Simultaneous activity and surface area measurements on single mesoporous nanoparticle aggregates

Abstract

The underpotential deposition of hydrogen and the hydrogen evolution reaction is studied at individual mesoporous nanoparticles. This work shows how the electroactive surface area and catalytic activity of these individual particles can be simultaneously measured.

Nanoimpacts at Active and Partially Active Electrodes: Insights and Limitations

“…Consequently, the hydrogen‐saturated particles that impact the electrode begin producing H 2 directly via Equation (2) (the Heyrovsky step is the likely H 2 formation step on Pt nanoparticles) . This is in line with previous reports of a more step‐like response of Pt nanoparticle impacts in H 2 ‐saturated solution compared to N 2 ‐ or He‐saturated solutions . These results show that the use of an active electrode can provide valuable mechanistic insight into the reactions occurring at impacting particles by generating reactive species in situ.…”

“…We chose the hydrogen evolution reaction (HER) as a first model system to study particle impacts at an active electrode. Several groups have used the HER in collisional studies due to its inner‐sphere nature . As seen in the voltammograms in Figure A, the overpotential of the HER is approximately 200 mV larger on Au compared to Pt (the high scan rate was chosen to minimize deactivation of the Pt electrode, as discussed later).…”

“…The electrochemical nanoimpact technique has recently emerged as a means of measuring the properties of individual entities rather than ensembles . This method has recently been used to study particle size, porosity, and heterogenous catalytic rates on a single‐particle basis; these parameters are critically important to the performance of an electrocatalyst. While a wide variety of systems have been analyzed through particle‐electrode impacts, several typical schemes have emerged.…”

“…The requirement for an active particle‐inactive electrode in ECA schemes (or vice versa in blocking schemes) limits both the scope of particle‐electrode impact detection and the depth of mechanistic insight such impacts can reveal. ECA schemes have typically required the addition of an inner‐sphere redox probe, such as hydrogen peroxide or hydrazine, or used protons or oxygen already present in solution . Regardless of the redox species, the measurements require that the particle be more active toward the redox reaction than the electrode.…”

Characterising porosity in platinum nanoparticles

“…As an alternative, a recently developed single nanoparticle electrochemistry technique has enabled individual platinum nanoparticle surface areas to be measured. 22 Here a microelectrode is immersed into a solution containing a suspension of platinum nanoparticles and hydrogen gas. The hydrogen gas dissociatively chemisorbs on to the platinum surface and if the nanoparticle collides with an electrode potentiostated to a suitably oxidising potential then the chemisorbed layer of hydrogen atoms can be electrochemically oxidatively removed from the individual particle surface.…”