A recent study led by researchers at the Max Planck Institute for Chemical Energy Conversion, in collaboration with international partners, has shed light on the structural dynamics of carbon-supported single-atom catalysts (SACs) during water oxidation. Using advanced in situ characterization techniques, the team discovered that SACs composed of single iron (Fe), cobalt (Co), nickel (Ni), and binary metals NiFe and CoFe undergo significant structural changes, leading to the formation of clusters during the oxygen evolution reaction (OER). This finding challenges previous assumptions that catalytic reactions occur exclusively at isolated metal sites in SACs and provides crucial insights for the development of more efficient catalysts.

Structural Rearrangement Uncovered During Catalysis

Through a combination of in situ X-ray absorption spectroscopy (XAS), atomic scanning transmission electron microscopy (STEM), and electron paramagnetic resonance (EPR), the researchers were able to monitor the catalysts in real-time under reaction conditions. They observed that single metal atoms reorganize to form amorphous (oxy)hydroxide clusters, with dual metal sites bridged by oxygen atoms (M─O─M or M─O─M’, where M/M’ = Fe, Co, Ni). These newly identified dual metal sites are believed to play a pivotal role in enhancing the OER performance, marking a departure from the conventional view that isolated single atoms are solely responsible for catalytic activity.

Biomass-Inspired Synthesis for Enhanced Performance

To construct these SACs, the team employed a novel, biomass-inspired coordination confinement strategy. Using low-cost graphitic carbon nitride (g-C₃N₄) and tannic acid (TA) as precursors, they successfully synthesized N-doped carbon-based SACs through a straightforward and scalable high-temperature carbonization process. The resulting catalysts, especially those containing dual metal elements like CoFe and NiFe, showed superior OER activity compared to their single-metal counterparts. This innovative synthesis method not only improves catalyst performance but also enhances practical viability for large-scale applications.

Leading the Research Effort

The study was led by Dr. Wenchao Wan, a postdoctoral researcher, and Dr. Saskia Heumann, who leads the “Carbon Synthesis and Application” research group at the Max Planck Institute for Chemical Energy Conversion (MPI CEC), which focuses on advanced carbon-based materials for sustainable energy applications. The work was carried out in close collaboration with the Department of Inorganic Spectroscopy (Dr. Liqun Kang and Prof. Serena DeBeer) at the Max Planck Institute for Chemical Energy Conversion, as well with other members of the institute and researchers from other institutions, who contributed their expertise to the project. Their combined expertise of the multidisciplinary research team was essential in elucidating the dynamic behavior of single-atom catalysts (SACs) during water oxidation, which represents a significant step forward in understanding catalyst performance.

Implications for Future Energy Conversion Technologies

The discovery of these dynamic active sites paves the way for a deeper understanding of SAC behavior during catalytic reactions. By pinpointing the true active sites, this research opens up new avenues for optimizing SAC design, with the potential to significantly improve the efficiency of water splitting technologies. This breakthrough represents a major step towards cleaner, more sustainable energy conversion processes and underscores the importance of real-time structural analysis in catalyst development.

This study, recently published in Angewandte Chemie International Edition as an open access article, not only redefines the understanding of SACs in water oxidation but also provides a blueprint for future advancs in electrocatalysis.

Original Paper:

Wenchao Wan, Liqun Kang, Alexander Schnegg, Olaf Ruediger, Zongkun Chen, Christopher S. Allen, Longxiang Liu, Sonia Chabbra, Serena DeBeer, and Saskia Heumann (2025) Carbon-Supported Single Fe/Co/Ni Atom Catalysts for Water Oxidation: Unveiling the Dynamic Active Sites. Angew. Chem. Int. Ed. 2025, e202424629

https://doi.org/10.1002/anie.202424629

Wenchao Wan, Liqun Kang, Alexander Schnegg, Olaf Ruediger, Zongkun Chen, Christopher S. Allen, Longxiang Liu, Sonia Chabbra, Serena DeBeer, and Saskia Heumann (2025) Einatom-Fe/Co/Ni-Katalysatoren auf Kohlenstoffbasis für die Wasseroxidation: Aufklärung der dynamischen aktiven Stellen. Angew. Chem. 2025, e202424629