In Situ Spectroscopic Characterization and Theoretical Calculations Identify Partially Reduced ZnO1−x/Cu Interfaces for Methanol Synthesis from CO2

• Published in: Angewandte Chemie International Edition Vol. 61; no. 23; pp. e202202330 - n/a
• Main Authors: Liu, Xinyu, Luo, Jie, Wang, Hengwei, Huang, Li, Wang, Shasha, Li, Shang, Sun, Zhihu, Sun, Fanfei, Jiang, Zheng, Wei, Shiqiang, Li, Wei‐Xue, Lu, Junling
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 07-06-2022
• Edition: International ed. in English
• Subjects: Absorption spectroscopy; Alloys; Aluminum oxide; Atomic Layer Deposition; Atomic layer epitaxy; Carbon dioxide; Catalysts; Chemical composition; CO2 Hydrogenation; Copper; Copper base alloys; Copper zinc alloys; Density functional theory; Dispersion; First-principles microkinetics; High pressure; In Situ XAFS; Interfaces; Metal-Oxide Interface; Methanol; Nanoparticles; Oxygen; Selectivity; Structural analysis; Zinc oxide
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202202330

The active site of the industrial Cu/ZnO/Al2O3 catalyst used in CO2 hydrogenation to methanol has been debated for decades. Grand challenges remain in the characterization of structure, composition, and chemical state, both microscopically and spectroscopically, and complete theoretical calculations are limited when it comes to describing the intrinsic activity of the catalyst over the diverse range of structures that emerge under realistic conditions. Here a series of inverse model catalysts of ZnO on copper hydroxide were prepared where the size of ZnO was precisely tuned from atomically dispersed species to nanoparticles using atomic layer deposition. ZnO decoration boosted methanol formation to a rate of 877 gMeOH kgcat−1 h−1 with ≈80 % selectivity at 493 K. High pressure in situ X‐ray absorption spectroscopy demonstrated that the atomically dispersed ZnO species are prone to aggregate at oxygen‐deficient ZnO ensembles instead of forming CuZn metal alloys. By modeling various potential active structures, density functional theory calculations and microkinetic simulations revealed that ZnO/Cu interfaces with oxygen vacancies, rather than stoichiometric interfaces, Cu and CuZn alloys were essential to catalytic activation.
High‐pressure in situ X‐ray absorption spectroscopy disclosed the structure evolution of isolated Zn species to oxygen‐deficient ZnO ensembles on an atomically dispersed ZnO/Cu catalyst during methanol synthesis from CO2. Density functional theory calculations further revealed that oxygen vacancies at the interfaces play an important role in the active site.