The Role of Nanocluster Aggregation, Coalescence, and Recrystallization in the Electrochemical Deposition of Platinum Nanostructures

Abstract

By using an optimized characterization approach that combines aberration-corrected transmission electron microscopy, electron tomography, and in situ ultrasmall angle X-ray scattering (USAXS), we show that the early stages of Pt electrochemical growth on carbon substrates may be affected by the aggregation, selfalignment, and partial coalescence of nanoclusters of d ≈ 2 nm. The morphology of the resulting nanostructures depends on the degree of coalescence and recrystallization of nanocluster aggregates, which in turn depends on the electrodeposition potential. At low overpotentials, a self-limiting growth mechanism may block the epitaxial growth of primary nanoclusters and results in loose dendritic aggregates. At more negative potentials, the extent of nanocluster coalescence and recrystallization is larger and further growth by atomic incorporation may be allowed. On one hand, this suggests a revision of the Volmer−Weber island growth mechanism. Whereas this theory has traditionally assumed direct attachment as the only growth mechanism, it is suggested that nanocluster self-limiting growth, aggregation, and coalescence should also be taken into account during the early stages of nanoscale electrodeposition. On the other hand, depending on the deposition potential, ultrahigh porosities can be achieved, turning electrodeposition in an ideal process for highly active electrocatalyst production without the need of using high surface area carbon supports.

Potentiostatic electrodeposition of Pt on GC and on HOPG at low loadings: Analysis of the deposition transients and the structure of Pt deposits

“…1a) the nucleation maximum is preceded by a pronounced current decay at low deposition times. Similar decaying current transients at deposition times exceeding those characteristic of the double layer charging, have also been reported in the literature [20,33,34]. Analysis of the deposition transients for Pt (IV) in logarithmic coordinates (Fig.…”

Monitoring Simultaneous Electrochemical Reactions with Single Particle Imaging

“…This type of growth has been previously used to describe the electrodeposition of various metal NPs; [32,33] however, our report is the first to describe this mechanism for Ag x O y growth using silver nanoparticles as feedstock. 1.2 V vs Pt), Ag NPs electrodissolve to produce Ag + , which subsequently electrodeposits as Ag x O y particles at a spatially distinct site on the same electrode surface.…”

“…The growth mechanism for the Ag x O y particles appears as aggregative growth, in which smaller nanoclusters form, then diffuse on the surface, and ultimately agglomerate into a larger nanoparticle. This type of growth has been previously used to describe the electrodeposition of various metal NPs; [32,33] however, our report is the first to describe this mechanism for Ag x O y growth using silver nanoparticles as feedstock. In addition to the oxidation reactions involving the dissolution of Ag(s) and deposition of Ag x O y , we also find that catalytic oxidation of water occurs, affecting the local pH and impacting the dissolution and growth kinetics of the varying particles under different potential conditions.…”

“…Instead, we propose that the electrodeposition of Ag x O y particles occurs dominantly based on an aggregative growth mechanism, [32,33] where the generated Ag + electrodeposits as Ag x O y clusters near the oxidizing Ag NPs (since the concentration of Ag + near them is sufficiently high to overcome the critical threshold). These clusters are not possible to detect using dark-field techniques because of their smaller size; however, over time, the clusters undergo surface diffusion and aggregate to grow as a particle that can be detected optically.…”

Template assisted preparation of high surface area macroporous supports with uniform and tunable nanocrystal loadings

“…[22][23][24] For improving the uniformity of nanocrystal coatings in macropores, electrochemical deposition can be used to prepare nanocrystals that exhibit limited agglomeration and increased mass efficiency. [25][26][27] This technique is limited to precious metal based support materials because the solutions used for the electroless and electrodeposition of precious metal catalysts are typically corrosive to lesser noble metals through processes of galvanic replacement. 20,23 Solutions of Pd and Pt salts for these processes are often prepared at a low pH to improve their stability.…”