3 The Measurements of the Oxygen Reduction Reaction
53
samples, may need to increase the ratio of alcohol (ethanol or isopropanol) to water for
better dispersion. Increasing the ratio of isopropanol to water and multiple ultrasonic
oscillations can obtain a slurry with a good dispersion state, thereby improving
the dispersibility and electrocatalytic activity of the catalytic layer. The hydrophilic
catalyst is well dispersed in a mixed liquid of Nafion solution and water.
The catalyst-coated electrode is first wetted with an electrolyte solution to have
no bubbles on its surface. After the electrode is mounted, adjust the distance between
the electrode surface and the Lujin capillary (about 2 times the diameter of the Lujin
capillary), and try to rotate the electrode two to three times to remove the air bubbles
on the electrode surface. The potentiostat was turned on, stabilized at 1600 rpm, and
activated at 50–200 mV.s
−1 , and activated until a stable curve was obtained.
3.3.3 Effect of Electrolyte Concentration
on the Measurement of Oxygen Reduction
Performance of Pt/C Catalyst
At present, most research teams use the rotating ring-disk electrode (RRDE) to
study the hydrogenation and oxygen reduction performance of the catalyst. The
advantage of this test method is that it can deduct the effect of mass transfer on
the measured current, thus reflecting intrinsic properties of the catalyst. In order to
ultimately compare the results of RRDE with actual fuel cell membrane electrode
(MEA) testing, factors affecting RRDE test results and activity characterization need
to be noted. These factors include the determination of the active area, the effects
of ion adsorption, the mass transfer effects of the Nafion membrane, and the effects
of electrolytes. The first three factors have been studied accordingly. However, in
the treatment of electrolytes, it is most commonly used to measure the resistance of
the solution by AC impedance method, or to think that the solution is completely
conductive, and the solution resistance is negligible. From an electrochemical point
of view, the ionic strength of the electrolyte solution will greatly affect the results of
the oxygen reduction test. The easiest way to reduce the resistance of the solution and
increase the conductance of the solution is to add a certain concentration of strong
electrolyte to the solution to increase the number of conductive ions per unit volume
of solution. In the study of this book, try to introduce different concentrations of
strong electrolyte salt sodium perchlorate in 0.1 M HClO 4 to reduce the solution
resistance, and study its effect on the oxygen reduction performance of commercial
Pt/C catalyst under the oxygen reduction standard test.
3.3.3.1 Electrochemical Characterization
Figure 3.6 is a cyclic voltammetric scan of a commercial Pt/C catalyst in different
electrolyte solutions. It can be seen that the addition of different concentrations of
53
samples, may need to increase the ratio of alcohol (ethanol or isopropanol) to water for
better dispersion. Increasing the ratio of isopropanol to water and multiple ultrasonic
oscillations can obtain a slurry with a good dispersion state, thereby improving
the dispersibility and electrocatalytic activity of the catalytic layer. The hydrophilic
catalyst is well dispersed in a mixed liquid of Nafion solution and water.
The catalyst-coated electrode is first wetted with an electrolyte solution to have
no bubbles on its surface. After the electrode is mounted, adjust the distance between
the electrode surface and the Lujin capillary (about 2 times the diameter of the Lujin
capillary), and try to rotate the electrode two to three times to remove the air bubbles
on the electrode surface. The potentiostat was turned on, stabilized at 1600 rpm, and
activated at 50–200 mV.s
−1 , and activated until a stable curve was obtained.
3.3.3 Effect of Electrolyte Concentration
on the Measurement of Oxygen Reduction
Performance of Pt/C Catalyst
At present, most research teams use the rotating ring-disk electrode (RRDE) to
study the hydrogenation and oxygen reduction performance of the catalyst. The
advantage of this test method is that it can deduct the effect of mass transfer on
the measured current, thus reflecting intrinsic properties of the catalyst. In order to
ultimately compare the results of RRDE with actual fuel cell membrane electrode
(MEA) testing, factors affecting RRDE test results and activity characterization need
to be noted. These factors include the determination of the active area, the effects
of ion adsorption, the mass transfer effects of the Nafion membrane, and the effects
of electrolytes. The first three factors have been studied accordingly. However, in
the treatment of electrolytes, it is most commonly used to measure the resistance of
the solution by AC impedance method, or to think that the solution is completely
conductive, and the solution resistance is negligible. From an electrochemical point
of view, the ionic strength of the electrolyte solution will greatly affect the results of
the oxygen reduction test. The easiest way to reduce the resistance of the solution and
increase the conductance of the solution is to add a certain concentration of strong
electrolyte to the solution to increase the number of conductive ions per unit volume
of solution. In the study of this book, try to introduce different concentrations of
strong electrolyte salt sodium perchlorate in 0.1 M HClO 4 to reduce the solution
resistance, and study its effect on the oxygen reduction performance of commercial
Pt/C catalyst under the oxygen reduction standard test.
3.3.3.1 Electrochemical Characterization
Figure 3.6 is a cyclic voltammetric scan of a commercial Pt/C catalyst in different
electrolyte solutions. It can be seen that the addition of different concentrations of