Square wave voltammetry restructuring of platinum nanoparticle at boron doped diamond electrode for enhanced ammonia oxidation

Abstract

The ammonia oxidation reaction has been a topic of interest due to its possible use as a fuel in alkaline fuel cell systems. This may play a role on wastewater treatment for a stand-alone purification device. Nevertheless, the oxidation of ammonia is a complex surface process that needs catalyst development and synthesis. The Pt (100) facet has shown to be the most active catalyst surface and tailored synthesis of Pt nanocubes has been presented. An effort has been developed to transform Pt nanoparticles to nanocubes by square wave voltammetry at boron doped diamond electrodes. It is an electrochemical route for the synthesis of shape control platinum particles. During square wave voltammetry, a periodic oxidation and reduction of platinum occurs at the surface of the boron doped diamond electrode. The parameters and electrolytes used during this treatment determine the final platinum nanoparticle structure. In this work, platinum structure previously electrodeposited on boron doped diamond electrodes were modified using square wave voltammetry in ascorbic acid and acetone in a sulfuric acid solution, respectively, as electrolyte during the treatment. Three duration time of square wave voltammetry were used. The Pt nanoparticle modified boron doped diamond electrodes were characterized by cyclic voltammetry, scanning electron microscopy and were tested for the ammonia oxidation reaction. Nanoparticles were restructured to nanocubes by 10min of square wave voltammetry treatment in ascorbic acid solution. The peak current densities for the ammonia oxidation reaction increased ca. 80%, 15% and 20% for 30, 15, and 10min treatments, respectively. On the other hand, different platinum nanostructures were generated using acetone during square wave voltammetry treatment.