ELECTROCHEMICAL STUDY OF SOME RHODIUM COMPOUNDS AT A CARBON-PASTE ELECTRODE WITH ELECTROLYTIC BINDER

We have used the carbon paste electrode to study some rhodium compounds in various media. The oxidation of Rh(0) led to the formation of two different types of the Rh(III) complex in 6 M HCl, while the reduction of RhCl. 3H2O was found to take place at about the same potential that the reduction of H+ occurs. The reduction of Rh(III) in 1 M KCl and in 1 M KCl plus 20% ethanol led to Rh(0) and it took place, respectively, at -285 and -330 mV. On the contrary, the reduction of Rh(III) was found to lead to Rh(I) in the presence of triphenylphosphine and in 1 M KCl with 20% ethanol. The reduction of Rh(III) in a mixture of 1 M KCl and 1 M pyridine would most probably lead to a mixture of Rh(I) and Rh(II) and the reaction was reversible.