# Single-atom catalysts: one metal atom, four nitrogens

> A single-atom catalyst spreads its metal as isolated atoms, each held by nitrogen in a carbon sheet, so every metal atom can be an active site. Pyrolysing a bimetallic Zn/Co framework does it: the linker turns into N-doped carbon, zinc evaporates above 800 °C, and cobalt stays behind as single atoms that reduce oxygen better than commercial platinum on carbon.

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- Updated: 2026-10-14
- Category: Electrocatalysis
- Method: Single-atom catalysis
- Starting materials: A bimetallic Zn/Co zeolitic imidazolate framework (ZIF)
- Product: Co single atoms on N-doped porous carbon, over 4 wt% Co (Yin et al. 2016)
- Key result: Atomic dispersion confirmed by aberration-corrected electron microscopy and EXAFS (Yin et al. 2016). Share of surface atoms computed for cuboctahedral clusters; ORR curves computed with the paper’s half-wave potentials, shapes illustrative
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## Steps

1. **Framework**: Co mixed into a zinc imidazolate framework: the metals start apart, on the framework nodes
2. **Pyrolysis**: Carbonizing the linker reduces Co; above 800 °C the Zn evaporates (Yin et al. 2016)
3. **Single atoms**: Co stays as isolated atoms held by N in porous carbon, seen by aberration-corrected microscopy and EXAFS
4. **Activity**: ORR half-wave potential 0.881 V, more positive than commercial Pt/C (0.811 V) in the same study
5. **Stability**: The single atoms resisted sintering at 900 °C (Yin et al. 2016)

## Strengths

- Every metal atom can be a site
- Cheap metals (Co, Fe) instead of Pt
- Well-defined sites that theory can model

## Limitations

- Metal loading is limited before atoms cluster
- Long-term stability in fuel cells is still debated

## Uses

- Fuel-cell cathodes (ORR)
- CO₂ reduction
- Hydrogen evolution

## References

1. Yin, Yao, Wu, Zheng, Lin, Liu, Ju, Zhu, Hong, Deng, Zhou, Wei & Li, “Single Cobalt Atoms with Precise N-Coordination as Superior Oxygen Reduction Reaction Catalysts”, Angew. Chem. Int. Ed. 2016. https://doi.org/10.1002/anie.201604802 (primary)
2. Qiao, Wang, Yang, Allard, Jiang, Cui, Liu, Li & Zhang, “Single-atom catalysis of CO oxidation using Pt1/FeOx”, Nat. Chem. 2011. https://doi.org/10.1038/nchem.1095 (primary)
3. Chen, Ji, Wang, Dong, Chen, Li, Shen, Zheng, Zhuang, Wang & Li, “Isolated Single Iron Atoms Anchored on N-Doped Porous Carbon as an Efficient Electrocatalyst for the Oxygen Reduction Reaction”, Angew. Chem. Int. Ed. 2017. https://doi.org/10.1002/anie.201702473 (further reading)
4. Lefèvre, Proietti, Jaouen & Dodelet, “Iron-Based Catalysts with Improved Oxygen Reduction Activity in Polymer Electrolyte Fuel Cells”, Science 2009. https://doi.org/10.1126/science.1170051 (further reading)

Credit: After Yin et al., Angew. Chem. Int. Ed. 2016 (doi:10.1002/anie.201604802) and Qiao et al., Nat. Chem. 2011 (doi:10.1038/nchem.1095). Co–N₄ built in a graphene divacancy; dispersion computed; ORR curves computed with the paper’s E½, shapes illustrative.

## Questions

**What does the “Single-atom catalysts: one metal atom, four nitrogens” template show?** A single-atom catalyst spreads its metal as isolated atoms, each held by nitrogen in a carbon sheet, so every metal atom can be an active site. Pyrolysing a bimetallic Zn/Co framework does it: the linker turns into N-doped carbon, zinc evaporates above 800 °C, and cobalt stays behind as single atoms that reduce oxygen better than commercial platinum on carbon.

**What are the steps shown in “Single-atom catalysts: one metal atom, four nitrogens”?** 1. Framework: Co mixed into a zinc imidazolate framework: the metals start apart, on the framework nodes. 2. Pyrolysis: Carbonizing the linker reduces Co; above 800 °C the Zn evaporates (Yin et al. 2016). 3. Single atoms: Co stays as isolated atoms held by N in porous carbon, seen by aberration-corrected microscopy and EXAFS. 4. Activity: ORR half-wave potential 0.881 V, more positive than commercial Pt/C (0.811 V) in the same study. 5. Stability: The single atoms resisted sintering at 900 °C (Yin et al. 2016).

**What are the starting materials and the product?** Starting materials: A bimetallic Zn/Co zeolitic imidazolate framework (ZIF). Product: Co single atoms on N-doped porous carbon, over 4 wt% Co (Yin et al. 2016).

**Which papers is “Single-atom catalysts: one metal atom, four nitrogens” based on?** Yin, Yao, Wu, Zheng, Lin, Liu, Ju, Zhu, Hong, Deng, Zhou, Wei & Li, “Single Cobalt Atoms with Precise N-Coordination as Superior Oxygen Reduction Reaction Catalysts”, Angew. Chem. Int. Ed. 2016 (doi:10.1002/anie.201604802); Qiao, Wang, Yang, Allard, Jiang, Cui, Liu, Li & Zhang, “Single-atom catalysis of CO oxidation using Pt1/FeOx”, Nat. Chem. 2011 (doi:10.1038/nchem.1095); Chen, Ji, Wang, Dong, Chen, Li, Shen, Zheng, Zhuang, Wang & Li, “Isolated Single Iron Atoms Anchored on N-Doped Porous Carbon as an Efficient Electrocatalyst for the Oxygen Reduction Reaction”, Angew. Chem. Int. Ed. 2017 (doi:10.1002/anie.201702473); Lefèvre, Proietti, Jaouen & Dodelet, “Iron-Based Catalysts with Improved Oxygen Reduction Activity in Polymer Electrolyte Fuel Cells”, Science 2009 (doi:10.1126/science.1170051).

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