ELECTROCHEMICAL BEHAVIOR OF H3PW12O40/ACID-ACTIVATED BENTONITE POWDERS

Electrochemical behavior of 12-tungstophosphoric acid (HPW)/acid-activated bentonite (AAB) powders with various loadings of HPW was investigated. The physicochemical properties of the prepared powders were examined by X-ray powder diffraction, nitrogen adsorption-desorption isotherms, atomic force microscopy and cyclic voltammetry measurements. The results indicated that the prepared powders are composed mainly of oriented domains of large rock blocks, probably resulting from a preferable deposition of bentonite particles having a face-to-face interaction. The particles had a mainly disordered mesoporous structure with a pore volume that varied according to the pore size in the range of 2-50 nm. In addition, the particles had crystallite size between 4.9 and 9.0 nm. The electrocatalytic activities of prepared HPW/AAB electrodes were studied in the oxidation of NO2- and the results revealed that the electrodes possessed relatively higher nitrite oxidation currents than AAB electrode. The best electroactivity was observed for HPW3/AAB electrode (AAB + + 20 wt % HPW) and the limit of detection (3 sigma) was determined as 8 mu M.