Thermally stable high-loading single Cu sites on ZSM-5 for selective catalytic oxidation of NH<sub>3</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39042689.
- Also identified by DOI 10.1073/pnas.2404830121 and PMC identifier 11295017.
- Licence recorded as CC BY-NC-ND.
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Abstract
Rigorous comparisons between single site- and nanoparticle (NP)-dispersed catalysts featuring the same composition, in terms of activity, selectivity, and reaction mechanism, are limited. This limitation is partly due to the tendency of single metal atoms to sinter into aggregated NPs at high loadings and elevated temperatures, driven by a decrease in metal surface free energy. Here, we have developed a unique two-step method for the synthesis of single Cu sites on ZSM-5 (termed Cu<sub>S</sub>/ZSM-5) with high thermal stability. The atomic-level dispersion of single Cu sites was confirmed through scanning transmission electron microscopy, X-ray absorption fine structure (XAFS), and electron paramagnetic resonance spectroscopy. The Cu<sub>S</sub>/ZSM-5 catalyst was compared to a CuO NP-based catalyst (termed Cu<sub>N</sub>/ZSM-5) in the oxidation of NH<sub>3</sub> to N<sub>2</sub>, with the former exhibiting superior activity and selectivity. Furthermore, operando XAFS and diffuse reflectance infrared Fourier transform spectroscopy studies were conducted to simultaneously assess the fate of the Cu and the surface adsorbates, providing a comprehensive understanding of the mechanism of the two catalysts. The study shows that the facile redox behavior exhibited by single Cu sites correlates with the enhanced activity observed for the Cu<sub>S</sub>/ZSM-5 catalyst.