Electrochemical Dynamics of a Single Platinum Nanoparticle Collision Event for the Hydrogen Evolution Reaction

Abstract

Chronoamperometry was used to study the dynamics of Pt nanoparticle (NP) collision with an inert ultramicroelectrode via electrocatalytic amplification (ECA) in the hydrogen evolution reaction. ECA and dynamic light scattering (DLS) results reveal that the NP colloid remains stable only at low proton concentrations (1.0 mm) under a helium (He) atmosphere, ensuring that the collision events occur at genuinely single NP level. Amperometry of single NP collisions under a He atmosphere shows that each discrete current profile of the collision event evolves from spike to staircase at more negative potentials, while a staircase response is observed at all of the applied potentials under hydrogen-containing atmospheres. The particle size distribution estimated from the diffusion-controlled current in He agrees well with electron microscopy and DLS observations. These results shed light on the interfacial dynamics of the single nanoparticle collision electrochemistry.

Collision Incidents of Single Tetrahexahedral Platinum Nanocrystals Recorded by a Carbon Nanoelectrode

“…The current “steps” were 25 pA for the first fluctuation and 7 pA for the second current fluctuation (Figure ), which can be ignored as background, indicating the departure of the THH Pt NC from the carbon nanoelectrode. However, the experimental current kept decreasing during the whole persistence time, indicating that there was serious passivation process of the THH Pt NC during the collision incident. We don't have any direct evidence yet to elucidate why the passivation happens.…”

Detection of Transient Nanoparticle Collision Events Using Electrochemiluminescence on a Closed Bipolar Microelectrode

“…Due to the particle's short transit time in the bulk redox solution (from <1 ms to a few ms), particle aggregation is largely avoided, leading to a reproducible HER current signal while using concentrated bulk acid conditions. This contrasts the classical diffusion‐limited methods whereby aggregation is observed for citrate‐capped nanoparticles in ionic concentrations higher than ∼20 mM or a lower pH than 3.13 (p K a of the citrate capping ligand) . By increasing the bulk acid concentration in the microjet system, we correspondingly increase the magnitude of the electrocatalytically amplified signal to generate a more easily detectable transient event consisting of a sharp current spike and a transient current decay.…”

Single Particle Electrochemistry of Collision

“…In comparison, the current signals remained staircase‐like at all potentials in H 2 ‐saturated solution while the magnitude of the current value was much lower than expected (Figure c). It was the absorption of H 2 in the crystal lattice of Pt NPs that contributed to the passivation of the HER electrocatalyst with the observed decrease of current values …”

“…b,c) Represent the amperometric i – t curves after collision experiments at different potentials in He‐saturated solution and H 2 ‐saturated solution, respectively. All panels reproduced with permission . Copyright 2018, Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim.…”