posted on 2020-03-19, 13:04authored byXiaoyu Zhang, Hui Wang, Linlin Meng, Xiaowa Nie, Zhenping Qu
Cubic
cuprous oxide is applied in the selective catalytic oxidation
of ammonia to nitrogen (NH3-SCO) to investigate the effect
of structure evolution on catalytic performance. Different structures
(Cu2O, Cu2O–CuO, and CuO) that formed
progressively during the reconstruction process with time are discovered
by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS),
and other characterization methods. The optimal CuO–Cu2O exhibits the best catalytic performance, which has T100% = 210 °C and above 80% N2 selectivity. Combining the experimental method and the density functional
theory (DFT), the oxygen molecule is adsorbed in the form of a stable
molecular state on Cu2O particles, while the dissociative
adsorption of O2 occurs over the mixed CuO–Cu2O and pure CuO phases. It is found that O2 is more
likely to be dissociated and activated on CuO–Cu2O with Eads = −7.15 eV. There
are three kinds of intermediate species (monodentate, bidentate, and
bridging nitrate) observed. The formation of key bidentate nitrate
species facilitates NH3 conversion and N2 formation,
but the other intermediate species have a negative effect on NH3 oxidation.