Substrate Structural Effects on the Synthesis and Electrochemical Properties of Platinum Nanoparticles on Highly Oriented Pyrolytic Graphite

Abstract

Platinum nanoparticles have been prepared by potentiostatic multipulse electrodeposition with controlled nucleation and growth on freshly cleaved and electrochemically oxidized highly oriented pyrolytic graphite.The influence of the applied potential sequence on the size distribution was investigated. For short electrolysis times, the deposition of nanoparticles takes place via a progressive nucleation mechanism. A narrow size distribution was obtained by controlling independently the nucleation and growth steps, and particles with heights between 52 and 1.4 nm could be prepared by altering the pulse parameters. Anodic oxidation of the substrate had a large influence on the particle size, resulting in the preparation of particles 1.4 nm in height. XPS demonstrated that Pt particles of small size were readily oxidized. The rate of electrochemical methanol oxidation showed a dependence on the particle size, and no oxidation of methanol could be observed for the smaller sizes investigated.

Nucleation and Aggregative Growth of Palladium Nanoparticles on Carbon Electrodes: Experiment and Kinetic Model

“…This grade of HOPG gives rise to a relatively high step density on the basal surface compared to some other HOPG grades. 29 HOPG was further considered as the main substrate in this work because it has been used extensively for electrochemical nucleation and growth studies [30][31][32] and is easily refreshed through cleavage. 29 For nanoscale imaging, a carbon film-coated 400 mesh gold (S160A4, Agar Scientific) TEM grid was used.…”

Electrochemistry of Nanoparticles

“…Examples of this approach are: the electrodeposition of NPs from a solution containing the metal ion, either onto the bare support electrode [74][75][76][77][78][79][80][81][82] or onto the support electrode modified with a polymer film; [78,[83][84][85][86] electroless deposition; [77,87,88] and vacuum evaporation. Examples of this approach are: the electrodeposition of NPs from a solution containing the metal ion, either onto the bare support electrode [74][75][76][77][78][79][80][81][82] or onto the support electrode modified with a polymer film; [78,[83][84][85][86] electroless deposition; [77,87,88] and vacuum evaporation.…”

“…Second, during growth, depletion layers of neighboring NPs can start to overlap, causing these NPs to grow more slowly compared to those which are diffusionally isolated. [71,74,75,77,[104][105][106][107][108][109] Slow NP growth at low overpotential also diminishes the concentration polarization near the substrate, so that local NP coverage has less effect on the extent of growth of individual NPs. As the number of nearby NPs will vary from one NP to the next in a random ensemble, this leads to a broadening of the size distribution during NP growth.…”

“…[101] Consequently, the size of a single NP correlates with the local number density of NPs. [71,74,75,77,[104][105][106][107][108][109] Depletion effects can also be minimized by incorporating a local source of convection within the depletion layer. [101] Third, (surface-mediated) Ostwald ripening can occur, whereby large NPs grow at the expense of the small NPs because of the size-dependence of the free energy of stabilization of an NP.…”

“…In this approach, the formation and immobilization of NPs on a support electrode takes place in a single step. Examples of this approach are: the electrodeposition of NPs from a solution containing the metal ion, either onto the bare support electrode [74][75][76][77][78][79][80][81][82] or onto the support electrode modified with a polymer film; [78,[83][84][85][86] electroless deposition; [77,87,88] and vacuum evaporation. [89][90][91][92][93] Electrodeposition is by far the most popular of these methods, as it makes use of electrochemical equipment, ensures an electrical contact between the NP and substrate, and provides many tunable parameters, such as the deposition potential or current, time, temperature, and electrolyte composition, [74,75,94] to adjust the size, shape, and spatial distribution of the electrodeposited NPs.…”