Nanoparticle ensemble electrodes: fabrication by short-pulse sputtering and characterization by scanning probe microscopy and voltammetry

Abstract

Nanoparticle ensembles (NPEs) are useful platforms to study the electrocatalytic properties of nano-sized materials. A fabrication method that guarantees a good control over the morphological features, as well as a reliable characterization, are required for a proper analysis of electrochemical data measured on these electrodes. This work describes a simple, fast, and clean procedure for the fabrication of random arrays of Pt nanoparticles (NPs) supported on flat electrodes by sputtering of metal targets for short times. Besides, a strategy for morphological characterization of the ensembles based on a combination of scanning tunneling microscopy (STM) and voltammetric information is reported. The method permits to attain good control on the size and coverage of NPs in the ensemble through the sputtering parameters. Pt NPs sputtered on highly ordered pyrolytic graphite (HOPG) grow bidimensionally with heights in the range 0.8–1.2 nm, while the lateral diameters of NPs and the surface coverage are adjusted in the range 2–15 nm by controlling both the sputtering current and the sputtering time. The stability and electrochemical behavior for proton reduction under mixed control in acid media were evaluated on HOPG-supported Pt ensembles fabricated by the described method.