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Y. Li et al.
of the volcano map, and its surface has the highest ORR activity. Among them, the
activity of chalcogenide of Rh is the same as that of Ru. The ORR activity of Rh
selenide is higher than its sulfide, which is consistent with experimental results [231].
Feng et al. [229] used XC-72 carbon powder as a carrier to prepare Co 3 S 4 and
CoSe 2 nanoparticles without using a surfactant. The obtained composite catalyst
particles are small and uniformly supported. In 0.5 M H 2 SO 4 solution, the on-set
potential of both catalysts can reach 0.7 V (vs. RHE). Nekooi et al. [232] used
microwave-assisted/polyol method to prepare CoSe nanoparticles with a particle
size of 8 nm on nanopore carbon. Its on-set potential reached 0.823 V (vs. SHE).
The calculated results according to the Koutecky–Levich equation indicate that the
reaction ORR process is a four-electron process. In addition, such materials are
resistant to methanol and formic acid.
4.5 Metal-Free Catalysts
The discovery and research of metal-free catalysts have opened up new approaches
and directions to replace precious metal oxygen reduction catalysts. The current
research results show that compared with metal-based catalysts, non-metallic oxygen
reduction catalysts have unparalleled advantages in terms of stability and anti-toxicity
performance, which is a solution to the current stability and anti-toxicity of metalbased oxygen reduction catalysts A new approach to performance issues. At present,
the discovery of non-metal catalysts is mainly focused on carbon materials doped
with impurity atoms.
4.6 Doped-CNT
Carbon nanotubes (CNTs), also known as Ba based tube, is a one-dimensional
quantum material with special structure (radial size is nanometer, axial size is micron,
and both ends of the tube are basically sealed) (see Fig. 4.39). CNTs were first discovered by Dr. Sumio Iijima [314], a scientist at NEC laboratory, in 1991 when he
observed the cathode deposits of arc evaporated graphite with high-resolution transmission electron microscope. He called the one-dimensional tubular nanostructured
carbon nanotubes. It is mainly composed of carbon atoms arranged in hexagon to
form coaxial tubes with several to dozens of layers. The fixed distance between layers
is about 0.34 nm, the diameter is generally from several nanometers to dozens of
nanometers, and the length can reach the order of micrometer or even millimeter. Tang
Zikang et al. [315] prepared single-walled carbon nanotubes with a diameter of only
0.4 nm in 2000, and prepared smaller single-walled carbon nanotubes with a diameter
of only 0.3 nm in 2008, which is the smallest one found at present [316]. The structure
of carbon nanotubes is curled into a cylindrical graphite sheet. Because the carbon
atoms in carbon nanotubes are SP
2 hybrid, compared with SP
3 hybrid, the S orbital
Y. Li et al.
of the volcano map, and its surface has the highest ORR activity. Among them, the
activity of chalcogenide of Rh is the same as that of Ru. The ORR activity of Rh
selenide is higher than its sulfide, which is consistent with experimental results [231].
Feng et al. [229] used XC-72 carbon powder as a carrier to prepare Co 3 S 4 and
CoSe 2 nanoparticles without using a surfactant. The obtained composite catalyst
particles are small and uniformly supported. In 0.5 M H 2 SO 4 solution, the on-set
potential of both catalysts can reach 0.7 V (vs. RHE). Nekooi et al. [232] used
microwave-assisted/polyol method to prepare CoSe nanoparticles with a particle
size of 8 nm on nanopore carbon. Its on-set potential reached 0.823 V (vs. SHE).
The calculated results according to the Koutecky–Levich equation indicate that the
reaction ORR process is a four-electron process. In addition, such materials are
resistant to methanol and formic acid.
4.5 Metal-Free Catalysts
The discovery and research of metal-free catalysts have opened up new approaches
and directions to replace precious metal oxygen reduction catalysts. The current
research results show that compared with metal-based catalysts, non-metallic oxygen
reduction catalysts have unparalleled advantages in terms of stability and anti-toxicity
performance, which is a solution to the current stability and anti-toxicity of metalbased oxygen reduction catalysts A new approach to performance issues. At present,
the discovery of non-metal catalysts is mainly focused on carbon materials doped
with impurity atoms.
4.6 Doped-CNT
Carbon nanotubes (CNTs), also known as Ba based tube, is a one-dimensional
quantum material with special structure (radial size is nanometer, axial size is micron,
and both ends of the tube are basically sealed) (see Fig. 4.39). CNTs were first discovered by Dr. Sumio Iijima [314], a scientist at NEC laboratory, in 1991 when he
observed the cathode deposits of arc evaporated graphite with high-resolution transmission electron microscope. He called the one-dimensional tubular nanostructured
carbon nanotubes. It is mainly composed of carbon atoms arranged in hexagon to
form coaxial tubes with several to dozens of layers. The fixed distance between layers
is about 0.34 nm, the diameter is generally from several nanometers to dozens of
nanometers, and the length can reach the order of micrometer or even millimeter. Tang
Zikang et al. [315] prepared single-walled carbon nanotubes with a diameter of only
0.4 nm in 2000, and prepared smaller single-walled carbon nanotubes with a diameter
of only 0.3 nm in 2008, which is the smallest one found at present [316]. The structure
of carbon nanotubes is curled into a cylindrical graphite sheet. Because the carbon
atoms in carbon nanotubes are SP
2 hybrid, compared with SP
3 hybrid, the S orbital