4 Catalyst Materials for Oxygen Reduction Reaction
123
4.3.3 Graphene and Doped Graphene ORR Co-Catalyst
Graphene is a single-layer graphite sheet that was first discovered in 2004 by Andre
Geim and Konstantin Novoselov at University of Manchester, UK [224]. Graphene
will form a large delocalized π bond in a two-dimensional plane, making graphene
have many peculiar mechanical [145–147] and electronic properties [148–150], such
as charge carriers(electrons or holes) have a static mass of zero, and their charge
carriers have a high transmission rate in honeycomb crystals of graphene, which can
reach three thousandths of the speed of light [151, 152]. These peculiar properties
have attracted a large number of scientific and technological workers to study it. For
example, people are looking forward to using graphene as a substrate to prepare highspeed nanoelectronic devices. In addition, by changing the stacking or modification
of graphene, the band gap, carrier type, and carrier concentration of graphene can
be adjusted [153]. These unique properties make graphene a very broad application
prospect [154–156].
American scientist Dai et al. reported that graphene and its supported nanoparticles have close bonding and synergistic coupling effects, which further improved
the oxygen reduction activity of graphene-based composites [158, 159]. The fast
electron power provided by graphene can significantly promote the reaction rate and
efficiency of ORR in fuel cells [160]. Shao et al. [161] prepared Pt/GNP and Pt/CNT
by depositing Pt nanoparticles on PDDA-modified graphene nanoplatelets (GNP)
and CNT. The stability of Pt/GNP is better than Pt/CNT and is 2–3 times better than
commercial Pt/C catalyst. They believe that the stability of Pt/GNP results from the
high degree of graphitization of GNP and the interaction between Pt and GNP. He
et al. [162] loaded Pt nanoparticles on Graphene Quantum Dots (GQDs), and the
results confirmed that such GQDs can promote the ORR activity of Pt. They believe
that this promotion is due to the fact that defects on GQDs can not only reduce the
activation energy of O 2 molecular dissociation through electron transfer between Pt
and O 2 , but also reduce the energy barrier of this rate-determining step by weakening the binding of HO*. The close relationship between the graphene support and
Pt nanoparticles changes the d-band center of Pt, and changes the charge transport
kinetics in the ORR process, and thus promotes the ORR activity of Pt [163].
In graphene, the doping of impurity atoms introduced into the framework will
change its electronic characteristics and can adjust the band structure of graphene
materials [164]. This change in electronic properties and energy bands will greatly
change the original properties of grapheme [165]. Bai et al. [166] found that the
catalyst formed by supporting Pt with nitrogen-doped graphene can improve its ORR
performance in both acid and alkali medium. Vinayan et al. [167] reported that after
nitrogen-doped graphene was loaded with Pt (Pt/N-HEG) and PtCo alloy (Pt 3 Co/NHEG) nanoparticles. The Pt/N-HEG catalyst can achieve a power density of 512
mW cm
−2 , which is more than twice that of commercial Pt/C (241 mW cm
−2 ). The
maximum power density of Pt 3 Co/N-HEG reaches 805 mW cm
−2 , which is more
than 3 times that of commercial Pt/C.
123
4.3.3 Graphene and Doped Graphene ORR Co-Catalyst
Graphene is a single-layer graphite sheet that was first discovered in 2004 by Andre
Geim and Konstantin Novoselov at University of Manchester, UK [224]. Graphene
will form a large delocalized π bond in a two-dimensional plane, making graphene
have many peculiar mechanical [145–147] and electronic properties [148–150], such
as charge carriers(electrons or holes) have a static mass of zero, and their charge
carriers have a high transmission rate in honeycomb crystals of graphene, which can
reach three thousandths of the speed of light [151, 152]. These peculiar properties
have attracted a large number of scientific and technological workers to study it. For
example, people are looking forward to using graphene as a substrate to prepare highspeed nanoelectronic devices. In addition, by changing the stacking or modification
of graphene, the band gap, carrier type, and carrier concentration of graphene can
be adjusted [153]. These unique properties make graphene a very broad application
prospect [154–156].
American scientist Dai et al. reported that graphene and its supported nanoparticles have close bonding and synergistic coupling effects, which further improved
the oxygen reduction activity of graphene-based composites [158, 159]. The fast
electron power provided by graphene can significantly promote the reaction rate and
efficiency of ORR in fuel cells [160]. Shao et al. [161] prepared Pt/GNP and Pt/CNT
by depositing Pt nanoparticles on PDDA-modified graphene nanoplatelets (GNP)
and CNT. The stability of Pt/GNP is better than Pt/CNT and is 2–3 times better than
commercial Pt/C catalyst. They believe that the stability of Pt/GNP results from the
high degree of graphitization of GNP and the interaction between Pt and GNP. He
et al. [162] loaded Pt nanoparticles on Graphene Quantum Dots (GQDs), and the
results confirmed that such GQDs can promote the ORR activity of Pt. They believe
that this promotion is due to the fact that defects on GQDs can not only reduce the
activation energy of O 2 molecular dissociation through electron transfer between Pt
and O 2 , but also reduce the energy barrier of this rate-determining step by weakening the binding of HO*. The close relationship between the graphene support and
Pt nanoparticles changes the d-band center of Pt, and changes the charge transport
kinetics in the ORR process, and thus promotes the ORR activity of Pt [163].
In graphene, the doping of impurity atoms introduced into the framework will
change its electronic characteristics and can adjust the band structure of graphene
materials [164]. This change in electronic properties and energy bands will greatly
change the original properties of grapheme [165]. Bai et al. [166] found that the
catalyst formed by supporting Pt with nitrogen-doped graphene can improve its ORR
performance in both acid and alkali medium. Vinayan et al. [167] reported that after
nitrogen-doped graphene was loaded with Pt (Pt/N-HEG) and PtCo alloy (Pt 3 Co/NHEG) nanoparticles. The Pt/N-HEG catalyst can achieve a power density of 512
mW cm
−2 , which is more than twice that of commercial Pt/C (241 mW cm
−2 ). The
maximum power density of Pt 3 Co/N-HEG reaches 805 mW cm
−2 , which is more
than 3 times that of commercial Pt/C.