posted on 2023-01-09, 21:13authored byNicholas
J. Vitti, Pavel Majumdar, Henry S. White
The
induction times for electrodeposition of individual Ag nanoparticles
on Pt nanodisk electrodes in acetonitrile were used to determine the
critical nucleus size and activation energy barrier associated with
the formation of Ag nuclei. Induction times for the nucleation and
growth of a single Ag nanoparticle were determined following the application
of a potential step to reduce Ag+ at overpotentials, η,
ranging from −130 to −70 mV. Sufficiently small Pt electrodes
(5.1 × 10–10–2.6 × 10–11 cm2) were used to ensure that the detection of a single
Ag nucleation event occurred during the experimental observation time
(150 ms–1000 s). Multiple measurements of Ag nucleation induction
times were recorded to determine nucleation rates as a function of
η using cumulative probability theory. Both classical nucleation
theory (CNT) and the atomistic theory of electrochemical nucleation
were employed to analyze experimental nucleation rates, without a
requisite knowledge of the nucleus geometry or surface free energy.
Using the CNT, the number of atoms comprising the critical size nucleus, Nc, was estimated to be 1–9 atoms for
η ranging from −130 to −70 mV, in good agreement
with 1–5 atoms obtained using atomistic theory. The experimental
nucleation rates were also used to determine the activation energy
barriers for nucleation from the CNT, which varied from 3.31 ±
0.05 to 13 ± 1 kT over the same range of η.