Kernekoncepter
Plasmonic bimetallic AuRu alloy catalysts can facilitate ammonia synthesis at room temperature and pressure by expediting the hydrogenation of adsorbed nitrogen species via plasmon-mediated hot electrons.
Resumé
The authors report the use of gold-ruthenium (AuRu) plasmonic bimetallic alloys for ammonia synthesis at room temperature and pressure, driven solely by visible light illumination. They synthesize AuRu alloys with different molar ratios (AuRu0.1, AuRu0.2, AuRu0.3) and disperse them on MgO supports for gas-phase ammonia synthesis.
The key findings are:
The AuRu0.2 sample exhibits the highest reactivity and quantum efficiency (~ 60 μmol/g/h and ~0.12% under 100 mW/cm2 visible light), optimizing both optical absorption and catalytic site density.
The light-driven reactions achieve higher reactivity than the thermal-driven reactions at lower temperatures, suggesting non-thermal, plasmon-mediated hot carrier effects.
In-situ DRIFTS measurements show the kinetics of hydrogenation of nitrogen adsorbates is accelerated under light illumination compared to thermocatalysis. The NH3* adsorbate densities increase linearly with illumination power, whereas heating alone results in a non-monotonic change.
Quantum mechanical calculations reveal that the hydrogen-assisted splitting of N2 in the excited state is the key mechanism for the reaction activated at ambient conditions. Light alone or H2 alone cannot achieve N2 dissociation, but their combination can accelerate this key bottleneck step.
The authors conclude that plasmons improve the kinetics of ammonia synthesis via hot-electron-controlled hydrogenation and desorption of intermediate nitrogen species, providing guidance for the design of efficient plasmonic catalysts for sustainable ammonia production.
Statistik
"Ammonia synthesis consumes more than half of the annual industrial hydrogen and contributes up to ~3% of global greenhouse gas emissions."
"The AuRu0.2 sample exhibits a ~60 μmol/g/h reactivity and ~0.12% external quantum efficiency under 100 mW/cm2 visible light illumination."
Citater
"Light energy can be converted into chemical energy through LSPR decay via generation of non-equilibrium hot carriers, strong electric field, and the photothermal effect."
"Fully quantum mechanical calculations reveal that the hydrogen-assisted splitting of N2 in the excited state is the key mechanism for the reaction activated at ambient conditions."