Entrapment of the Complex Cu(2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane) in Sol-gel Electrodes for Electrocatalysis

Ariela Burg, Chemical Engineering Department, SCE – Shamoon College of Engineering, Beer-Sheva, Israel
Inbar Elias, Chemistry Department, Ben-gurion University Of The Negev, Beer-sheva, Israel
Dror Shamir, Nuclear Research Centre Negev, Beer-sheva, Israel
Lina Apelbaum, R&d, Makhteshim Chemical Works Ltd, Beer-sheva, Israel
Yael Albo, Chemical Engineering , Ariel University, Ariel, Israel
Dan Meyerstein, Chemistry, Ben-gurion University Of The Negev, Biological Chemistry, Ariel University, Israel

Heterogeneous catalysis offers a number of advantages, including the possibility of recycling the catalyst. Cu^II(2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane) complex was entrapped in sol-gel matrix electrodes and the activity of the copper complex as an electro-catalyst was studied. Copper complexes, and Cu(I) complexes in particular, are known as catalysts of a variety of homogeneous processes. However, little is known about the mechanism of their activity in heterogeneous systems. The electro-catalytic activity of the Cu(2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane) complex, was studied in the de-chlorination reaction of tri-chloro-acetic acid (TCA). The effects of pH and substrate concentration were studied using cyclic voltammetry at different scan rates and product analysis. The results points out that: 1. The (CuL) complex is an electro-catalyst for the reduction of TCA both in homogenous and heterogeneous systems. 2. The pH of the solution in the heterogeneous electrochemical process does not affect the electro-catalytic properties of the complex in the electrodes. Plausibly the pH of the solution does not change the structure of the complex when it is entrapped in the electrode. 3. The catalyst can be recycled and used in a large number of recycles, even after changes in the substrate concentration and the pH. 4. An important and general conclusion is that the nature of the sol-gel matrix, as determined by using different precursors, affects dramatically the rate of the electro-catalytic process.

Based on the nature of the final products a tentative mechanism of the electro-catalytic process is proposed.