A monolayer of Keggin-type heteropolyanion [SiNi(H2O)W11O19](6-) was fabricated by electrodepositing [SiNi(H2O)W11O39](6-) on cysteamine modified gold electrode. The monolayer of [SiNi(H2O)W11O39](6-) modified gold electrode was characterized by atomic force microscopy (AFM) and electrochemical method. AFM results showed the [SiNi(H2O)W11O39](6-) uniformly deposited on the electrode Surface arid formed a porous monolayer. Cyclic voltammetry exhibited one oxidation peak arid two reduction peaks in 1.0 M H2SO4 in the potential range of -0.2 to 0.7 V. The constructed electrode Could exist in a large pH (0-7.6) range and showed good catalytic activity towards the reduction of bromate anion (BrO3-) and nitrite (NO2-), arid oxidation of ascorbic acid (AA) in acidic solution. The well catalytic active of the electrode was ascribed to the porous structure of the [SiNi(H2O)W11O39](6-) monolayer. (c) 2008 Elsevier Ltd. All rights reserved.