Revealing the Dynamics of Oxygen Vacancy in ZnO<sub>1–<i>x</i></sub>/Cu during Robust Methanol Synthesis from CO<sub>2</sub>
Fanxing Zhang, Boyang Li, Quan Xu, Ke Wang, XU Jia-ye, Tiantian Wu, Zhenglong Li, Mi Yan, Shoujie Liu, Yi He, Yao Shi, Yaqiong Su, Pengfei Xie
Abstract
The extensive investigation regarding the active site of the Cu/ZnO/Al 2 O 3 catalyst gradually recognizes the paramount importance of the oxygen vacancy in the hydrogenation of CO 2 to methanol. However, it is challenging to probe the nature of oxygen vacancy during methanol synthesis and understand its role in the enhancement of reactivity at the molecule level. Here, the inversed ZnO 1– x /Cu catalysts with abundant oxygen vacancies are prepared by simple ball milling. The interfacial transformations between ZnO 1– x and Cu during material preparation and reaction are elucidated by the correlations of geometrical and chemical states with mechanical energies. The dynamics of the oxygen vacancy during the reaction are revealed as well. The ZnO 1– x /Cu with more oxygen vacancy exhibits a superior CH 3 OH productivity of 1.2 g MeOH g –1 h –1 at 240 °C and a selectivity above 90%. The mechanistic studies reveal that oxygen vacancy promotes the activation of CO 2 to formate and significantly reduces the barrier of the hydrogenation from *HCOO to *H 2 COO intermediates.