60
C. Juhong et al.
covered, which will affect the electrochemical active area of the catalyst and the
magnitude of the oxygen reduction limit current. In addition, since the calculation of
the electrochemical active area and the oxygen reduction mass activity is calculated
based on the geometrical area of the electrode, it is assumed here that the catalyst
film uniformly covers the surface of the electrode, and the actual situation is that the
catalyst film obtained by the static drying method is It is not uniform coverage, so
the calculation results of the electrochemical active area and the oxygen reduction
mass activity are more deviated than the actual values.
3.3.4.2 Rotary Drying Method
In view of the problem of uneven film formation quality in the static drying method,
Garsany et al. developed a spin-drying method [18, 19]. The specific method of
operation is to invert the rotating disk device, and the electrode on which the catalyst
slurry is dropped is turned upward to be rotated to obtain a dried catalyst film. The
speed of rotation will cause the catalyst slurry to splash out of the rotating disk
electrode. If the rotation speed is too slow, it will not be uniformly dried, and the
rotation speed is generally controlled at 700 rpm.
It can be seen from Fig. 3.12 that the film formed by the spin-drying method
has a good film-forming quality, and the film-forming quality is relatively uniform
regardless of the center of the rotating disk electrode or the edge portion. This is
because under the conditions of spin drying, the catalyst slurry can be evenly spread
on the surface of the rotating disk electrode, which is more favorable for the solvent
in the catalyst slurry to be uniformly volatilized.
It can be seen from Fig. 3.13 that the electrochemical activity areas of the catalysts
obtained by the static drying method and the rotary drying method are relatively
uniform, but the oxygen reduction activities are quite different. This is because the
catalyst film obtained by the spin-drying method is relatively uniform, and thus the
electrode is less affected by the surface effect, which is more advantageous for the
electrolyte and oxygen to diffuse on the surface of the catalyst. Moreover, the spindrying method is more reproducible (see Fig. 3.14) and is therefore more suitable
for studying the electrocatalytic activity of the catalyst.
3.4 Oxygen Reduction Reaction Test Considerations
The factors that need to be noted during the test are as follows.
The effect of different anions. Markovic et al. found that the reduction of oxygen
is greatly inhibited in sulfur- and chlorine-containing acidic electrolyte solutions,
which is more pronounced in chlorine-containing electrolyte solutions. Schmidt et al.
found that the presence of Cl
− in the electrolyte solution does not change the decisive step of the cathode reduction reaction of commercial Pt/C catalysts, but the
C. Juhong et al.
covered, which will affect the electrochemical active area of the catalyst and the
magnitude of the oxygen reduction limit current. In addition, since the calculation of
the electrochemical active area and the oxygen reduction mass activity is calculated
based on the geometrical area of the electrode, it is assumed here that the catalyst
film uniformly covers the surface of the electrode, and the actual situation is that the
catalyst film obtained by the static drying method is It is not uniform coverage, so
the calculation results of the electrochemical active area and the oxygen reduction
mass activity are more deviated than the actual values.
3.3.4.2 Rotary Drying Method
In view of the problem of uneven film formation quality in the static drying method,
Garsany et al. developed a spin-drying method [18, 19]. The specific method of
operation is to invert the rotating disk device, and the electrode on which the catalyst
slurry is dropped is turned upward to be rotated to obtain a dried catalyst film. The
speed of rotation will cause the catalyst slurry to splash out of the rotating disk
electrode. If the rotation speed is too slow, it will not be uniformly dried, and the
rotation speed is generally controlled at 700 rpm.
It can be seen from Fig. 3.12 that the film formed by the spin-drying method
has a good film-forming quality, and the film-forming quality is relatively uniform
regardless of the center of the rotating disk electrode or the edge portion. This is
because under the conditions of spin drying, the catalyst slurry can be evenly spread
on the surface of the rotating disk electrode, which is more favorable for the solvent
in the catalyst slurry to be uniformly volatilized.
It can be seen from Fig. 3.13 that the electrochemical activity areas of the catalysts
obtained by the static drying method and the rotary drying method are relatively
uniform, but the oxygen reduction activities are quite different. This is because the
catalyst film obtained by the spin-drying method is relatively uniform, and thus the
electrode is less affected by the surface effect, which is more advantageous for the
electrolyte and oxygen to diffuse on the surface of the catalyst. Moreover, the spindrying method is more reproducible (see Fig. 3.14) and is therefore more suitable
for studying the electrocatalytic activity of the catalyst.
3.4 Oxygen Reduction Reaction Test Considerations
The factors that need to be noted during the test are as follows.
The effect of different anions. Markovic et al. found that the reduction of oxygen
is greatly inhibited in sulfur- and chlorine-containing acidic electrolyte solutions,
which is more pronounced in chlorine-containing electrolyte solutions. Schmidt et al.
found that the presence of Cl
− in the electrolyte solution does not change the decisive step of the cathode reduction reaction of commercial Pt/C catalysts, but the