Atomic Layer Deposition ZnO Over-Coated Cu/SiO2 Catalysts for Methanol Synthesis from CO2 Hydrogenation

Abstract

Cu-ZnO-based catalysts are of importance for CO2 utilization to synthesize methanol. However, the mechanisms of CO2 activation, the split of the C=O double bond, and the formation of C-H and O-H bonds are still debatable. To understand this mechanism and to improve the selectivity of methanol formation, the combination of strong electronic adsorption (SEA) and atomic layer deposition (ALD) was used to form catalysts with Cu nanoparticles surrounded by a non-uniform ZnO layer, uniform atomic layer of ZnO, or multiple layers of ZnO on porous SiO2. N2 adsorption, H2 temperature-programmed reduction (H2-TPR) X-ray diffraction (XRD), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), CO-chemisorption, CO2 temperature-programmed desorption (CO2-TPD), X-ray adsorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) were used to characterize the catalysts. The catalyst activity was correlated to the number of metallic sites. The catalyst of 5 wt% Cu over-coated with a single atomic layer of ZnO exhibited higher methanol selectivity. This catalyst has comparatively more metallic sites (smaller Cu particles with good distribution) and basic site (uniform ZnO layer) formation, and a stronger interaction between them, which provided necessary synergy for the CO2 activation and hydrogenation to form methanol.

Recent Progress on Synthesis, Characterization, and Applications of Metal Halide Perovskites@Metal Oxide

“…[144][145][146][147] The nature of the coatings can be controlled by the precursors, while the thickness of the coatings can be tuned by varying the ALD cycles. [144,148,149] For instance, ALD is an effective strategy for the deposition of MO x , such as TiO 2 , [150] Al 2 O 3 , [4,123,125] SiO 2 , [151] ZnO [152] to stabilize QDs. [123,148,153,154] Typically, previous works have proved that the Al 2 O 3 coating that is deposited on the surface of PbSe through ALD could improve the oxidative and photothermal stability, and impedes the movement of the internal atomic and molecular.…”

Designing Nanoparticles and Nanoalloys for Gas-Phase Catalysis with Controlled Surface Reactivity Using Colloidal Synthesis and Atomic Layer Deposition

“…Gao and co-workers [297] applied metal oxide ALD to elucidate the interactions between Cu and ZnO in methanol synthesis via CO 2 hydrogenation. Both components of the active Cu/ZnO phase were brought together by applying ZnO ALD overlayers to Cu/SiO 2 .…”

Effect of the Synthesis Method on Physicochemical Properties and Performance of Cu/ZnO/Nb2O5 Catalysts for CO2 Hydrogenation to Methanol

“…In these processes, a wide variety of value-added chemicals can be obtained. − In particular, methanol is an interesting product of catalytic CO 2 hydrogenation, owing to its broad range of applications. Previous studies showed that Cu/ZnO-based materials are promising for large-scale methanol production from CO 2 and H 2 . , The properties of these materials can be modulated using promoters , and applying different synthesis methods. , Promoters, such as Fe, Ga, , Mg, Al, and In, can increase the dispersion of Cu, maximizing interface sites and the basicity, raising the CO 2 adsorption, while the synthesis method influences the morphology and structure of the catalysts, − allowing the optimization of the methanol generation.…”