Hydrogen Evolution Reaction on a Single Platinum Atom

Single-atom electrocatalysts are typically reported on in bulk scale applications (i.e. as dispersions of many individual atoms across a macroscale electrode) which represents the electrochemical activity across all single-atom electrocatalysts at once. Less is known about the fundamental workings of individual single-atom electrocatalysts. To elucidate the electrochemical activity of a single atom, this thesis presents the isolation of the hydrogen evolution reaction at a single platinum atom deposited on an electrode surface. Two important techniques were employed during the experimental work to achieve measurements at the individual atom scale: scanning electrochemical cell microscopy, and collision electrochemistry. Scanning electrochemical cell microscopy enabled the physical downsizing of the working electrode to the nanometre scale, cutting down on the background noise. The collision electrochemistry approach enabled the controlled delivery of a single Pt⁴⁺ species to be reduced to Pt⁰ upon collision with the electrode. The presence of Pt at the electrode acts to catalyse the hydrogen evolution reaction, amplifying the current to produce peaks that indicate the Pt⁴⁺ collision event occurred. These peaks were analysed through calculating their frequency vs Pt⁴⁺ concentration, observing their height and width as a result of the applied potential, and obtaining the hydrogen evolution reaction steady state current at a single platinum atom. A discussion surrounding how the interactions and dynamics of the Pt⁴⁺ ion during the collision event impacts the shape of the current and peaks is presented.