Ammonia Abatement via Selective Oxidation over Electron-Deficient Copper Catalysts.

Selective catalytic ammonia-to-dinitrogen oxidation (NH 3 -SCO) is highly promising for the abatement of NH 3 emissions from flue gas purification devices. However, there is still a lack of high-performance and cost-effective NH 3 -SCO catalysts for real applications. Here, highly dispersed, electron-deficient Cu-based catalysts were fabricated using nitrogen-doped carbon nanotubes (NCNT) as support. In NH 3 -SCO catalysis, the Cu/NCNT outperformed Cu supported on N-free CNTs (Cu/OCNT) and on other types of supports ( i.e., activated carbon, Al 2 O 3 , and zeolite) in terms of activity, selectivity to the desired product N 2 , and H 2 O resistance. Besides, Cu/NCNT demonstrated a better structural stability against oxidation and a higher NH 3 storage capacity (in the presence of H 2 O vapor) than Cu/OCNT. Quasi in situ X-ray photoelectron spectroscopy revealed that the surface N species facilitated electron transfer from Cu to the NCNT support, resulting in electron-deficient Cu catalysts with superior redox properties, which are essential for NH 3 -SCO catalysis. By temperature-programmed surface reaction studies and systematic kinetic measurements, we unveiled that the NH 3 -SCO reaction over Cu/NCNT proceeded via the internal selective catalytic reaction ( i -SCR) route; i.e. , NH 3 was oxidized first to NO, which then reacted with NH 3 and O 2 to form N 2 and H 2 O. This study paves a new route for the design of highly active, H 2 O-tolerant, and low-cost Cu catalysts for the abatement of slip NH 3 from stationary emissions via selective oxidation to N 2 .