Abstract text (incl. figure legends and references)

1. Introduction

The active sites for industrial copper/zinc oxide/alumina (Cu/ZnO/Al2O3) catalyzed CO2 transformation have been the subject of intense debate due to the complicated structure together with varied evolution both in activation process and during reaction conditions. Although numerous efforts have been devoted for decades, the precisive identification of desired surface and interface as well as the establishment of dynamic structure-function relationship under catalytic relevant environment still remain a formidable challenge.

2. Objectives

The purpose of this study was to establish the dynamic structure-performance relationship of Cu/ZnO under reaction conditions.

3. Materials & methods

Cu/ZnO, ACTEM, In-situ Holder, ETEM

4. Results

In the current study, the reduction of Cu nanoparticles (NPs) supported on hexagonal ZnO with well-defined nanorod shape (Cu/ZnO) is thoroughly investigated by using the state-of-the-art in-situ spherical aberration corrected transmission electron microscopy (ACTEM) on atomic-scale, while the dynamic feature in subsequent circumstance of reverse water-gas shift (RWGS) reaction is further explored via a combined microscopic and spectroscopic study at technologically interesting temperature range as well as gas composition. The delicate structural information of successfully synthesized Cu/ZnO catalyst after H2 reduction clearly deciphers a semi-spherical morphology of Cu on nonpolar surface of ZnO, whereas an obvious overgrowth of ZnOx moieties alongside faceted Cu NPs on polar terminations. The observed surface changes on catalyst by environmental TEM (ETEM) through increasing the CO2 content under RWGS conditions are accordant to the distribution of intermediates captured by in-situ drift infrared (IR) spectroscopy, which indicates an altered reaction mechanism from "surface-redox" to "formate-Langmuir-Hinshelwood" pathway on the basis of the feed-dependent coverage. In addition, further characterization at low temperature directly elucidates the deactivation of Cu particles on ZnO (10-10) due to the high coverage of accumulated carbon containing species. However, no such poison effect occurs for metallic Cu immobilized on ZnO (0002) and the dynamic behavior derived as the consequence of strong metal-support interaction (SMSI) is verified to play a vital role in facilitating the formation and decomposition of kinetic more favorable metastable species, possible carboxyl on this unique configuration. Hence, the description of dynamic interplay by integrated in-situ approaches could provide fundamental insights into the understanding of structure dependent Cu-ZnO catalytic synergy, and pave the way for rational design of low-temperature catalyst with high efficiency.

5. Conclusion

In conclusion, we present an integrated in-situ study for fundamentally understanding the structure sensitivity of Cu as well as the promotion mechanism of Cu-ZnO interaction under RGWS reaction conditions. These intuitive and spatially resolved evidences as an important feature elaborates a complex scenario of surface chemical reactions in conjunction with dynamical changes of Cu/ZnO catalyst, which could add a new perspective to the ongoing discussion regarding the structure of active sites associated with steps in Cu surface and the Cu-ZnO interface, mainly including the incorporation of partly reduced Zn atoms into Cu steps for the conversion of CO2 molecule.