2024 AIChE Annual Meeting

(391d) Engineering the Cu-ZnO Interface By Atomic Layer Deposition for CO2 Hydrogenation to Methanol

Authors

Junjie Chen - Presenter, University At Buffalo
Nadine Humphrey, University of Pittsburgh
Rachel Spurlock, Stanford University
Anshuman Goswami, Dr. William F. Schneider
Frank Abild-Pedersen, SLAC National Accelerator Laboratory
Stacey Bent, Stanford University
Thomas Jaramillo, Stanford University
CO2 hydrogenation to methanol using renewable H2 is a promising strategy to mitigate global warming and an efficient way for renewable fuel/chemical production. Cu-ZnO-based catalysts are one of the most promising systems for this reaction, while the nature of the active site remains debatable.1 Recent studies on industrially relevant Cu/ZnO/Al2O3 catalysts show the formation of ZnO overlayers on the surface of Cu nanoparticles during the reaction conditions might contribute to their high performance.2-3 However, limited information about the effect of ZnO thickness and the original structure of the Cu-ZnO interface is available.

In this work, we utilized Cu/ZnO/SiO2 with uniform Cu nanocrystals (~7nm) synthesized by colloidal chemistry and controllable ZnO layers prepared by atomic layer deposition (ALD) as a model system to study the synergistic effect between Cu and ZnO (Fig. 1(a-d)).4 ZnO overlayers promote CO2 conversion as well as methanol selectivity (Fig. 1e). Moreover, Cu/SiO2 fully encapsulated by 22 cycles of ZnO ((Cu/SiO2)@22ZnO) shows higher CO2 conversion and methanol selectivity than Cu deposited on 22 cycles ZnO-modified SiO2 (Cu/(22ZnO_SiO2)). Moreover, by increasing the ZnO overlayer from 1 to 22 cycles, the CO2 hydrogenation activity keeps improving (Fig. 1f). In-situ diffuse reflectance infrared spectroscopy (DRIFTS) results show Cu lowers the temperature for the formate to methoxy conversion, and ZnO enhances the surface concentration of methoxy groups.

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  2. Lunkenbein, T.; Schumann, J.; Behrens, M.; Schlögl, R.; Willinger, M. G., Angew. Chem. 2015, 127, 4627-4631.
  3. Behrens, M.; Studt, F.; Kasatkin, I.; Kühl, S.; Hävecker, M.; Abild-Pedersen, F.; Zander, S.; Girgsdies, F.; Kurr, P.; Kniep, B.-L., Science 2012, 336, 893-897.
  4. Nathan, S. S.; Asundi, A. S.; Singh, J. A.; Hoffman, A. S.; Boubnov, A.; Hong, J.; Bare, S. R.; Bent, S. F., ChemCatChem 2021, 13, 770-781.