Formation ◽  
Electrochemical Quartz Crystal Microbalance ◽  
Polymeric Film ◽  
Low Permeability ◽  
Pt Electrode ◽  
Cyclic Voltammetric ◽  
Strong Adsorption

Cyclic voltammetric (CV) study of electrooxidation of monochlorophenols (2-chlorophenol, 3-chlorophenol, 4-chlorophenol) on a Pt electrode in 0.5 M H2SO4 was combined with the experiment using electrochemical quartz crystal microbalance (EQCM). For all chlorophenols the polymeric film formation on the electrode surface has been observed and the electrode surface was completely covered with polymeric film after five cycles. Partial deactivation of the electrode resulting in the formation of the more permeable film was created in the case of 2-chlorophenol and the film of 4-chlorophenol was created also with the low permeability. The influence of the scan rate on the electrooxidation of chlorophenol was evaluated. It was found that the lower electropolymerization rate and better permeability of the film was observed at higher scan rates. Valuable insights into complex electrooxidation processes of all chlorophenols were also gained by means of the elimination voltammetry with linear scan (EVLS). The EVLS functions, eliminating two current components, reveal a strong adsorption state of 3-chlorophenol and show differences in electrochemical behavior of chlorophenols in all cycles. From the comparison of elimination results of corresponding derivatives the different mechanism of electrooxidation was suggested.

Selenium(IV) Electrochemistry on Silver: A Combined Electrochemical Quartz-Crystal Microbalance and Cyclic Voltammetric Investigation

2003 ◽  
Vol 68 (9) ◽  
pp. 1579-1595 ◽  
Author(s):  
Giovanni Pezzatini ◽  
Francesca Loglio ◽  
Massimo Innocenti ◽  
Maria Luisa Foresti
Keyword(s):  
Cyclic Voltammetry ◽  
Quartz Crystal Microbalance ◽  
Electrochemical Behavior ◽  
Quartz Crystal ◽  
Reduction Process ◽  
Electrochemical Quartz Crystal Microbalance ◽  
Potential Range ◽  
Cyclic Voltammetric ◽  
Scan Rate ◽  
Process Of Se

The electrochemical behavior of Se(IV) on silver was investigated by cyclic voltammetry and electrochemical quartz-crystal microbalance (EQCM) measurements. As already reported in the literature, Se(IV) electrochemistry is always complex, and on silver even more, due to the formation of a compound. Our results confirm that the reduction process of Se(IV) occurs through two reaction paths, Se(IV) → Se(0) and Se(IV) → Se(-II); the product Se(-II) then reacts with Se(IV) through a comproportionation reaction. The latter step leads to red Se that, according to the literature, is the only electroactive form of Se(0). The presence of the electroactive red Se is evident both in the negative range of potentials, through the reduction Se(0) → Se(-II), and in the less negative range of potentials, through the oxidation Se(0) → Se(IV). Moreover, our measurements pointed to the formation of a deposit that never redissolves. This deposit seems to be the electroinactive gray Se. The electrochemical behavior of Se(IV) was investigated in the whole potential range accessible on silver. Our results confirm the occurrence of competitive processes whose predominance depends on the scan rate, as well as on the potential limits of voltammetry. A detailed table with the processes occurring in different potential ranges was drawn up.

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