NOx abatement has been an indispensable part of environmental catalysis for decades. Selective catalytic reduction with ammonia using V2O5/TiO2 is an important technology for removing NOx emitted from industrial facilities. However, it has been a huge challenge for the catalyst to operate at low temperatures, because ammonium bisulfate (ABS) forms and causes deactivation by blocking the pores of the catalyst. Here, we report that physically mixed H-Y zeolite effectively protects vanadium active sites by trapping ABS in micropores. The mixed catalysts operate stably at a low temperature of 220 °C, which is below the dew point of ABS. The sulfur resistance of this system is fully maintained during repeated aging/regeneration cycles because the trapped ABS easily decomposes at 350 °C. Further investigations reveal that the pore structure and the amount of framework Al determined the trapping ability of various zeolites.
Cation
segregation, particularly Sr segregation, toward a perovskite surface
has a significant effect on the performance degradation of a solid
oxide cell (solid oxide electrolysis/fuel cell). Among the number
of key reasons generating the instability of perovskite oxide, surface-accumulated
positively charged defects (oxygen vacancy, Vo
··) have been considered as the most crucial drivers in strongly attracting
negatively charged defects (SrA – site
′) toward the surface. Herein, we demonstrate the
effects of a heterointerface on the redistribution of both positively
and negatively charged defects for a reduction of Vo
·· at a perovskite surface. We took Sm0.5Sr0.5CoO3−δ (SSC) as a model perovskite
film and coated Gd0.1Ce0.9O2−δ (GDC) additionally onto the SSC film to create a heterointerface
(GDC/SSC), resulting in an ∼11-fold reduction in a degradation
rate of ∼8% at 650 °C and ∼10-fold higher surface
exchange (k
q) than a bare SSC film after
150 h at 650 °C. Using X-ray photoelectron spectroscopy and electron
energy loss spectroscopy, we revealed a decrease in positively charged
defects of Vo
·· and transferred electrons
in an SSC film at the GDC/SSC heterointerface, resulting in a suppression
of negatively charged Sr (SrSm
′) segregation.
Finally, the energetic behavior, including the charge transfer phenomenon,
O p-band center, and oxygen vacancy formation energy calculated using
the density functional theory, verified the effects of the heterointerface
on the redistribution of the charged defects, resulting in a remarkable
impact on the stability of perovskite oxide at elevated temperatures.
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