Fabrication of carbon paste electrode containing [PFeW₁₁O₃₉]^4- polyoxoanion supported on modified amorphous silica gel and its electrocatalytic activity for H₂O₂ reduction

[PFeW₁₁O₃₉]^4- (PFeW₁₁) supported on the surface of 3-aminopropyl(triethoxy)silane modified silica gel was synthesized and used as a bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The electrochemical behavior of the modified electrode was investigated. Cyclic voltammetry studies showed that the PFeW₁₁ on the electrode surface sustained the same electrochemical properties as that of the PFeW₁₁ in solution. The preparation of chemically modified electrode is simple and quiet reproducible using inexpensive material. The modified electrode had high electrocatalytic activity toward H₂O₂ reduction and it was successfully applied as an electrochemical detector to monitor H₂O₂ in flow injection analysis (FIA). The electrocatalytic peak current was found to be linear with the H₂O₂ concentration in the range 10-200 μmol L^-1 with a correlation coefficient of 0.998 and a detection limit (3σ) of 7.4 μmol L^-1 H₂O₂. The electrode has the remarkable advantage of surface renewal owing to bulk modification, as well as simple preparation, good mechanical and chemical stability and reproducibility.