Unraveling the Roles of the ZnO Surface Structure and Second Metal Doping in Tuning the Catalytic Performance of Ethane Dehydrogenation

Abstract

The ZnO surface is easily reduced during alkane dehydrogenation owing to the formation of surface hydrogen species, resulting in poor catalytic performance. Aiming at revealing ZnO surface structure evolution, the degree of surface reduction, catalyst stability, and the type of key species contributing to surface reduction in the ethane dehydrogenation (EDH) reaction, this work fully investigated the mechanism of the EDH reaction over ZnO and a series of ZnO-based catalysts by using DFT calculations and kMC simulations. The results show that ZnO surface reduction is mainly caused by the interaction of surface H* species from EDH with surface lattice oxygen to generate H₂O(g), leading to surface oxygen vacancy (O_v) formation over ZnO. As the EDH reaction proceeds, the number of O_v increases, and the active center gradually shifts from the Zn–O site to the Zn–Zn_cus site, decreasing the C₂H₄(g) formation activity and ultimately deactivating the ZnO catalyst. Furthermore, the second metal M is introduced into the ZnO surface to construct M/ZnO catalysts, and the Mn/ZnO catalyst is screened out to present better catalytic performance, which is not easily reduced. This work is of great significance in laying a solid foundation for optimizing the catalytic performance of the EDH reaction over ZnO-based catalysts.