Preparation of nano- and microstructured gold surfaces by application of a square wave potential regime

Gold nanometallic structures have been prepared by application of square wave potential regime to a platinum electrode in a 1.0 × 10^?3 M HAuCl₄ + 0.5 M H₂SO₄ solution. Formation of gold particles onto the platinum surface has been followed by cyclic voltammetry, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The results indicate that the size, shape, uniformity of distribution of the particles are affected by the selected parameters of the applied square wave potential regime. Parameters of the square wave include the frequency, the lower and the upper limits of the square wave and the time of application of the square wave potential regime. The concentration of HAuCl₄ in the solution is another important factor. The results of the present work indicated that the 100 Hz frequency is the optimal frequency for obtaining gold nanoparticles on platinum surface. Deposition time has been also found to play a critical role in affecting the size, shape and homogeneity of gold nanostructures at the surface. The surface coverage with nanoparticles as calculated from the decrease in the charge of hydrogen adsorption/desorption peaks is found to be directly proportional to the time of application of the square wave. Testing the nanostructured gold/Pt electrode for oxidation of formic acid shows its higher catalytic activity than that of platinum and gold plain electrodes.