Investigation on Cu<sub>2</sub>O Surface Reconstruction and Catalytic Performance of NH<sub>3</sub>-SCO by Experimental and DFT Studies
Xiaoyu Zhang, Hui Wang, Linlin Meng, Xiaowa Nie, Zhenping Qu
Abstract
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.