Electrochemical behavior of vanadium-substituted Keggin-type polyoxometalates in aqueous solution

摘要

Cyclic voltammetry was carried out on selected vanadium-substituted Keggin polyoxometalates in aqueous solution with a focus on K_3H_2[α-SiVW_(11)O_(40)] _ 6H_2O (SiVW_(11)O_(40)) and K_4H_2[γ(1, 2)-SiV_2W_(10)O_(40)]_ 4H_2O (SiV_2W_(10)O_(40)). The redox waves of the V-O and W-O framework for both polyanions are pH- and scan rate-dependent. The first vanadium-centered wave (V-wave) for SiVW_(11)O_(40) shows a classical potential shift as a function of acidity at pH < 3.5, and then becomes pH-independent above this value. Above pH 3.5, the W-centers in SiVW_(11)O_(40) and SiV_2W_(10)O_(40) exhibit efficient electrocata_lytic activity towards the reduction of nitrite and hydrogen peroxide while the V-waves also exhibit an electrocatalytic response in nitrite-containing solutions.