科研之友
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摘要
Selective catalytic NH3 -to-N2 oxidation (NH3 -SCO) is highly promising for abating NH3 emissions slipped from stationary flue gas after -treatment devices. Its practical application, however, is limited by the non -availability of low-cost catalysts with high activity and N2 selectivity. Here, using defect -rich nitrogen -doped carbon nanotubes (NCNT-AW) as the support, we developed a highly active and durable copper -based NH3 -SCO catalyst with a high abundance of cuprous (Cu+ ) sites. The obtained Cu/NCNT-AW catalyst demonstrated outstanding activity with a T50 (i.e. the temperature to reach 50% NH3 conversion) of 174 degrees C in the NH3 -SCO reaction, which outperformed not only the Cu catalyst supported on N -free O-functionalized CNTs (OCNTs) or NCNT with less surface defects, but also those most active Cu catalysts in open literature. Reaction kinetics measurements and temperature -programmed surface reactions using NH3 as a probe molecule revealed that the NH3 -SCO reaction on Cu/NCNTAW follows an internal selective catalytic reaction (i -SCR) route involving nitric oxide (NO) as a key intermediate. According to mechanistic investigations by X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray absorption spectroscopy, the superior NH3 -SCO performance of Cu/NCNT-AW originated from a synergy of surface defects and N-dopants. Specifically, surface defects promoted the anchoring of CuO nanoparticles on N -containing sites and, thereby, enabled efficient electron transfer from N to CuO, increasing significantly the fraction of SCR -active Cu+ sites in the catalyst. This study puts forward a new idea for manipulating and utilizing the interplay of defects and N-dopants on carbon surfaces to fabricate Cu+ -rich Cu catalysts for efficient abatement of slip NH3 emissions via selective oxidation.
