Volume 16, Issue 15 e202400017
Research Article

Cu, Fe, N-doped Carbon Nanotubes Prepared through Silica Coating for Selective Oxygen Reduction to Water in Acidic Media

Dr. Masaru Kato

Corresponding Author

Dr. Masaru Kato

Faculty of Environmental Earth Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

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Daiki Abe

Daiki Abe

Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

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Siqi Xie

Siqi Xie

Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

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Shun Sato

Shun Sato

Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

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Natsuki Fujibayashi

Natsuki Fujibayashi

Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

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Dr. Koki Matsumoto

Dr. Koki Matsumoto

Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, 565-0871 Japan

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Prof. Akira Onoda

Prof. Akira Onoda

Faculty of Environmental Earth Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

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Prof. Takashi Hayashi

Prof. Takashi Hayashi

Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, 565-0871 Japan

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Dr. Takaya Mitsui

Dr. Takaya Mitsui

Foundational Quantum Technology Research Directorate, National Institute for Quantum Science and Technology, Sayo, Hyogo, 679-5148 Japan

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Dr. Kosuke Fujiwara

Dr. Kosuke Fujiwara

Foundational Quantum Technology Research Directorate, National Institute for Quantum Science and Technology, Sayo, Hyogo, 679-5148 Japan

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Dr. Takashi Yamamoto

Dr. Takashi Yamamoto

Department of Chemistry, Keio University, 3-14-1 Hiyoshi, Yokohama, 223-8522 Japan

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Prof. Yasuaki Einaga

Prof. Yasuaki Einaga

Department of Chemistry, Keio University, 3-14-1 Hiyoshi, Yokohama, 223-8522 Japan

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Dr. Colin A. Tadgell

Dr. Colin A. Tadgell

Faculty of Environmental Earth Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

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Yuta Kato

Yuta Kato

Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

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Prof. Kiyotaka Asakura

Prof. Kiyotaka Asakura

Institute for Catalysis, Hokkaido University, N21 W10, Kita-ku, Sapporo, 001-0021 Japan

Ritsumeikan SR Center, Ritsumeikan University, Kusatsu, 525-8577 Japan

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Prof. Ichizo Yagi

Corresponding Author

Prof. Ichizo Yagi

Faculty of Environmental Earth Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo, 060-0810 Japan

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First published: 22 April 2024
Citations: 1

Graphical Abstract

Cu, Fe, N-doped carbon nanotubes, (Cu,Fe)−N−CNT, was prepared using a silica coating method as electrocatalysts for the oxygen reduction reaction (ORR) in acidic media. (Cu,Fe)−N−CNT shows H2O2 yields of <1 % for the ORR. Physicochemical measurements reveal that bimetallic doping gives an impact on kinetic parameters rather than thermodynamic ones.

Abstract

We report Cu, Fe, N-doped carbon nanotubes, (Cu,Fe)−N−CNT, as electrocatalysts for the oxygen reduction reaction (ORR) in acidic media. (Cu,Fe)−N−CNT was prepared using a silica coating method in pyrolysis to minimize the formation of carbon-coated metal oxide or carbide nanoparticles, which are known to be inactive for the H2O2 reduction. (Cu,Fe)−N−CNT shows a turnover frequency of 0.66 e site−1 s−1 at +0.8 V vs. RHE and H2O2 yields of <1 % for the ORR with a utilization factor of active sites of 82 %. Kinetic analysis reveals that 4e transfer rates for (Cu,Fe)−N−CNT are higher than those of a monometallic counterpart of Fe−N−CNT. In situ X-ray absorption spectroscopy enables us to determine redox potentials: E°’(FeIII/FeII)=0.65 V vs. RHE and E°’(CuII/CuI)=0.45 V for (Cu,Fe)−N−CNT, and E°’(FeIII/FeII)=0.65 V for Fe−N−CNT. These results indicate that bimetallic doping into carbon nanotubes gives the effect on kinetic parameters but not on thermodynamic ones. In other words, there is no direct electronic interactions between the Cu and Fe active sites for (Cu,Fe)-N-CNT because such interactions should modulate their redox potentials.

Conflict of interests

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available in the supplementary material of this article.