3 The Measurements of the Oxygen Reduction Reaction
75
the limiting current. From this perspective, the current optimization methods can be
simply classified into three categories. The first is to increase the peak potential of
oxygen reduction and inhibit the oxidation of Pt. The main methods are Pt-based
alloys and ionic liquids. Second, the slope of the curve of the concentration polarization and the electrochemical polarization mixing control region is increased, that
is, the internal resistance of the catalyst is lowered or the conductivity of the catalyst
is improved. Qu et al. [20] reported that the internal resistance of nitrogen-doped
graphene is very small, although the oxygen reduction catalytic activity of this material is still smaller than Pt, especially in the low overpotential region, but it is also
a potential material for optimizing oxygen reduction activity. The third method is
to reduce the loading of Pt or increase the utilization rate of Pt. The main methods
include dealloying, increasing the proportion of Pt(111) crystal plane, increasing the
active area, and preparing various special nanostructured catalysts.
Although there are many reports on high-activity oxygen reduction catalysts, Ptbased catalysts are still put into practical use, mainly Pt/C catalysts. The research
focuses on the following aspects.
(i) Rotating ring disk electrode test. The effectiveness of the catalyst oxygen reduction still needs further exploration, especially the oxygen reduction simulation
test of nonprecious metal catalysts. In many of the literatures already reported,
the rotating ring disk electrode test results of most of the new catalysts are highly
reproducible and almost identical to actual cell stack test results. However, with
the further exploration of catalysts, especially the discovery of nonprecious
metal catalysts, it is still unknown whether the rotary ring electrode oxygen
reduction simulation test is still valid.
(ii) The relationship between the active substances, the relationship between the
carrier and the doping elements, and the activeness of the substances still require
more experimental exploration, such as environmental spherical aberration
correction electron microscopy and DFT simulation calculations.
(iii) Exploring new forms of catalysts, such as simulated enzyme catalysts, which
have lower oxygen reduction over potentials than Pt(111) planes, and even
lower than the currently reported Pt 3 Ni alloys with the highest activity. It also
includes the preparation of self-assembled nanostructured catalysts and the
like.
(iv) The high activity catalysts simulated by the simulation should be tested on
actual stacks to investigate their activity and stability.
(v) Reduce the cost of an efficient synthetic process for commercialization
purposes.
3.6 Electrochemical Determination of Specific Surface Area
The specific activity of the catalyst is required, first of all, to know its electrochemical
specific surface area. Ref. [21] details the principle and method of specific surface
area measurement. Here we only mention the most commonly used electrochemical
test methods.
75
the limiting current. From this perspective, the current optimization methods can be
simply classified into three categories. The first is to increase the peak potential of
oxygen reduction and inhibit the oxidation of Pt. The main methods are Pt-based
alloys and ionic liquids. Second, the slope of the curve of the concentration polarization and the electrochemical polarization mixing control region is increased, that
is, the internal resistance of the catalyst is lowered or the conductivity of the catalyst
is improved. Qu et al. [20] reported that the internal resistance of nitrogen-doped
graphene is very small, although the oxygen reduction catalytic activity of this material is still smaller than Pt, especially in the low overpotential region, but it is also
a potential material for optimizing oxygen reduction activity. The third method is
to reduce the loading of Pt or increase the utilization rate of Pt. The main methods
include dealloying, increasing the proportion of Pt(111) crystal plane, increasing the
active area, and preparing various special nanostructured catalysts.
Although there are many reports on high-activity oxygen reduction catalysts, Ptbased catalysts are still put into practical use, mainly Pt/C catalysts. The research
focuses on the following aspects.
(i) Rotating ring disk electrode test. The effectiveness of the catalyst oxygen reduction still needs further exploration, especially the oxygen reduction simulation
test of nonprecious metal catalysts. In many of the literatures already reported,
the rotating ring disk electrode test results of most of the new catalysts are highly
reproducible and almost identical to actual cell stack test results. However, with
the further exploration of catalysts, especially the discovery of nonprecious
metal catalysts, it is still unknown whether the rotary ring electrode oxygen
reduction simulation test is still valid.
(ii) The relationship between the active substances, the relationship between the
carrier and the doping elements, and the activeness of the substances still require
more experimental exploration, such as environmental spherical aberration
correction electron microscopy and DFT simulation calculations.
(iii) Exploring new forms of catalysts, such as simulated enzyme catalysts, which
have lower oxygen reduction over potentials than Pt(111) planes, and even
lower than the currently reported Pt 3 Ni alloys with the highest activity. It also
includes the preparation of self-assembled nanostructured catalysts and the
like.
(iv) The high activity catalysts simulated by the simulation should be tested on
actual stacks to investigate their activity and stability.
(v) Reduce the cost of an efficient synthetic process for commercialization
purposes.
3.6 Electrochemical Determination of Specific Surface Area
The specific activity of the catalyst is required, first of all, to know its electrochemical
specific surface area. Ref. [21] details the principle and method of specific surface
area measurement. Here we only mention the most commonly used electrochemical
test methods.