Combining Atomic Layer Deposition with Surface Organometallic Chemistry to Enhance Atomic-Scale Interactions and Improve the Activity and Selectivity of Cu-Zn/SiO2 Catalysts for the Hydrogenation of CO2 to Methanol

Hui Zhou; Scott R Docherty; Nat Phongprueksathat; Zixuan Chen; Andrey V Bukhtiyarov; Igor P Prosvirin; Olga V Safonova; Atsushi Urakawa; Christophe Copéret; Christoph R Müller; Alexey Fedorov

doi:10.1021/jacsau.3c00319

Combining Atomic Layer Deposition with Surface Organometallic Chemistry to Enhance Atomic-Scale Interactions and Improve the Activity and Selectivity of Cu-Zn/SiO₂ Catalysts for the Hydrogenation of CO₂ to Methanol

JACS Au. 2023 Aug 23;3(9):2536-2549. doi: 10.1021/jacsau.3c00319. eCollection 2023 Sep 25.

Authors

Affiliations

¹ Department of Mechanical and Process Engineering, ETH Zürich, CH-8092 Zürich, Switzerland.
² Department of Energy and Power Engineering, Tsinghua University, 100084 Beijing, China.
³ Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland.
⁴ Department of Chemical Engineering, Delft University of Technology, 2629 HZ Delft, The Netherlands.
⁵ Synchrotron Radiation Facility SKIF, Boreskov Institute of Catalysis SB RAS, 630559 Kol'tsovo, Russia.
⁶ Boreskov Institute of Catalysis, SB RAS, 630090 Novosibirsk, Russia.
⁷ Paul Scherrer Institute, CH-5232 Villingen, Switzerland.

Abstract

The direct synthesis of methanol via the hydrogenation of CO₂, if performed efficiently and selectively, is potentially a powerful technology for CO₂ mitigation. Here, we develop an active and selective Cu-Zn/SiO₂ catalyst for the hydrogenation of CO₂ by introducing copper and zinc onto dehydroxylated silica via surface organometallic chemistry and atomic layer deposition, respectively. At 230 °C and 25 bar, the optimized catalyst shows an intrinsic methanol formation rate of 4.3 g h^-1 g_Cu^-1 and selectivity to methanol of 83%, with a space-time yield of 0.073 g h^-1 g_cat^-1 at a contact time of 0.06 s g mL^-1. X-ray absorption spectroscopy at the Cu and Zn K-edges and X-ray photoelectron spectroscopy studies reveal that the CuZn alloy displays reactive metal support interactions; that is, it is stable under H₂ atmosphere and unstable under conditions of CO₂ hydrogenation, indicating that the dealloyed structure contains the sites promoting methanol synthesis. While solid-state nuclear magnetic resonance studies identify methoxy species as the main stable surface adsorbate, transient operando diffuse reflectance infrared Fourier transform spectroscopy indicates that μ-HCOO*(ZnO_x) species that form on the Cu-Zn/SiO₂ catalyst are hydrogenated to methanol faster than the μ-HCOO*(Cu) species that are found in the Zn-free Cu/SiO₂ catalyst, supporting the role of Zn in providing a higher activity in the Cu-Zn system.