A Study on Catalytic Sites Contiguity in Cu-ZnO-Based Catalysts for CO2 Hydrogenation to Methanol

Our group has proposed the concept of Catalytic Sites Contiguity (CSC) to describe how arrangements and proximity of catalytic sites affect the catalytic performance for carbon dioxide (CO2) conversion reactions. This work continues to investigate the CSC-performance relationship of CO2 hydrogenation to methanol (MeOH) in various Cu–ZnO systems. Three phases are formulated as follows. Phase 1 studied the CSC of atomically-dispersed ZnO-Cu/SiO2 catalysts for improving MeOH formation. Using the atomic layer deposition (ALD), atomically dispersed ZnO (ADZn2+) sites were engineered on uncalcined and calcined Cu/SiO2 samples. Characterizations revealed that Cu+–Cu0 and ADZn2+–Cu0/+ sites contiguities were responsible for CO and MeOH production, respectively. In ALD ZnO-Cu/SiO2-C (ZnO deposited on the calcined Cu/SiO2), an optimal Cu–ZnO sites contiguity featuring isolated hydrogen (H2) activation sites enclosed by abundant CO2 adsorption sites, facilitated the MeOH space-time yield (STY) to 33 g·kgcatal-1·h-1 at 240 oC, three times the yield of its Cu-only counterpart. Phase 2 investigated the enhancement of Cu–ZnO–basic sites contiguity for CO2 hydrogenation to MeOH, compared to Cu0–Cu+, Cu0/+–ADZn2+, and Cu0/+–basic sites contiguities. The MgAlOx- and SiO2-supported catalysts were prepared by the impregnation of Cu and ZnO ALD. MgAlOx-supported catalysts (Cu/MgAlOx and ZnO-Cu/MgAlOx) exhibited stronger basicity than SiO2-supported counterparts (Cu/SiO2 and ZnO-Cu/SiO2), enhancing CO2 adsorption. Results of catalytic evaluation and characterization revealed that Cu0/+–partially reduced ZnO (ZnO1-x)–basic sites contiguity greatly increased CO2 conversion, MeOH selectivity, and turnover frequency of MeOH formation, achieving 64 g·kgCatal-1·h-1 MeOH STY for ZnO-Cu/MgAlOx. In phase 3, the atomic-level contiguity of Cu and ZnO sites was identified, and its impact on the catalytic performance was studied using ZnO/Cu model catalysts prepared by depositing ZnO via ALD (exposure times: 5, 60, and 720 s) onto Cu(OH)2 nanofibers. In situ X-ray absorption spectroscopy combined with density functional theory-assisted spectral simulations allowed identifying various active ZnO species on the Cu surface. Mechanism study indicated that the oxygen-defect ZnO single layers and ZnO nanoparticles on Cu favored MeOH synthesis. The extended ALD exposure time led to an increase in the number of MeOH-forming sites contiguity but did not change selectivity significantly.

Name thesis:degree_name

Doctor of Philosophy (Ph.D.)

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Chemical Engineering

Grantor

University of Saskatchewan

Year dc:date.issued

2026

Author dc:creator

• Chen, Jingye

Advisors dc:contributor.advisor

• Shakouri, Mohsen
• Wang, Hui

Committee members dc:contributor.committeemember

• Dalai, Ajay K.
• Zhang, Lifeng
• Scott, Rob
• Acharya, Bishnu
• Wilson, Lee
• De Klerk, Arno

• Catalytic sites contiguity
• Cu-ZnO catalysts
• CO2 hydrogenation
• Methanol

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10388/17911

OAI identifier oai:identifier

oai:harvest.usask.ca:10388/17911