A mechanistic study of Pt particle electrodeposition and growth on a self-assembled monolayer as an active template

Platinum is an essential component in many commercial catalytic processes. However, due to its cost and availability considerable effort is made to control the amount, location, and accessibility of the platinum species on an electrode surface. The current study investigates a low-cost, and versatile method for the deposition of N particles using a self-assembled monolayer (SAM) as an active assisted template on a gold electrode. Alkane (HSCH2(CH2)(8)CH3), alcohol (HSCH2(CH2)(9)CH2OH) and carboxylate (HSCH2(CH2)(8)CH2COOH) terminated monolayers were used to probe the impact of hydrophobicity on particle size, population density and growth mechanism. Cyclic voltammetry (CV) and chronoamperometry (CA) were employed to induce particle growth. From the CA data a dimensionless theoretical plot was calculated based on the Scharifker and Hills model to establish the mechanism as either progressive or instantaneous. The time-dependent study revealed a progressive nucleation mechanism for N particles synthesized on all three electrode surfaces, whereas microscopy and image analysis revealed an instantaneous nucleation mechanism for the alkane template only and progressive nucleation pathways for the alcohol and carboxylate SAM surfaces. The results indicated that SAM templating could be used to effectively control particle growth in a predictable fashion, however there is a limitation in application of the existing model due to a combination of factors including the migration of the SAM monomers on the electrode surface, the hydrophobicity of the terminal moieties and the occurrence of secondary and subsequent nucleation and growth phases. In addition, post-particle deposition CV was used to determine the impact of the SAM template on the active area of the N particles available for catalysis and showed that the hydrophobic SAM coatings gave significantly higher activity.

Automated summary

This study investigates a low-cost method using a self-assembled monolayer as a template for the deposition of N particles. The impact of hydrophobicity on particle size, population density, and growth mechanism is explored. The results show that SAM templating can effectively control particle growth, but there are limitations in the existing model.