80
C. Juhong et al.
The absorption and desorption of hydroxide and oxygen began to appear in the
fourth region. As the potential increases, the adsorbed oxygen atoms and hydroxide
ions formed on the surface of the electrode combine with platinum to form oxides
(PtO x ) and hydroxides, and even oxygen evolution occurs.
In an acidic solution, Conway et al. believe that at 1.18 V (vs. RHE), the platinum
surface is filled with a single layer of PtOH.
Pt + H 2 O → Pt − OH + H + + e
−
(3.79)
Subsequently, PtOH is further reacted to form PtO. Gregory and Jerkewic et al.
proposed a potential for forming a single layer of PtO of 1.4 V (vs. RHE).
In an alkaline solution, hydroxide adsorption occurs at about 0.55 V, and the
reaction equation is as follows:
Pt + OH
−
→ Pt−OH + e
−
(3.80)
PtO is formed at about 0.8 V.
Pt−OH + OH
−
→ Pt−O + H 2 O + e
−
(3.81)
Therefore, this area is called the “oxygen zone.” If the reverse phase of the oxygen
adsorption zone is reached, as the potential becomes negative, oxygen desorption
(reduction), electric double layer charging, and hydrogen adsorption process will
occur in sequence.
The hydrogen adsorption zone of the second region is integrated, and the result
is the amount of electricity in the zone. Since the region contains the charging of the
electric double layer, the result obtained by subtracting this part of the charging power
is the hydrogen adsorption amount, and the calculation formula of the adsorption
amount of the hydrogen adsorption region is as shown in (3.82).
Q H −adsor ption =
E h
E L
(I − I DL )d E
v
(3.82)
In the above formula,v is the scanning speed, I is the adsorption region current,
I DL is the electric double layer charging current, the lower integration limit E L is the
potential at the end of the hydrogen underpotential deposition, generally between
0.03 and 0.05 V, and the upper limit of integration E h is hydrogen. The end of the
adsorption zone determines or the initial potential of the adsorbed hydrogen, typically
between 0.45 and 0.5 V.
Taking the shaded portion of Fig. 3.22 as an example, the result is the hydrogen
adsorption energy Q H-adsorption , and the hydrogen adsorption energy Q H-adsorption is
substituted into (3.82) to obtain the electrochemical specific surface area. The detailed
calculation process is as follows.
C. Juhong et al.
The absorption and desorption of hydroxide and oxygen began to appear in the
fourth region. As the potential increases, the adsorbed oxygen atoms and hydroxide
ions formed on the surface of the electrode combine with platinum to form oxides
(PtO x ) and hydroxides, and even oxygen evolution occurs.
In an acidic solution, Conway et al. believe that at 1.18 V (vs. RHE), the platinum
surface is filled with a single layer of PtOH.
Pt + H 2 O → Pt − OH + H + + e
−
(3.79)
Subsequently, PtOH is further reacted to form PtO. Gregory and Jerkewic et al.
proposed a potential for forming a single layer of PtO of 1.4 V (vs. RHE).
In an alkaline solution, hydroxide adsorption occurs at about 0.55 V, and the
reaction equation is as follows:
Pt + OH
−
→ Pt−OH + e
−
(3.80)
PtO is formed at about 0.8 V.
Pt−OH + OH
−
→ Pt−O + H 2 O + e
−
(3.81)
Therefore, this area is called the “oxygen zone.” If the reverse phase of the oxygen
adsorption zone is reached, as the potential becomes negative, oxygen desorption
(reduction), electric double layer charging, and hydrogen adsorption process will
occur in sequence.
The hydrogen adsorption zone of the second region is integrated, and the result
is the amount of electricity in the zone. Since the region contains the charging of the
electric double layer, the result obtained by subtracting this part of the charging power
is the hydrogen adsorption amount, and the calculation formula of the adsorption
amount of the hydrogen adsorption region is as shown in (3.82).
Q H −adsor ption =
E h
E L
(I − I DL )d E
v
(3.82)
In the above formula,v is the scanning speed, I is the adsorption region current,
I DL is the electric double layer charging current, the lower integration limit E L is the
potential at the end of the hydrogen underpotential deposition, generally between
0.03 and 0.05 V, and the upper limit of integration E h is hydrogen. The end of the
adsorption zone determines or the initial potential of the adsorbed hydrogen, typically
between 0.45 and 0.5 V.
Taking the shaded portion of Fig. 3.22 as an example, the result is the hydrogen
adsorption energy Q H-adsorption , and the hydrogen adsorption energy Q H-adsorption is
substituted into (3.82) to obtain the electrochemical specific surface area. The detailed
calculation process is as follows.