Structural
Dynamics of the Electrical Double Layer during Capacitive Charging/Discharging
Processes
- Publication date
- Publisher
Abstract
Transitional
structures of Cs<sup>+</sup> at the outer Helmholtz plane (OHP) have
been determined using time-resolved X-ray diffraction during the double-layer
charging/discharging on the Ag(100) electrode in CsBr solution. At
the double-layer potential region at which c(2 × 2)-Br is formed
on Ag(100), the transient current comprises two exponential terms
with different time scales: a rapid and a slow one are due to the
dielectric polarization of water molecules and the transfer of Cs<sup>+</sup>, respectively. The slow term is composed of different dynamic
processes of Cs<sup>+</sup> during charging and discharging. When
the potential is stepped in the positive direction, the coverage of
Cs<sup>+</sup> at the OHP decreases. In this step, the transient X-ray
intensity at the (0 0 1) reflection, which is sensitive to the OHP
structure, shows that Cs<sup>+</sup> is released from the OHP according
to exponential function of time. The decay of transient intensity
of X-ray has a time scale similar to that of the current transient
measurement. On the other hand, the accumulation process of Cs<sup>+</sup> from the diffuse double layer to the OHP comprises two different
kinetic processes after a potential step in the negative direction:
a rapid one is the accumulation of Cs<sup>+</sup> near the outer layer,
and a slow one is the structural stabilization of the Cs<sup>+</sup> layer