80
3 Potential- or Adsorbate-Induced Changes in Surface Stress …
Fig. 3.8 Dependence of changes in surface stress on surface charge density q for the (111)textured Au (111) thin-film electrode in a 0.1 M HClO 4 (between 0.1 and 0.65 V (SCE) at 0.2 V s −1 ),
b 1 M H 2 SO 4 (between 0.75 and 0.95 V(SCE) at 0.2 V s −1 ), and c 0.1 M HClO 4 + 5 × 10 −3 M
CsCl (between 0.1 and 0.825 V(SCE) at 0.5 V s −1 ) [22]. Reprinted from [22], Copyright 1998,
with permission from Elsevier
the position of E pzc since the linear relationship between and q moves only in
parallel with the abscissa of Fig. 3.8 in response to the shift of E pzc .
In contrast to the linear dependence of on q, the dependence of changes in
surface tension γ on q is quadratic (or parabolic) as shown in Fig. 3.9 which is
transformed from the electrocapillary curves ( vs. E) of the Au (111) electrode
in 0.1 M HClO 4 solutions with and without 5 × 10
−3 M K 2 SO 4 [29]. In Fig. 3.9,
the value of is referred to zero at q = 0 C m
−2 corresponding to E pzc . If the
differential capacity of electric double layer c is potential-independent, the parabolic
dependence of γ on E or q can be derived from the Lippmann equation [30]:
= γ − γ pzc = − (E−Epzc)
2
2c
= −
q
2
2c
, where is referred to zero at E pzc (see
Eq. (1.126) in Sect. 1.9 of Chap. 1). The comparison between Figs. 3.8b and 3.9 for
the adsorption of SO 4
2− in the same range of q = 0 ~ 0.6 C m
−2 indicates that the
dependence of on q is larger by a factor of about 2.5 than the dependence of γ
on q.
3 Potential- or Adsorbate-Induced Changes in Surface Stress …
Fig. 3.8 Dependence of changes in surface stress on surface charge density q for the (111)textured Au (111) thin-film electrode in a 0.1 M HClO 4 (between 0.1 and 0.65 V (SCE) at 0.2 V s −1 ),
b 1 M H 2 SO 4 (between 0.75 and 0.95 V(SCE) at 0.2 V s −1 ), and c 0.1 M HClO 4 + 5 × 10 −3 M
CsCl (between 0.1 and 0.825 V(SCE) at 0.5 V s −1 ) [22]. Reprinted from [22], Copyright 1998,
with permission from Elsevier
the position of E pzc since the linear relationship between and q moves only in
parallel with the abscissa of Fig. 3.8 in response to the shift of E pzc .
In contrast to the linear dependence of on q, the dependence of changes in
surface tension γ on q is quadratic (or parabolic) as shown in Fig. 3.9 which is
transformed from the electrocapillary curves ( vs. E) of the Au (111) electrode
in 0.1 M HClO 4 solutions with and without 5 × 10
−3 M K 2 SO 4 [29]. In Fig. 3.9,
the value of is referred to zero at q = 0 C m
−2 corresponding to E pzc . If the
differential capacity of electric double layer c is potential-independent, the parabolic
dependence of γ on E or q can be derived from the Lippmann equation [30]:
= γ − γ pzc = − (E−Epzc)
2
2c
= −
q
2
2c
, where is referred to zero at E pzc (see
Eq. (1.126) in Sect. 1.9 of Chap. 1). The comparison between Figs. 3.8b and 3.9 for
the adsorption of SO 4
2− in the same range of q = 0 ~ 0.6 C m
−2 indicates that the
dependence of on q is larger by a factor of about 2.5 than the dependence of γ
on q.