Preparation of 100−160-nm-Sized Branched Palladium Islands with Enhanced Electrocatalytic Properties on HOPG

A method for the preparation of stable 100−160-nm-sized quasi-2D branched palladium islands on highly oriented pyrolitic graphite (HOPG) is described. This type of island is electrodeposited from an aqueous acidic palladium chloride solution containing an excess of sodium perchlorate at potentials just a few millivolts above the threshold potential of the hydrogen evolution reaction. Each branched palladium island consists of a central 3D core and large quasi-2D branches that form a dense radial pattern. In contrast to massive palladium, branched islands exhibit enhanced electrocatalytic properties for the hydrogen atom electroadsorption/electrodesorption reaction and the electrooxidation reaction of hydrazine. This enhancement is mainly related to the fractal characteristics of branched palladium islands on HOPG.