Polyoxometalate/chitosan–electrochemically reduced graphene oxide as effective mediating systems for electrocatalytic reduction of persulfate

Heteropolymolybdate H4SiMo12O40 (SiMo12) and chitosan–electrochemically reduced graphene oxide (CS-ERGO) multilayer composite films have been processed on Indium tin oxide electrode (ITO) through electrochemical growth method. The use of CS favored the adsorption of negatively charged SiMo12 anions and thus facilitated the growth of the multilayered films. The presence of ERGO enhanced the area of conductive surface, which is beneficial for the increase of the coverage value of SiMo12 on the electrode. By combining these two materials, the loading of SiMo12 was significantly increased. Thus, the CS-ERGO/SiMo12 multilayer films provide more catalytically active centers, which results in a high level of catalytic activity towards the reduction of S2O82−. Results of scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry indicated the successful fabrication of CS-ERGO/SiMo12 multilayer film modified electrode. Application of the proposed electrode in electrochemical sensing was further demonstrated by electrocatalytic reduction of persulfate. Amperometry showed that the proposed sensor exhibited a linear detection range for S2O82− from 0.67 to 30.62 μM with excellent sensitivity of 0.0448 μA μM−1 and a low detection limit of 0.05 μM, which outperformed most previously reported electrochemical sensors. In addition, good anti-interference and stability was also demonstrated. These features make the new SiMo12 modified electrode an ideal substrate for S2O82− detection.