Single Pt Nanoparticle Impact Studies of Hydrogen Evolution on Si Photocathodes

Nanoparticle electrocatalysts are widely used for the production of renewable fuels, energy storage devices, and chemical sensors. Over the past ten years, analysis of single nanoparticle electrochemical events has emerged as a powerful tool for characterizing and understanding the inherent heterogeneity of synthesized nanoparticles. One of the long-term goals of this area of research is to understand and quantify the electrocatalytic behavior of nanoparticles at the single entity level. Here, we present a study of HER at the single nanoparticle level by monitoring stochastic collisions between Pt NPs and a substrate electrode. The experimental setup uses a small diameter microcapillary (≈1.3 µm) that is filled with a solution containing 1 mM HClO4 and Pt NPs and placed in contact with a semiconducting electrode, creating an electrochemical cell. We observe individual nanoparticle collisions and their current “blips” or “steps” which is an indication of the particle hitting the semiconductor or sticking to its surface when -300mV to -600mV are applied to the system. Although significant barriers exist in correlating a specific nanoparticle impact to a specific particle, important information such as the spike height, nanoparticle dwell time, and multi-peak impacts are studied and used to understand the physical and chemical environment of the particle during electrocatalysis. This study of HER highlights the inherent variability in populations of nanoparticle electrocatalysts and enable a better understanding to the nanoscale electrocatalytic properties which are most effective for the reaction.