Engineering Oxygen Vacancy Densities on (002)-Faceted ZnO Nanoplates: Tunable Adsorption Selectivity between CO2 and C2H6 for Efficient Ethylene Production

Abstract

CO2-assisted oxidative dehydrogenation of ethane (CO2-ODHE) offers a promising route for the simultaneous valorization of CO2 and light alkanes to produce value-added ethylene. However, the cooperative activation of both C–H and C=O bonds along with severe coking remains a major bottleneck. Herein, we demonstrate that oxygen vacancies (OV) on (002)-faceted ZnO nanoplates tune adsorption selectivity between CO2 and C2H6. The OV densities increase with (002) facet exposure, thereby reversing the adsorption selectivity from CO2-dominant at low densities to C2H6-dominant at high densities. This OV-mediated adsorption behavior ensures balanced activation of both reactants, with CO2 precisely activated at OV sites and ethane C–H bonds selectively cleaved at Zn–O–Zn sites. Consequently, the optimized catalyst delivers an average C2H4 yield of 10.3% over the last 100 min of a 5 h reaction at 600 °C, which is better than that of most reported noble metal-based catalysts, while maintaining stable cycling performance. This work establishes facet-regulated oxygen vacancies as an effective defect strategy for synergistic C–H and C=O bond activation toward rational catalyst design.