Redox behaviours and electrocatalytic properties of copper within Dawson structure-derived sandwich heteropolyanions [CU4(H2O)2(X2W15O56)2]16- (X=P or As)

Two Cu2+ sandwich-type heteropolyanions with the Dawson Moiety [X2X15O56](12-) (X = P or As) were synthesized. Their oxidized forms are stable from pH 3 to at least pH 7. Their characterization by cyclic voltammetry revealed the stepwise reduction of Cu2+ centers within these heteropolyanions before deposition of Cu-0 on the glassy carbon electrode surface. The presence of chloride ions in the supporting electrolyte does not induce the extraction of the copper centers from the heteropolyanions. These sandwich-type complexes are shown to have electrocatalytic properties towards the reductions of nitrate, nitrite, dioxygen and hydrogen peroxide. Electrochemical characterization of these complexes is offered for the first time. (C) 2003 Elsevier B.V. All rights reserved.