Hydrogenation of CO₂ on ZnO/Cu(100) and ZnO/Cu(111) Catalysts: Role of Copper Structure and Metal–Oxide Interface in Methanol Synthesis

Abstract

The results of kinetic tests and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) show the important role played by a ZnO-copper interface in the generation of CO and the synthesis of methanol from CO hydrogenation. The deposition of nanoparticles of ZnO on Cu(100) and Cu(111), θ < 0.3 monolayer, produces highly active catalysts. The catalytic activity of these systems increases in the sequence: Cu(111) < Cu(100) < ZnO/Cu(111) < ZnO/Cu(100). The structure of the copper substrate influences the catalytic performance of a ZnO-copper interface. Furthermore, size and metal-oxide interactions affect the chemical and catalytic properties of the oxide making the supported nanoparticles different from bulk ZnO. The formation of a ZnO-copper interface favors the binding and conversion of CO into a formate intermediate that is stable on the catalyst surface up to temperatures above 500 K. Alloys of Zn with Cu(111) and Cu(100) were not stable at the elevated temperatures (500-600 K) used for the CO hydrogenation reaction. Reaction with CO oxidized the zinc, enhancing its stability over the copper substrates.

Recent Developments in the Modelling of Heterogeneous Catalysts for CO2 Conversion to Chemicals

“…Several articles about current experimental research of the CO 2 hydrogenation summarize the development of the most recent catalysts with proposed mechanisms. [5,[18][19][20][21] The majority of the literature is focused on methanol synthesis and mechanism of methanol formation on mainly used and most debated ZnO/Cu catalytic surface [22][23][24][25][26] which makes it more accessible to find information about reaction pathways for methanol production. Information about reaction intermediates and reaction pathways on various catalytic surfaces for preparation of other chemicals is not easily obtainable.…”

Thermal reduction of ceria nanostructures on rhodium(111) and re-oxidation by CO2

“…7 This strong metal support interaction (SMSI) forming the oxide layer not only affects the structure of the metal particle but also generates a synergistic effect that drives the reaction. [8][9][10] Furthermore, ceria structures on copper have been shown to achieve even higher turnover rates than the ZnO/Cu system. 11 These results are a strong motivation for the study of inverse configurations, as they might be of importance also in other catalytic systems in the active state.…”

Carbon‐Modified CuO/ZnO Catalyst with High Oxygen Vacancy for CO2 Hydrogenation to Methanol

“…The chemical state of oxygen species is also shown in Figure c. Ambient‐pressure XPS (AP‐XPS) has confirmed that the energy spectrum of lattice oxygen produced by CuO was less than that produced by ZnO in CuO/ZnO catalysts by comparing the changes of energy spectra in the process of reducing CuO to Cu . Therefore, lattice oxygen can be divided into two parts in the CuO/ZnO catalyst.…”