Electrochemical characterization of the encapsulated polyoxometalates (POMs) into the zeolite

The electrochemical characterization of polyoxometalates encapsulated into the zeolite (POM@Z) is presented for the first time. A stable film comprising POM@Z and graphite powder was prepared on glassy carbon electrode (POM@Z-GCE) by dip-coating. The cyclic voltammograms of the modified electrode showed three well-defined pairs of redox peaks due to the redox reaction of the encapsulated POMs. The values of charge transfer coefficient (α) and the heterogeneous charge transfer rate constant (kapp) for three pairs of redox peaks were evaluated. The electrochemical studies revealed that the encapsulated POMs show very slower electrochemical responses than those of un-encapsulated POMs arising from the restraint in the zeolite pores towards diffusion of charge-balancing electrolytes. According to the obtained evidences an intra-zeolite charge transfer mechanism for the encapsulated POMs can be concluded. The POM@Z-GCE showed the advantages of excellent electrocatalytic activity towards reduction of H2O2.