Nanometric Platinum Overlayer to Catalyze NH3 Oxidation with High Turnover Frequency
2020
A pulsed
cathodic arc-plasma deposition of a few-nanometer-thick
Pt(111) overlayer on a 50 μm-thick Fe–Cr–Al metal
foil produced a thin-film catalyst; this catalyst exhibited high activity
for low-temperature NH3 oxidation and was superior to that
of a conventional powder catalyst (Pt/Al2O3).
A metal honeycomb that was fabricated using a metal foil catalyst
successfully demonstrated a light-off performance at a practical gas
hourly space velocity of 1.2 × 105 h–1. Despite its nonporosity and small surface area, the Pt overlayer
is a promising alternative to Pt/Al2O3 for more
efficient ammonia-slip catalysts that use less Pt loading; this is
because the turnover frequency for the NH3 oxidation at
200 °C is more than 180-fold greater than that achieved with
Pt/Al2O3 consisting of Pt nanoparticles. Although
the nanometric Pt overlayer structure was thermally unstable at reaction
temperatures of ≥600 °C, inserting a 250 nm-thick Zr buffer
layer between the Pt overlayer and the metal foil substrate significantly
mitigated the thermal deterioration. The undesired byproducts of NH3 oxidation, NO and NO2, can be efficiently converted
to N2 by a selective catalytic reduction over a V2O5–WO3/TiO2 catalyst in a
tandem reactor system.
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