Bilayer platinum and copper hexacyanoferrate hybrid films have been prepared using repetitive cyclic voltammetry (CV). The deposition process and the films' electrocatalytic properties have been investigated. The electrochemical quartz crystal microbalance and CV were used to study the deposition and growth mechanism of the copper hexacyanoferrate film and platinum/copper hexacyanoferrate hybrid films. Scanning electron microscopy was used to study the surface morphology of the film. In the platinum/copper hexacyanoferrate hybrid films, the peak potentials of the platinum component that demonstrates a proton effect in acidic aqueous solution as the redox couple attributed to copper hexacyanoferrate was found to be cation dependent but not pH dependent. The electrocatalytic reactions of NH2OH, N2H4, and S2O32- were carried out using the platinum/copper hexacyano-ferrate hybrid films. (c) 2007 The Electrochemical Society.