Mechanism of CO2 conversion to methanol on a highly representative model Cu/ZnO interface

Jurado A., David A., Higham, Michael D., Poh, Yong Rui, Catlow, C. Richard A. ORCID: https://orcid.org/0000-0002-1341-1541 and Krossing, Ingo 2025. Mechanism of CO2 conversion to methanol on a highly representative model Cu/ZnO interface. Journal of Catalysis 446 , 115997. 10.1016/j.jcat.2025.115997

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Abstract

The mechanism of CO2 hydrogenation to methanol is modelled using plane-wave DFT applied to a representative model Cu8-ZnO catalyst system (CZ), obtained via unbiased Monte Carlo exploration of Cu cluster growth over a reconstructed polar ZnO surface. Enhanced CO2 adsorption and activation is found at the active Cu/ZnO interfacial site – resembling a VO vacancy – compared to sites on other Cu-based systems. Three competing methanol formation mechanisms (the formate, carboxyl and CO hydrogenation pathways) are investigated; the least energy-demanding pathway followed the formate mechanism: CO2* → HCOO* → H2COO* → H2COOH* → H2CO* → H3CO* → H3COH. We report the coexistence of several formate adsorbates, some of which being highly stable spectators that were observed spectroscopically. Only one higher energy interfacial Cu/ZnO formate species is a true intermediate relevant for catalysis, undergoing subsequent hydrogenation to methanol. The methoxy intermediate is also highly stable, in agreement with its spectroscopic observation. The most energy-demanding elementary process is hydrogenation of methoxy to methanol (Ea = 1.20 eV). Furthermore, the calculations indicate the possible role of CO and H2CO* in scavenging surface O* by forming CO2* or H2COO*, thus preventing the poisoning of active sites. Finally, water is expected to form from O* on a pure Cu site only, but not the Cu/ZnO interfacial site relevant for MeOH production. The calculations presented provide valuable new insights that allow a more complete rationalisation of experimental observations. They suggest the key steps to enhance catalysis involves destabilizing the long-lived H3CO* favouriting its hydrogenation and fast desorption or stabilizing competing intermediates such as H2COH*.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Chemistry Research Institutes & Centres > Cardiff Catalysis Institute (CCI)
Publisher:	Elsevier
ISSN:	0021-9517
Funders:	EPSRC
Date of First Compliant Deposit:	2 April 2025
Date of Acceptance:	2 February 2025
Last Modified:	07 Apr 2025 13:30
URI:	https://orca.cardiff.ac.uk/id/eprint/177350

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