Oxygen Vacancy Control of Catalytic Activity of Cu/ZnO for Higher Alcohols Synthesis via Incorporating Ga
Min Tian, Xing Tian, Enjuan Ma, Jiarong Hao, Zhijun Zuo, Wei Huang
Abstract
Incorporating a small number of promoters into Cu/ZnO catalysts could modify the defect structure of the catalyst, leading to differences in the interaction of active sites and dramatically affecting the catalytic performance. Herein, Cu/ZnO catalysts with different oxygen vacancy contents were successfully synthesized by incorporating Ga via the Complete Liquid Phase method (CLP). The studies suggested that changing the Ga loading could effectively tune the oxygen vacancy content. Increased oxygen vacancies enhanced the electron transfer from ZnO to Cu, strengthening the Cu/ZnO interaction and herewith forming more Cu 0 as well as defect structures of Zn δ+, which favored the formation of CH x O*(CH x *) and carbon chain growth. In situ DRIFT results implied that oxygen vacancy facilitated the activation of CO, in which the formation of HCOO* and CH x O* was involved and CH x * formed through CO dissociation and further hydrogenation or the partial dissociation of CH x O* on the Cu 0 active sites. Ultimately, C 2 + OH was produced by the C–C coupling of CH x * with CH x O*/CO* in the Zn δ+ sites. As a result, Cu/ZnO catalyst doped with 6 mol % Ga realized outstanding catalytic performance with 17.22% CO conversion, and the fraction of ethanol and C 2+ OH up to 60.22% and 71.90%, respectively.