4 Catalyst Materials for Oxygen Reduction Reaction
99
reduction electrocatalyst carriers [118, 119]. At present, CrN [120], TiN [[121], Ti x
Nb 1-x N [122, 123], VN [124], etc. as catalyst support materials loaded with Pt or Pd
have excellent catalytic performance and stability. For traditional carbon-supported
catalysts. Kumar et al. [125] reported that Nafion-modified Pt nanoparticles were
immobilized on the surface of TiN to form a Pt-TiN catalyst. The catalyst was tested
for oxygen reduction in a 0.5 mol·L
–1 H 3 PO 4 solution, showing a ratio of commercial Pt/C catalyst. Better electrochemical stability, durability, and higher electrocatalytic performance. Pan et al. [126] reported that the Pt/TiN NTs catalyst prepared
by depositing Pt nanoparticles on the surface of TiN nanotubes (TiN NTs) has far
better catalytic activity and stability than commercial Pt/C catalysts. Yang et al.
[120] reported that Pt nanoparticles were supported on the surface of mesoporous
CrN prepared by the solid–solid separation method, and the oxygen reduction and
charging catalytic performance of the prepared catalyst was far superior to that of
commercial Pt/C catalyst. Although the above-mentioned nitrides have such advantages as catalyst support materials, the nitrides face high synthesis temperatures
(mostly more than 1500 °C, even more than 2000 °C), small specific surface area,
large particle diameter, and dense active sites which causes problems such as low
current density, so in the future development, further research is needed by reducing
the synthesis temperature, increasing the specific surface area, and reducing the size
of the nanoparticles [118, 127, 128].
4.2 Novel Platinum-Based Catalyst
Membrane electrode assembly (MEA) is the core component of proton exchange
membrane fuel cells (PEMFCs), while cathode and anode catalysts in MEA are key
to determining MEA performance. From a catalytic point of view, Pt-based catalysts
are currently the best performing catalysts and used as catalysts for commercial
PEMFCs. Due to the high price of Pt and the scarcity of the earth’s reserves, the
commercial process of PEMFCs is greatly restricted. In particular, the cathode in
MEA has a slower kinetics of oxygen reduction reaction (ORR), resulting in more
requirement on catalyst performance. High requirements push up costs. At present,
the cost of catalysts accounts for 40–60% of the entire PEMFCs stack. Therefore,
the development of high-performance, low-cost ORR electrocatalysts has important
significance in the development of advanced, efficient, and low-cost PEMFCs, has a
crucial role to the large-scale commercialization of fuel cells. Current strategies to
reduce the cost of ORR catalysts include (1) reducing the use of Pt by optimizing
the utilization of Pt catalysts, (2) reducing the amount of Pt used by increasing the
intrinsic properties of Pt catalysts, and (3) developing inexpensive alternative catalyst
to Pt. The third strategy can theoretically solve the problem that the catalyst is subject
to Pt, but as far as the current research is concerned, these non-Pt catalysts have a
big gap on catalytic performance and practical application requirements. Therefore,
there is still a long distance on the commercialization of their applications.
99
reduction electrocatalyst carriers [118, 119]. At present, CrN [120], TiN [[121], Ti x
Nb 1-x N [122, 123], VN [124], etc. as catalyst support materials loaded with Pt or Pd
have excellent catalytic performance and stability. For traditional carbon-supported
catalysts. Kumar et al. [125] reported that Nafion-modified Pt nanoparticles were
immobilized on the surface of TiN to form a Pt-TiN catalyst. The catalyst was tested
for oxygen reduction in a 0.5 mol·L
–1 H 3 PO 4 solution, showing a ratio of commercial Pt/C catalyst. Better electrochemical stability, durability, and higher electrocatalytic performance. Pan et al. [126] reported that the Pt/TiN NTs catalyst prepared
by depositing Pt nanoparticles on the surface of TiN nanotubes (TiN NTs) has far
better catalytic activity and stability than commercial Pt/C catalysts. Yang et al.
[120] reported that Pt nanoparticles were supported on the surface of mesoporous
CrN prepared by the solid–solid separation method, and the oxygen reduction and
charging catalytic performance of the prepared catalyst was far superior to that of
commercial Pt/C catalyst. Although the above-mentioned nitrides have such advantages as catalyst support materials, the nitrides face high synthesis temperatures
(mostly more than 1500 °C, even more than 2000 °C), small specific surface area,
large particle diameter, and dense active sites which causes problems such as low
current density, so in the future development, further research is needed by reducing
the synthesis temperature, increasing the specific surface area, and reducing the size
of the nanoparticles [118, 127, 128].
4.2 Novel Platinum-Based Catalyst
Membrane electrode assembly (MEA) is the core component of proton exchange
membrane fuel cells (PEMFCs), while cathode and anode catalysts in MEA are key
to determining MEA performance. From a catalytic point of view, Pt-based catalysts
are currently the best performing catalysts and used as catalysts for commercial
PEMFCs. Due to the high price of Pt and the scarcity of the earth’s reserves, the
commercial process of PEMFCs is greatly restricted. In particular, the cathode in
MEA has a slower kinetics of oxygen reduction reaction (ORR), resulting in more
requirement on catalyst performance. High requirements push up costs. At present,
the cost of catalysts accounts for 40–60% of the entire PEMFCs stack. Therefore,
the development of high-performance, low-cost ORR electrocatalysts has important
significance in the development of advanced, efficient, and low-cost PEMFCs, has a
crucial role to the large-scale commercialization of fuel cells. Current strategies to
reduce the cost of ORR catalysts include (1) reducing the use of Pt by optimizing
the utilization of Pt catalysts, (2) reducing the amount of Pt used by increasing the
intrinsic properties of Pt catalysts, and (3) developing inexpensive alternative catalyst
to Pt. The third strategy can theoretically solve the problem that the catalyst is subject
to Pt, but as far as the current research is concerned, these non-Pt catalysts have a
big gap on catalytic performance and practical application requirements. Therefore,
there is still a long distance on the commercialization of their applications.