The active sites of Cu\u2013ZnO catalysts for water gas shift and CO hydrogenation reactions

Zhenhua Zhang,Weixin Huang,Jincan Kang,Rui You,Shun He,Kun Qian,Zhongmiao Gong,Jie Tian,Yi Cui,Ye Wang,Zongyou Yu,Botao Teng,Aiping Jia,Wenhua Zhang,Xuanye Chen

doi:10.1038/s41467-021-24621-8

Abstract

Cu–ZnO–Al2O3 catalysts are used as the industrial catalysts for water gas shift (WGS) and CO hydrogenation to methanol reactions. Herein, via a comprehensive experimental and theoretical calculation study of a series of ZnO/Cu nanocrystals inverse catalysts with well-defined Cu structures, we report that the ZnO–Cu catalysts undergo Cu structure-dependent and reaction-sensitive in situ restructuring during WGS and CO hydrogenation reactions under typical reaction conditions, forming the active sites of CuCu(100)-hydroxylated ZnO ensemble and CuCu(611)Zn alloy, respectively. These results provide insights into the active sites of Cu–ZnO catalysts for the WGS and CO hydrogenation reactions and reveal the Cu structural effects, and offer the feasible guideline for optimizing the structures of Cu–ZnO–Al2O3 catalysts.

Highlights

Cu–ZnO–Al2O3 catalysts are used as the industrial catalysts for water gas shift (WGS) and CO hydrogenation to methanol reactions
Via a combined experimental and theoretical study of various ZnO/Cu–NCs inverse catalysts, we successfully identify the active sites of Cu-ZnO catalysts for WGS and CO hydrogenation reactions respectively as the CuCu(100)hydroxylated ZnO ensemble and CuCu(611)Zn alloy and elucidate the reaction mechanisms, which nicely exemplify the concept of reaction-dependent restructuring and active site of a catalyst
Uniform capping ligands-free Cu2O NCs, including cubic Cu2O NCs (c-Cu2O) enclosed with {100} crystal planes with different size distributions of 682 ± 92, 109 ± 10, and 34 ± 4.5 nm, octahedral Cu2O NCs enclosed with {111} crystal planes with size distribution of 583 ± 74 nm, and rhombic dodecahedral Cu2O NCs enclosed with {110} crystal planes with size distribution of 550 ± 93 nm (Fig. 1a1–e1, Supplementary Figs. 1 and 2), were prepared according to well established procedures[29,30,31,32] and used as the supports to synthesize a series of ZnO/Cu2O-NCs catalysts with preserved morphologies of corresponding Cu2O NCs supports (Fig. 1a2–e2, Supplementary Table 1 and Supplementary Figs. 3–7)

Summary

Introduction

Cu–ZnO–Al2O3 catalysts are used as the industrial catalysts for water gas shift (WGS) and CO hydrogenation to methanol reactions. In the TPSR spectra of CO and H2O in our previous results over Cu NCs32, the H2 production occurs at a higher temperature than the CO2 production, indicating the H2 production as the rate-limiting step in the Cu-catalyzed WGS reaction with the Cu-CuxO interface as the active site.

Results

Conclusion