138
Y. Li et al.
times. In addition, the incorporation of P can also change the pathway of ORR.
Their research results show that the yield of H 2 O 2 in the ORR process of Co-PNC
is less than 4%, while the H 2 O 2 production of P-doped Co–N-C material can reach
10%. Zhu et al. [222] prepared a quaternary Co–N–P–C oxygen reduction catalyst
by a one-step method using a cheap aminophosphonic acid chelate resin. They used
aminophosphonic acid chelate resin. A simple heat treatment with a mixture of cobalt
chloride gave a quaternary Co–N–P–C oxygen reduction catalyst. Compared with
Co–N–C and non-metallic N–P–C in 0.1 M HClO 4 solution, Co–N–P–C showed
better ORR activity and showed good stability.
According to the current research on Me-P–C (M = Fe, Co, Ni)-based catalysts,
there is currently research on the characterization of ORR performance of half-cells,
and there is still no research on its characterization in full-cells in fuel cells. Moreover,
related research is mainly concentrated in alkaline media. Although it has been also
reported in acidic media [221], compared with the more in-depth studies of Me-N–
C(M = Fe, Co, Ni)-based catalysts, there is still a gap between them. Because the
ORR performance of this non-noble metal catalyst has a great relationship with its
preparation technology, material structure, chemical composition and other factors,
Me-P–C (M = Fe, Co, Ni)-based catalysts still need to be systematically researched
to develop higher performance Me-P–C (M = Fe, Co, Ni)-based catalysts. In short,
the research on Me-P–C (M = Fe, Co, Ni)-based catalysts has great developing space
and potential.
4.4.3.3 Transition Metal Oxide ORR Catalyst
People have been studying the catalytic effect of metal oxides on oxygen reduction.
In alkaline media, it has been found that on the surface of Nafion-modified Au
electrodes (without MnO x ), the reduction of O 2 is a two-electron process, and the
product produced is HO 2
− . In the presence of MnO x (including Mn 2 O 3 , Mn 3 O 4 ,
Mn 5 O 8 , and MnOOH), the current density of first reduction peak of O 2 reduction
on the surface of the Nafion-modified Au electrode significantly increased, while
the reduction peak current of HO 2
− further reduced to of OH
− . And the process of
O 2 reduction changes from a two-electron process to a four-electron process, which
indicates that MnO x has the catalytic activity to further reduce HO 2
− to OH
− [183].
Gorlin et al. [182] prepared MnO x (MnO, Mn 3 O 4 , Mn 2 O 3 , and MnO 2 ) nanoparticles
by sputtering and selectively deposited them on a glassy carbon substrate (GC)
(see Fig. 4.37). In a variety of MnO x /GC and MnO x /pGC (pGC is porous GC)
catalysts, 14 nm-sized MnO particles are supported on the pGC carrier compared to
the GC. In addition to the increased diffusion limit current, its on-set potential was not
improved. When MnO nanoparticles are transformed into Mn 3 O 4 nanoparticles, the
oxygen reduction catalytic activity of Mn 3 O 4 /pGC is greatly improved, and its on-set
potential is increased to 0.8 V(vs. RHE), and the ORR process becomes completely
four-electron process. The specific and mass activities at 0.75 V (vs. RHE) reached
3700 μA·cm
–2
cat and 3100 A·g
–1
cat .
Y. Li et al.
times. In addition, the incorporation of P can also change the pathway of ORR.
Their research results show that the yield of H 2 O 2 in the ORR process of Co-PNC
is less than 4%, while the H 2 O 2 production of P-doped Co–N-C material can reach
10%. Zhu et al. [222] prepared a quaternary Co–N–P–C oxygen reduction catalyst
by a one-step method using a cheap aminophosphonic acid chelate resin. They used
aminophosphonic acid chelate resin. A simple heat treatment with a mixture of cobalt
chloride gave a quaternary Co–N–P–C oxygen reduction catalyst. Compared with
Co–N–C and non-metallic N–P–C in 0.1 M HClO 4 solution, Co–N–P–C showed
better ORR activity and showed good stability.
According to the current research on Me-P–C (M = Fe, Co, Ni)-based catalysts,
there is currently research on the characterization of ORR performance of half-cells,
and there is still no research on its characterization in full-cells in fuel cells. Moreover,
related research is mainly concentrated in alkaline media. Although it has been also
reported in acidic media [221], compared with the more in-depth studies of Me-N–
C(M = Fe, Co, Ni)-based catalysts, there is still a gap between them. Because the
ORR performance of this non-noble metal catalyst has a great relationship with its
preparation technology, material structure, chemical composition and other factors,
Me-P–C (M = Fe, Co, Ni)-based catalysts still need to be systematically researched
to develop higher performance Me-P–C (M = Fe, Co, Ni)-based catalysts. In short,
the research on Me-P–C (M = Fe, Co, Ni)-based catalysts has great developing space
and potential.
4.4.3.3 Transition Metal Oxide ORR Catalyst
People have been studying the catalytic effect of metal oxides on oxygen reduction.
In alkaline media, it has been found that on the surface of Nafion-modified Au
electrodes (without MnO x ), the reduction of O 2 is a two-electron process, and the
product produced is HO 2
− . In the presence of MnO x (including Mn 2 O 3 , Mn 3 O 4 ,
Mn 5 O 8 , and MnOOH), the current density of first reduction peak of O 2 reduction
on the surface of the Nafion-modified Au electrode significantly increased, while
the reduction peak current of HO 2
− further reduced to of OH
− . And the process of
O 2 reduction changes from a two-electron process to a four-electron process, which
indicates that MnO x has the catalytic activity to further reduce HO 2
− to OH
− [183].
Gorlin et al. [182] prepared MnO x (MnO, Mn 3 O 4 , Mn 2 O 3 , and MnO 2 ) nanoparticles
by sputtering and selectively deposited them on a glassy carbon substrate (GC)
(see Fig. 4.37). In a variety of MnO x /GC and MnO x /pGC (pGC is porous GC)
catalysts, 14 nm-sized MnO particles are supported on the pGC carrier compared to
the GC. In addition to the increased diffusion limit current, its on-set potential was not
improved. When MnO nanoparticles are transformed into Mn 3 O 4 nanoparticles, the
oxygen reduction catalytic activity of Mn 3 O 4 /pGC is greatly improved, and its on-set
potential is increased to 0.8 V(vs. RHE), and the ORR process becomes completely
four-electron process. The specific and mass activities at 0.75 V (vs. RHE) reached
3700 μA·cm
–2
cat and 3100 A·g
–1
cat .