Autor/a:
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Surin, Ivan; Tang, Zhenchen; Geiger, Julian; Damir, Suyash; Eliasson, Henrik; Agrachev, Mikhail; Krumeich, Frank; Mitchell, Sharon; Kondratenko, Vita A.; Kondratenko, Evgenii V.; Jeschke, Gunnar; Erni, Rolf; López, Núria; Pérez-Ramírez, Javier
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Abstract:
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N2O exhibits unique reactivity in oxidation catalysis, but the high manufacturing costs limit its
prospective uses. Direct oxidation of NH3 to N2O can ameliorate this issue but its implementation is
thwarted by suboptimal catalyst selectivity and stability, and the lack of established
structure-performance relationships. Systematic and controlled material nanostructuring offers an
innovative approach for advancement in catalyst design. Herein we discover low-valent manganese
atoms stabilized on ceria, CeO2, as the first stable catalyst for NH3 oxidation to N2O, exhibiting
two-fold higher productivity than the state-of-the-art. Detailed mechanistic, computational and
kinetic studies reveal CeO2 as the mediator of oxygen supply, while undercoordinated manganese species activate O2 and facilitate N2O evolution via N-N bond formation between nitroxyl, HNO,
intermediates. Synthesis via simple impregnation of a small metal quantity (1 wt.%) predominantly
generates isolated manganese sites, while full atomic dispersion is achieved upon redispersion of
sporadic oxide nanoparticles during reaction, as confirmed by advanced microscopic analysis and
electron paramagnetic resonance spectroscopy. Subsequently, manganese speciation is maintained,
and no deactivation is observed over 70 h on stream. CeO2-supported isolated transition metals
emerge as a novel class of materials for N2O production, encouraging future studies to evaluate their
potential in selective catalytic oxidations at large. |