4 Catalyst Materials for Oxygen Reduction Reaction
97
The use of these materials not only reduces the amount of noble metal electrocatalyst,
but also improves the activity and stability of the catalyst.
4.1.2.1 Oxide
Metal oxides as electrocatalyst support materials can greatly improve the catalytic
activity and stability of electrocatalysts [97–100]. Popov et al. [101] used an electrode
prepared with Pt/TiO 2 as an electrocatalyst, and obtained a performance matching
that of commercial Pt/C. This is mainly due to the good mass transfer effect of Pt/TiO 2
electrocatalysts at high current densities. The Pt/TiO 2 electrocatalyst also exhibits a
high stability, which is mainly due to the strong metal interface force formed between
the Pt nanoparticles and TiO 2 in the Pt/TiO 2 electrocatalyst. Adzic et al. [102] first
prepared niobium oxide by aerogel method, and then deposited monodispersed Pt
nanoparticles on the carbon-supported niobium oxide surface to form Pt/NbO 2 /C
composites. The composite exhibits oxygen reduction performance, and its mass
specific activity is three times that of Pt/C. This is mainly due to the reduced OH
adsorption, which is caused by the side repulsion between PtOH and the surface sites
of the oxide. Sun et al. [103] deposited Pt nanoparticles on the surface of carbon paper
directly grown SnO 2 nanowires by electrochemical deposition. The performance of
the oxygen reduction electrocatalyst prepared by this method is higher than that of
standard Pt/C catalysts. Kulesza et al. [104] reported that carbon-supported RuSex
nanoparticles were coated with a layer of WO 3 film, and then the oxygen reduction
electrocatalytic performance was enhanced under acidic conditions. The coated WO 3
thin film is favorable for the decomposition of the intermediate H 2 O 2 , so that the
entire reduction process is mainly performed by a four-electron process.
4.1.2.2 Carbide
Since the discovery of transition metal carbides with platinum-like electrocatalytic
properties in the 1870s [105], carbides have received widespread attention [106–109].
This is due to the fact that transition metal carbides, especially tungsten carbides, have
similar Fermi levels and electron cloud densities to platinum. Therefore, the carbide
itself has certain oxygen reduction electrocatalytic performance, and as a catalyst
support material, it can also improve catalytic activity through synergy [106–109].
In addition, carbides also have a variety of chemical properties, so they are more
interesting to researchers as electrocatalysts. Tungsten carbide is one of the most
studied materials in carbide, because it still has high stability, good conductivity,
and high activity under acidic conditions. Therefore, tungsten carbide is also widely
used as an electrocatalytic support material to synergistically enhance the oxygen
reduction performance of the catalyst [106–110]. For example, Shen et al. [109]
directly deposited platinum nanoparticles on the surface of carbon-supported tungsten carbide to form a Pt-WC/C catalyst, and its oxygen reduction electrocatalytic
performance was far better than that obtained by direct physical mixing of WC and
97
The use of these materials not only reduces the amount of noble metal electrocatalyst,
but also improves the activity and stability of the catalyst.
4.1.2.1 Oxide
Metal oxides as electrocatalyst support materials can greatly improve the catalytic
activity and stability of electrocatalysts [97–100]. Popov et al. [101] used an electrode
prepared with Pt/TiO 2 as an electrocatalyst, and obtained a performance matching
that of commercial Pt/C. This is mainly due to the good mass transfer effect of Pt/TiO 2
electrocatalysts at high current densities. The Pt/TiO 2 electrocatalyst also exhibits a
high stability, which is mainly due to the strong metal interface force formed between
the Pt nanoparticles and TiO 2 in the Pt/TiO 2 electrocatalyst. Adzic et al. [102] first
prepared niobium oxide by aerogel method, and then deposited monodispersed Pt
nanoparticles on the carbon-supported niobium oxide surface to form Pt/NbO 2 /C
composites. The composite exhibits oxygen reduction performance, and its mass
specific activity is three times that of Pt/C. This is mainly due to the reduced OH
adsorption, which is caused by the side repulsion between PtOH and the surface sites
of the oxide. Sun et al. [103] deposited Pt nanoparticles on the surface of carbon paper
directly grown SnO 2 nanowires by electrochemical deposition. The performance of
the oxygen reduction electrocatalyst prepared by this method is higher than that of
standard Pt/C catalysts. Kulesza et al. [104] reported that carbon-supported RuSex
nanoparticles were coated with a layer of WO 3 film, and then the oxygen reduction
electrocatalytic performance was enhanced under acidic conditions. The coated WO 3
thin film is favorable for the decomposition of the intermediate H 2 O 2 , so that the
entire reduction process is mainly performed by a four-electron process.
4.1.2.2 Carbide
Since the discovery of transition metal carbides with platinum-like electrocatalytic
properties in the 1870s [105], carbides have received widespread attention [106–109].
This is due to the fact that transition metal carbides, especially tungsten carbides, have
similar Fermi levels and electron cloud densities to platinum. Therefore, the carbide
itself has certain oxygen reduction electrocatalytic performance, and as a catalyst
support material, it can also improve catalytic activity through synergy [106–109].
In addition, carbides also have a variety of chemical properties, so they are more
interesting to researchers as electrocatalysts. Tungsten carbide is one of the most
studied materials in carbide, because it still has high stability, good conductivity,
and high activity under acidic conditions. Therefore, tungsten carbide is also widely
used as an electrocatalytic support material to synergistically enhance the oxygen
reduction performance of the catalyst [106–110]. For example, Shen et al. [109]
directly deposited platinum nanoparticles on the surface of carbon-supported tungsten carbide to form a Pt-WC/C catalyst, and its oxygen reduction electrocatalytic
performance was far better than that obtained by direct physical mixing of WC and