TY - JOUR
T1 - Electrochemical and spectroscopic study of novel Cu and Fe-based catalysts for oxygen reduction in alkaline media
AU - He, Qinggang
AU - Yang, Xiaofang
AU - He, Ruihua
AU - Bueno-López, Agustín
AU - Miller, Hamish
AU - Ren, Xiaoming
AU - Yang, Wanli
AU - Koel, Bruce E.
N1 - Funding Information:
This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Hydrogen, Fuel Cells and Infrastructure Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. BEK acknowledges support by the National Science Foundation under Grant No. CHE-1129417 .
PY - 2012/9/1
Y1 - 2012/9/1
N2 - We synthesized two "single-core" Fe-N x/C and Cu-N x/C electrocatalysts and a bi-core CuFe-N x/C composite electrocatalyst using iron and copper phthalocyanine-based precursors and a high-temperature pyrolysis method. The morphology, structure, and activity toward the oxygen reduction reaction (ORR) in alkaline media were evaluated for each electrocatalyst by transmission electron microscopy (TEM), X-ray Diffraction (XRD), and the rotating ring-disk electrode (RRDE) method. Although the Cu-N x/C catalyst showed lower catalytic activity than Fe-N x/C, the presence of Cu enhanced the ORR performance of bi-core CuFe-N x/C, as compared to single-core Fe-N x/C. To fully understand the synergistic effect between Cu and Fe on this enhancement, high resolution X-ray photoelectron spectroscopy (HR-XPS) and soft X-ray absorption spectroscopy (XAS) was employed to study the electronic structure of as-synthesized electrocatalysts. The HR-XPS analysis showed that metal-nitrogen bonding was maintained and that the oxidation states of Fe and Cu were influenced by the presence of the second metal in the bi-core catalyst. The XAS data revealed that a fraction of an electron was transferred from Fe to Cu, which may help to lower the kinetic barrier during the ORR process. Based on our experimental results and four different models, we briefly discuss ORR mechanisms on these metallic catalysts.
AB - We synthesized two "single-core" Fe-N x/C and Cu-N x/C electrocatalysts and a bi-core CuFe-N x/C composite electrocatalyst using iron and copper phthalocyanine-based precursors and a high-temperature pyrolysis method. The morphology, structure, and activity toward the oxygen reduction reaction (ORR) in alkaline media were evaluated for each electrocatalyst by transmission electron microscopy (TEM), X-ray Diffraction (XRD), and the rotating ring-disk electrode (RRDE) method. Although the Cu-N x/C catalyst showed lower catalytic activity than Fe-N x/C, the presence of Cu enhanced the ORR performance of bi-core CuFe-N x/C, as compared to single-core Fe-N x/C. To fully understand the synergistic effect between Cu and Fe on this enhancement, high resolution X-ray photoelectron spectroscopy (HR-XPS) and soft X-ray absorption spectroscopy (XAS) was employed to study the electronic structure of as-synthesized electrocatalysts. The HR-XPS analysis showed that metal-nitrogen bonding was maintained and that the oxidation states of Fe and Cu were influenced by the presence of the second metal in the bi-core catalyst. The XAS data revealed that a fraction of an electron was transferred from Fe to Cu, which may help to lower the kinetic barrier during the ORR process. Based on our experimental results and four different models, we briefly discuss ORR mechanisms on these metallic catalysts.
KW - Alkaline fuel cell
KW - Cu
KW - Fe
KW - Non-noble electrocatalyst
KW - Oxygen reduction reaction
KW - X-ray absorption spectroscopy
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U2 - 10.1016/j.jpowsour.2012.04.029
DO - 10.1016/j.jpowsour.2012.04.029
M3 - Article
AN - SCOPUS:84860819267
SN - 0378-7753
VL - 213
SP - 169
EP - 179
JO - Journal of Power Sources
JF - Journal of Power Sources
ER -