Insight into dynamic and steady-state active sites for nitrogen activation to ammonia by cobalt-based catalyst.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32005833.
- Also identified by DOI 10.1038/s41467-020-14287-z and PMC identifier 6994663.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The industrial synthesis of ammonia (NH<sub>3</sub>) using iron-based Haber-Bosch catalyst requires harsh reaction conditions. Developing advanced catalysts that perform well at mild conditions (<400 °C, <2 MPa) for industrial application is a long-term goal. Here we report a Co-N-C catalyst with high NH<sub>3</sub> synthesis rate that simultaneously exhibits dynamic and steady-state active sites. Our studies demonstrate that the atomically dispersed cobalt weakly coordinated with pyridine N reacts with surface H<sub>2</sub> to produce NH<sub>3</sub> via a chemical looping pathway. Pyrrolic N serves as an anchor to stabilize the single cobalt atom in the form of Co<sub>1</sub>-N<sub>3.5</sub> that facilitates N<sub>2</sub> adsorption and step-by-step hydrogenation of N<sub>2</sub> to *HNNH, *NH-NH<sub>3</sub> and *NH<sub>2</sub>-NH<sub>4</sub>. Finally, NH<sub>3</sub> is facilely generated via the breaking of the *NH<sub>2</sub>-NH<sub>4</sub> bond. With the co-existence of dynamic and steady-state single atom active sites, the Co-N-C catalyst circumvents the bottleneck of N<sub>2</sub> dissociation, making the synthesis of NH<sub>3</sub> at mild conditions possible.