Ligand and electrolyte effects in the electroreduction of copper-substituted heteropolyanions

Focus is put on the electrochemical behaviours of the Cu2+ centre in several copper-substituted heteropolyanions. These behaviours are found to depend clearly on the structure and composition of the precursor lacunary oxometalates. In sulfate medium, complete demetallation is easily observed upon reduction. However, quantitative recovery of the complex is obtained by reoxidation. Therefore, after the deposition process, the lacunary heteropolyanions retain their original properties and can be used again to capture metal ions in solution. Various behaviours of the copper deposition process are observed depending on the presence of chloride in the supporting electrolyte.