Nickel and nitrogen co-doped carbon (Ni–N–C) has emerged as a promising catalyst for the CO 2 reduction reaction (CO 2 RR); however, the chemical nature of its active sites has remained elusive. Herein, we report the exploration of the reactivity and active sites of Ni–N–C for the CO 2 RR. Single atom Ni coordinated with N confined in a carbon matrix was prepared through thermal activation of chemically Ni-doped zeolitic imidazolate frameworks (ZIFs) and directly visualized by aberration-corrected scanning transmission electron microscopy. Electrochemical results show the enhanced intrinsic reactivity and selectivity of Ni–N sites for the reduction of CO 2 to CO, delivering a maximum CO faradaic efficiency of 96% at a low overpotential of 570 mV. Density functional theory (DFT) calculations predict that the edge-located Ni–N 2+2 sites with dangling bond-containing carbon atoms are the active sites facilitating the dissociation of the C–O bond of the *COOH intermediate, while bulk-hosted Ni–N 4 is kinetically inactive. Furthermore, the high capability of edge-located Ni–N 4 being able to thermodynamically suppress the competitive hydrogen evolution is also explained. The proposal of edge-hosed Ni–N 2+2 sites provides new insight into designing high-efficiency Ni–N–C for CO 2 reduction.
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A MOF-derived Co 3 O 4 /nitrogen-doped carbon composite for chlorine-assisted production of ethylene oxide
Ethylene oxide (EO) is one of the most crucial materials in plastic industries. The traditional catalytic process requires high temperature and pressure to produce EO. A chlorine-assisted system has been reported to produce EO, but it required noble metal catalysts, which significantly increased the cost. In this work, a MOF-derived Co 3 O 4 /nitrogen-doped carbon composite (Co 3 O 4 /NC) prepared through a two-step calcination method exhibited remarkable chlorine evolution reaction (ClER) activity as compared with a commercial RuO 2 catalyst, which can be attributed to the higher specific surface area and lower resistance of its porous structure and nitrogen-doped carbon. Furthermore, the Co 3 O 4 /NC maintained a stable potential and a high faradaic efficiency throughout the 10-hour electrolysis test.
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- Award ID(s):
- 2132200
- NSF-PAR ID:
- 10408532
- Date Published:
- Journal Name:
- Green Chemistry
- Volume:
- 25
- Issue:
- 5
- ISSN:
- 1463-9262
- Page Range / eLocation ID:
- 1982 to 1990
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2GC04508G
