Metal-free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting
Metal-free carbon catalysts have attracted great interest because of their high electrical conductivity, tailorable porosity and surface area, affordability, and sustainability. In particular, their bifunctional activity for hydrogen and oxygen evolution reactions (HER and OER) is attractive for ele...
| Main Authors: | , , , , , , , , , |
|---|---|
| Other Authors: | |
| Format: | Journal Article |
| Language: | English |
| Published: |
2020
|
| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/139235 |
| _version_ | 1811690492441657344 |
|---|---|
| author | Lei, Yaojie Wei, Li Zhai, Shengli Wang, Yanqing Karahan, H. Enis Chen, Xuncai Zhou, Zheng Wang, Chaojun Sui, Xiao Chen, Yuan |
| author2 | School of Chemical and Biomedical Engineering |
| author_facet | School of Chemical and Biomedical Engineering Lei, Yaojie Wei, Li Zhai, Shengli Wang, Yanqing Karahan, H. Enis Chen, Xuncai Zhou, Zheng Wang, Chaojun Sui, Xiao Chen, Yuan |
| author_sort | Lei, Yaojie |
| collection | NTU |
| description | Metal-free carbon catalysts have attracted great interest because of their high electrical conductivity, tailorable porosity and surface area, affordability, and sustainability. In particular, their bifunctional activity for hydrogen and oxygen evolution reactions (HER and OER) is attractive for electrochemical splitting of water. However, pristine carbon materials have low activities for HER/OER. Here, a high-performance carbon electrocatalyst is demonstrated by first pyrolyzing a metal-organic framework (MOF), i.e., zeolitic imidazolate framework-8 (ZIF-8), followed by optimized cathodic polarization treatment (CPT). Pyrolyzing ZIF-8 produces a highly N-doped (8.4 at%) carbon material having a large specific surface area of 1017 m2 g1 with micro and mesopores. CPT in 0.5 M H2SO4 for up to 8 hours modulates the composition of N- and O-containing surface functional groups of the pyrolyzed ZIF-8 without sacrificing its large surface area and pore size distribution. After the 6-hour CPT, this material shows an excellent HER activity in 0.5 M H2SO4 electrolyte with an overpotential of 155 mV, a Tafel slope of 54.7 mV dec1, and an exchange current density of 0.063 mA cm2. And the 4-hour CPT results in excellent OER activity in 0.1 M KOH electrolyte with an overpotential of 476 mV and a Tafel slope of 78.5 mV dec1. In a demonstration, these two carbon electrocatalysts steadily run a two-electrode water electrolyzer at a current density of 10 mA cm2 over 8 hours under a potential of 1.82 V with a Faradaic efficiency of 98.0-99.1% in 0.1 M KOH electrolyte. The superior activity of the designed carbon electrocatalysts can be attributed to the functional group composition modulation achieved by CPT. High-performance metal-free carbon electrocatalysts derived from MOFs show excellent potentials for energy and environmental applications. |
| first_indexed | 2024-10-01T06:04:51Z |
| format | Journal Article |
| id | ntu-10356/139235 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T06:04:51Z |
| publishDate | 2020 |
| record_format | dspace |
| spelling | ntu-10356/1392352020-05-18T06:17:30Z Metal-free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting Lei, Yaojie Wei, Li Zhai, Shengli Wang, Yanqing Karahan, H. Enis Chen, Xuncai Zhou, Zheng Wang, Chaojun Sui, Xiao Chen, Yuan School of Chemical and Biomedical Engineering Engineering::Chemical engineering Water Splitting Electrocatalysts Metal-free carbon catalysts have attracted great interest because of their high electrical conductivity, tailorable porosity and surface area, affordability, and sustainability. In particular, their bifunctional activity for hydrogen and oxygen evolution reactions (HER and OER) is attractive for electrochemical splitting of water. However, pristine carbon materials have low activities for HER/OER. Here, a high-performance carbon electrocatalyst is demonstrated by first pyrolyzing a metal-organic framework (MOF), i.e., zeolitic imidazolate framework-8 (ZIF-8), followed by optimized cathodic polarization treatment (CPT). Pyrolyzing ZIF-8 produces a highly N-doped (8.4 at%) carbon material having a large specific surface area of 1017 m2 g1 with micro and mesopores. CPT in 0.5 M H2SO4 for up to 8 hours modulates the composition of N- and O-containing surface functional groups of the pyrolyzed ZIF-8 without sacrificing its large surface area and pore size distribution. After the 6-hour CPT, this material shows an excellent HER activity in 0.5 M H2SO4 electrolyte with an overpotential of 155 mV, a Tafel slope of 54.7 mV dec1, and an exchange current density of 0.063 mA cm2. And the 4-hour CPT results in excellent OER activity in 0.1 M KOH electrolyte with an overpotential of 476 mV and a Tafel slope of 78.5 mV dec1. In a demonstration, these two carbon electrocatalysts steadily run a two-electrode water electrolyzer at a current density of 10 mA cm2 over 8 hours under a potential of 1.82 V with a Faradaic efficiency of 98.0-99.1% in 0.1 M KOH electrolyte. The superior activity of the designed carbon electrocatalysts can be attributed to the functional group composition modulation achieved by CPT. High-performance metal-free carbon electrocatalysts derived from MOFs show excellent potentials for energy and environmental applications. 2020-05-18T06:17:30Z 2020-05-18T06:17:30Z 2017 Journal Article Lei, Y., Wei, L., Zhai, S., Wang, Y., Karahan, H. E., Chen, X., . . . Chen, Y. (2018). Metal-free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting. Materials Chemistry Frontiers, 2(1), 102-111. doi:10.1039/C7QM00452D 2052-1537 https://hdl.handle.net/10356/139235 10.1039/C7QM00452D 2-s2.0-85050913486 1 2 102 111 en Materials Chemistry Frontiers © 2018 The Royal Society of Chemistry and the Chinese Chemical Society. All rights reserved. |
| spellingShingle | Engineering::Chemical engineering Water Splitting Electrocatalysts Lei, Yaojie Wei, Li Zhai, Shengli Wang, Yanqing Karahan, H. Enis Chen, Xuncai Zhou, Zheng Wang, Chaojun Sui, Xiao Chen, Yuan Metal-free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting |
| title | Metal-free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting |
| title_full | Metal-free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting |
| title_fullStr | Metal-free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting |
| title_full_unstemmed | Metal-free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting |
| title_short | Metal-free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting |
| title_sort | metal free bifunctional carbon electrocatalysts derived from zeolitic imidazolate frameworks for efficient water splitting |
| topic | Engineering::Chemical engineering Water Splitting Electrocatalysts |
| url | https://hdl.handle.net/10356/139235 |
| work_keys_str_mv | AT leiyaojie metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting AT weili metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting AT zhaishengli metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting AT wangyanqing metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting AT karahanhenis metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting AT chenxuncai metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting AT zhouzheng metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting AT wangchaojun metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting AT suixiao metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting AT chenyuan metalfreebifunctionalcarbonelectrocatalystsderivedfromzeoliticimidazolateframeworksforefficientwatersplitting |