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Y. Li et al.
activity as Pt/C catalyst, and has better cathode selectivity, anti-toxic ability, and
stability than Pt/C.
Yao et al. [400] heat-treated the mixture of GO and I 2 at 500–1100 °C, XPS results
showed that I was I
3− and I
5− , and compared with Pt/C catalyst, I-graphene, as ORR
catalyst, had the same peak potential as Pt/C, but had a higher surface current density,
similar to N-graphene, I-graphene also showed cathode selectivity, good anti-toxic
ability, and good stability. In addition, the catalytic ORR process of I-graphene is
also a direct four-electron process.
The doping of impurity atoms will change or adjust the electronic structure of
graphene, which will change the structure and electronic properties of graphene.
The doped atoms can be divided into two categories: one is more valence electrons
than C atoms (such as N, P, S, I). This kind of doping will make the neighboring
C atoms produce positron effect, which can significantly promote the adsorption
and dissociation of oxygen on their surface; The other is the atom with less valence
electrons than the C atom (such as B). The atom doped into graphene will interact
with the large delocalization π bond of graphene to form the electron absorption
effect, while the position of B atom will promote the adsorption and dissociation of
oxygen on its surface.
4.6.6 Co-Doped Graphene
Co-doped graphene refers to the doped graphene formed by doping two or more
impurity atoms in the skeleton of graphene at the same time.
B- and N-doped graphene have many different physical and chemical properties.
B, N-graphene has different application prospects in many fields. Because the radii
of C, B, and N atoms are close to each other, the doping ratio and form of B and
N will have a great space to adjust. The electronic structures of B/N-graphene with
different composition and bonding form are different, which widens the application
fields of B/N-graphene. According to the different bonding, B, N-graphene can be
divided into two types: one is B and N are single-phase doped graphene (h-BCN);
the other is independent structure of h-BN (hexagonal born nitride) doped into the
skeleton of graphene (s-BCN).
For h-BCN, B atom and N atom are co-doped into the skeleton of graphene. The
extra electrons provided by N atom and the empty orbits provided by B atom are
combined into the conjugation system of C in graphene to change the electronic
structure of graphene and generate new electronic states, for example, to change the
density distribution of electronic states and increase the spin density of electrons
[375, 402]. For s-BCN, the neutral N-atom lone pair electrons and N-atom empty
orbits have no effect on the delocalization π bond of graphene. Because h-BN is not
conductive, s-BCN is equivalent to graphene with nanopores [403]. Therefore, the
ORR activity of s-BCN is only equivalent to that of graphene, in which h-BN is inert
to ORR, so when preparing B and N Co-doped graphene as ORR catalyst, s-BCN
should be avoided.
Y. Li et al.
activity as Pt/C catalyst, and has better cathode selectivity, anti-toxic ability, and
stability than Pt/C.
Yao et al. [400] heat-treated the mixture of GO and I 2 at 500–1100 °C, XPS results
showed that I was I
3− and I
5− , and compared with Pt/C catalyst, I-graphene, as ORR
catalyst, had the same peak potential as Pt/C, but had a higher surface current density,
similar to N-graphene, I-graphene also showed cathode selectivity, good anti-toxic
ability, and good stability. In addition, the catalytic ORR process of I-graphene is
also a direct four-electron process.
The doping of impurity atoms will change or adjust the electronic structure of
graphene, which will change the structure and electronic properties of graphene.
The doped atoms can be divided into two categories: one is more valence electrons
than C atoms (such as N, P, S, I). This kind of doping will make the neighboring
C atoms produce positron effect, which can significantly promote the adsorption
and dissociation of oxygen on their surface; The other is the atom with less valence
electrons than the C atom (such as B). The atom doped into graphene will interact
with the large delocalization π bond of graphene to form the electron absorption
effect, while the position of B atom will promote the adsorption and dissociation of
oxygen on its surface.
4.6.6 Co-Doped Graphene
Co-doped graphene refers to the doped graphene formed by doping two or more
impurity atoms in the skeleton of graphene at the same time.
B- and N-doped graphene have many different physical and chemical properties.
B, N-graphene has different application prospects in many fields. Because the radii
of C, B, and N atoms are close to each other, the doping ratio and form of B and
N will have a great space to adjust. The electronic structures of B/N-graphene with
different composition and bonding form are different, which widens the application
fields of B/N-graphene. According to the different bonding, B, N-graphene can be
divided into two types: one is B and N are single-phase doped graphene (h-BCN);
the other is independent structure of h-BN (hexagonal born nitride) doped into the
skeleton of graphene (s-BCN).
For h-BCN, B atom and N atom are co-doped into the skeleton of graphene. The
extra electrons provided by N atom and the empty orbits provided by B atom are
combined into the conjugation system of C in graphene to change the electronic
structure of graphene and generate new electronic states, for example, to change the
density distribution of electronic states and increase the spin density of electrons
[375, 402]. For s-BCN, the neutral N-atom lone pair electrons and N-atom empty
orbits have no effect on the delocalization π bond of graphene. Because h-BN is not
conductive, s-BCN is equivalent to graphene with nanopores [403]. Therefore, the
ORR activity of s-BCN is only equivalent to that of graphene, in which h-BN is inert
to ORR, so when preparing B and N Co-doped graphene as ORR catalyst, s-BCN
should be avoided.