Electrochemical activity of rhodium complexes supported on fibrous-carbon material

The redox properties of heterogenized Rh-I, Rh-II, and Rh-III complexes wit h different, particularly organophosphorus, ligands were studied by cyclic voltammetry (CVA). The support is a carbon-paste electrode based on a fibro us-carbon material and activated carbon. The electrochemical reduction of R h-III produces ph metal, which further catalyzes hydrogen evolution. After the reduction of water-soluble binuclear Rh-II complexes, the CVA curves ex hibit peaks of electrocatalytic hydrogen evolution and irreversible Rh-I -- > Rh-II oxidation. The Rh-II complexes with organophosphorus Ligands are ch aracterized only by the peak of Rh-I --> Rh-II oxidation, After reduction, the Rh-I complexes behave as a pseudo-reverse Rh-0/Rh-I pair. The electron- donating properties of the ligand determine the reversibility of the system . The degree of structurization of the carbon matrix and the presence of ph osphorus(v) atoms in it affect the electrochemical activity of the Rh-II an d Rh-I complexes.