Electrocatalytic reduction of nitrite on the surface of a glassy carbon electrode modified by palladium(II)-substituted Dawson type heptadecatungstodiphosphate

A palladium(II)-substituted Dawson type heptadecatungstodiphosphate, K-8[P2 W17O61Pd(H2O)](abbreviated as P2W17Pd in the following), was used to constr uct a new kind of chemically modified electrode (CME) by electrodeposition on the surface of a glassy carbon electrode for the first time. This modifi ed electrode was characterized by Fourier transform infrared reflection abs orption spectroscopy (FTIRRAS), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). FTIRRAS and XPS suggested that the adsorbed specie s on the electrode surface has the same Dawson type structure as the hetero polyanion in buffer solution. A couple of waves was observed on the P2W17Pd CME, which was ascribed to the redox process of the palladium center in th e heteropolytungstate. After continuous potential scanning for 30 min in a pH 4.0 buffer, 94% of the original coverage remains for the CME. The P2W17P d CME had high electrocatalytic activity for nitrite reduction and exhibite d good reproducibility and stability. The catalytic peak current was found to be linear with the nitrite concentration in the range of 1 similar to 50 mmol/L, with a correlation coefficient of 0.994. The effect of solution pH on the catalytic activity of the CME for nitrite reduction was also invest igated.