Electrosynthesis of palladium nanocatalysts using single droplet reactors and catalytic activity for formic acid oxidation

The synthesis of nanosized palladium (Pd) catalyst from a Pd²⁺ emulsion is performed using the emulsion nanodroplet-mediated electrodeposition method. In this method, aqueous emulsion droplets act as tiny reactors for the inner precursor (e.g., Pd²⁺) to reduce and generate the corresponding metal products while they are discretely colliding on the working ultramicroelectrode surface, which is biased at a suitable constant potential. The utilized volume of each reactor (with a given concentration of the Pd²⁺ precursor) and the monitored total number of deposition (i.e., droplet collision) events, being the critical factors, can facilitate the controllable (or quantifiable) synthesis of Pd nanocatalysts where the amount of Pd per deposition event and the generated product amount are determinable. In this research, individual Pd nanocatalysts nucleate from droplet collisions and become uniformly distributed on the substrate surface. The electrocatalytic activities of the synthesized Pd nanocatalysts for formic acid electrooxidation are higher than ca. 10 A mg_(Pd)⁻¹.