Preparation, electrochemical behavior and performance of gallium hexacyanoferrate as electrocatalyst of H2O2

The gallium hexacyanoferrate (GaHCF) was synthesized chemically and characterized by FTIR technique. Its electrochemical behavior was carefully investigated by fabricating a GaHCF modified carbon paste electrode in various supporting electrolyte. The experimental results showed that in KNO3, K2SO4, KCl and other supporting electrolyte, GaHCF yielded one pair of ill-defined redox waves with a formal potential of 0.9 V (versus SCE). In 0.050 mol L-1 phosphate buffer solution (PBS, pH 6.8), however, GaHCF yielded one pair of well-defined redox peaks with a formal potential of 0.222 V. Furthermore, this modified electrode exhibited a high electrocatalytic activity toward the reduction of H2O2 in pH 6.8 PBS, with over-potential dramatically lower than that of on the bare carbon paste electrode. Amperometry was used for the determination of H2O2, under the optimal conditions, a linear dependence of the catalytic current versus H2O2 concentration was obtained in the range of 4.9 x 10(-6) to 4.0 x 10(-4) mol L-1 with a detection limit of 1 x 10(-6) mol L-1 when the signal-to-noise ratio was 3, and a sensitivity of 27.9 mu A mM(-1) (correlation coefficient of 0.997). Chronoamperometry was used to conveniently determine the diffusion coefficient of H2O2 in the solution. (c) 2007 Elsevier Ltd. All rights reserved.