Supported binary CuO x -Pt catalysts with high activity and thermal stability for the combustion of NH 3 as a carbon-free energy source.

Recently, NH 3 has been thought to be a renewable and carbon-free energy source. The use of NH 3 fuel, however, is hindered by its high ignition temperature and N 2 O/NO production. To overcome these issues, in this study, the combustion of NH 3 over copper oxide (CuO x ) and platinum (Pt) catalysts supported on aluminium silicates (3Al 2 O 3 ·2SiO 2 ), aluminium oxides (Al 2 O 3 ), and silicon oxides (SiO 2 ) were compared. To achieve high catalytic activity for the combustion of NH 3 and high selectivity for N 2 (or low selectively for N 2 O/NO), conditions for the preparation of impregnated binary catalysts were optimised. With respect to the binary catalysts, sequentially impregnated CuO x /Pt/Al 2 O 3 exhibited relatively higher activity, N 2 selectivity, and thermal stability. From XRD and XAFS analyses, CuO x and Pt in CuO x /Pt/Al 2 O 3 were present as CuAl 2 O 4 and metallic Pt, respectively. Given that the combustion activity was closely associated with the Pt nanoparticle size, which was estimated from the Scherrer equation and the pulsed CO technique, highly dispersed Pt nanoparticles were crucial for the low-temperature light-off of NH 3 . For single and binary catalysts, although NH (imide) deformation modes as a key species for N 2 O production were detected by in situ FTIR spectral analysis, the band intensity of CuO x /Pt/Al 2 O 3 was less than those of CuO x /Al 2 O 3 and Pt/Al 2 O 3 . Therefore, CuO x /Pt/Al 2 O 3 exhibits high selectivity for N 2 in NH 3 combustion.