Electrodeposition of Platinum on Nanometer-Sized Carbon Electrodes

Abstract

Results for the electrodeposition of platinum on carbon electrodes of nanometer size are presented. It is shown that electrodes with very small electroactive areas simplify the study of the nucleation and growth mechanism involved in electrodeposition. Reducing the electroactive area of the substrate easily controls the number of nucleation sites. With the use of substrates having electroactive radii of a few nanometers, it is possible to form only one single growth center and to allow that center to grow independently. The current transient associated with the growth of such a single nucleus provides both kinetic and mechanistic information about the electrodeposition process. A mathematical formula for the current transient under combined electrokinetic and mass-transport control based on the work of Fletcher [J. Cryst. Growth 1983, 62, 505] and Kruijt et al. [J. Electroanal. Chem. 1994, 371, 13] is used to fit the transients to extract the exchange current density and diffusion coefficient of the reactants. For the Pt on carbon deposition process at low overpotentials, for which the electron-transfer steps control the overall deposition process, single nucleation is observed when the electrode is smaller than about 5 nm in size. It is found that the single nucleation and growth processes can also occur at relatively large electrodes (∼100 nm in size) when a high overpotential is applied so that a diffusion-controlled deposition process is established. Such a phenomenon is analyzed in terms of the depletion layer of electroactive species around the growing nucleus, and the effect that this has on the nucleation rate on the surrounding electrode surface.

Modifying the liquid/liquid interface: pores, particles and deposition

“…Thus, in principle, for r approaching 10 nm, interfacial rate constants exceeding 1 cm s À1 should be measurable. Again, formation of nanometre scale L/L interfaces has parallels with analogous work on the formation of ''nanoelectrodes'' using nanometre scale objects to define disc- 34,35 or band-shaped electrodes. 36 On the nanometre scale, a key issue becomes the fidelity of the interface: over this length scale, how reproducibly can we construct a conducting surface?…”

“…102 Studies of the deposition of metals on (solid) electrode surfaces have used microelectrodes in an attempt to reduce the number of nucleation sites toward one, and thereby simplify the analysis of the associated current response by eliminating the need to consider the overlap between multiple diffusion fields. 35,103 The study of silver deposition at the pipette-defined water/ DCE interface included some SEM of the deposits, which again suggested that the deposits were on the micron scale. Importantly this communication also provided a preliminary comparison of electrochemical and structural (SEM) data, suggesting that around seven silver nuclei were formed in a two micron radius pipette, 102 although it is not immediately clear if deposit aggregation can be distinguished from the formation of individual nuclei.…”

Temperature-Dependence of Deposition Rate and Current Efficiency in Platinum Electrodeposition at a Fixed Average Current Density

“…For instance, in platinum black that comprises platinum particle aggregates and has a porous structure, the effect of temperature [1] and additives [10][11][12][13][14] on the size of particle was investigated. No platinum particle aggregates at an initial growth stage developed into a dense thin film with a small surface roughness.…”

“…The reduction process of a platinum atom from a Pt(IV) ion analyzed by cyclic voltammetry was proposed as the following equation [13,16]:…”

Visualizing Zeptomole (Electro)Catalysis at Single Nanoparticles within an Ensemble

“…1,[5][6][7][8][9][10][11][12][13] However, as the vast majority of investigations have employed a large number of particles in a catalytic ensemble, the information obtained is limited due to unavoidable variations in NP size, shape and local environment. 14 Efforts to circumvent this limitation have been made by shifting to single particle measurements, [15][16][17][18][19][20] but such studies are rather challenging. 21 In general, single particle experiments fall into one of two categories.…”