34
C. Juhong et al.
makes this test technique difficult to perform accurate analysis. X-ray absorption spectroscopy techniques such as extended X-ray absorption fine structure
spectroscopy (EXAFS) and near-edge X-ray absorbing fine structure spectroscopy
(NEXAFS) can also be used for oxygen reduction mechanism studies, but the information about the reaction mechanism that can be obtained is very limited [1–4].
Strasser et al. used Synchrotron radiation X-ray diffraction to study the structural
properties of PtCo particles [5, 6]. Wieckowski et al. improved the NMR method
to make it suitable for electrochemical working conditions, and used this method to
study the oxygen reduction reaction [7].
The earliest mechanism for studying the mechanism of oxygen reduction in situ
is the fixed electrode method proposed by Damjanovic et al., but the fixed electrode
method was greatly affected by the mass transfer of the solution. The current in situ
study of oxygen reduction kinetics mainly uses the rotating disk electrode method
(see 3.2.2 for detailed analysis). Rotating disk electrode is a fluid dynamic electrode
that increases liquid flow by convection and improves mass transfer. This electrode
can be used to study the progress of electrochemical reactions in steady state, transient, constant voltage or constant current conditions. The voltage and current data
obtained by rotating the disk electrode are plotted as a Koutecký-Levich curve with
the reciprocal of the current and the reciprocal of the square of the electrode speed,
the intercept of the curve is the limiting current density. The limiting current density
is proportional to the electrochemical reaction rate and can therefore be used to
compare the kinetic mechanisms of different reactions. Since the rotating disk electrode cannot obtain the information of the oxygen reduction reaction intermediate
product, a rotating ring disk electrode has been researched on the basis of the rotating
disk electrode for studying the intermediate products in the reaction process, such as
H 2 O 2 in the oxygen reduction reaction. And this method is used to study the factors
affecting oxygen reduction, such as the influence of different electrolyte solutions,
including H 3 PO 4 , H 2 SO 4 , HClO 4 , trifluoromethanesulfonic acid (TFMSA) and the
like. In addition, the commonly used catalyst active material platinum and the proton
membrane Nafion for PEMFC were slurried to form a catalyst electrode for oxidative
kinetics studies.
3.2 Research Method of Electrochemical Oxygen
Reduction Reaction
3.2.1 Cyclic Voltammetry
There are many experimental methods for testing the polarization curves of electrochemical systems. According to the types of independent variables, they can be
simply divided into constant current method (control current method) and constant
potential method (control potential method). The constant current method records
the change relationship (polarization curve) between the corresponding electrode
C. Juhong et al.
makes this test technique difficult to perform accurate analysis. X-ray absorption spectroscopy techniques such as extended X-ray absorption fine structure
spectroscopy (EXAFS) and near-edge X-ray absorbing fine structure spectroscopy
(NEXAFS) can also be used for oxygen reduction mechanism studies, but the information about the reaction mechanism that can be obtained is very limited [1–4].
Strasser et al. used Synchrotron radiation X-ray diffraction to study the structural
properties of PtCo particles [5, 6]. Wieckowski et al. improved the NMR method
to make it suitable for electrochemical working conditions, and used this method to
study the oxygen reduction reaction [7].
The earliest mechanism for studying the mechanism of oxygen reduction in situ
is the fixed electrode method proposed by Damjanovic et al., but the fixed electrode
method was greatly affected by the mass transfer of the solution. The current in situ
study of oxygen reduction kinetics mainly uses the rotating disk electrode method
(see 3.2.2 for detailed analysis). Rotating disk electrode is a fluid dynamic electrode
that increases liquid flow by convection and improves mass transfer. This electrode
can be used to study the progress of electrochemical reactions in steady state, transient, constant voltage or constant current conditions. The voltage and current data
obtained by rotating the disk electrode are plotted as a Koutecký-Levich curve with
the reciprocal of the current and the reciprocal of the square of the electrode speed,
the intercept of the curve is the limiting current density. The limiting current density
is proportional to the electrochemical reaction rate and can therefore be used to
compare the kinetic mechanisms of different reactions. Since the rotating disk electrode cannot obtain the information of the oxygen reduction reaction intermediate
product, a rotating ring disk electrode has been researched on the basis of the rotating
disk electrode for studying the intermediate products in the reaction process, such as
H 2 O 2 in the oxygen reduction reaction. And this method is used to study the factors
affecting oxygen reduction, such as the influence of different electrolyte solutions,
including H 3 PO 4 , H 2 SO 4 , HClO 4 , trifluoromethanesulfonic acid (TFMSA) and the
like. In addition, the commonly used catalyst active material platinum and the proton
membrane Nafion for PEMFC were slurried to form a catalyst electrode for oxidative
kinetics studies.
3.2 Research Method of Electrochemical Oxygen
Reduction Reaction
3.2.1 Cyclic Voltammetry
There are many experimental methods for testing the polarization curves of electrochemical systems. According to the types of independent variables, they can be
simply divided into constant current method (control current method) and constant
potential method (control potential method). The constant current method records
the change relationship (polarization curve) between the corresponding electrode