Elucidating the mechanism of the reverse water–gas shift reaction over Au/CeO2 catalysts using operando and transient spectroscopies

Ziemba, Marc; Weyel, Jakob; Heß, Christian

doi:10.1016/j.apcatb.2021.120825

Cited by 47 publications

(76 citation statements)

References 52 publications

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“…As reported previously, the commercial ceria sample exhibits polyhedral particles with a specific surface area of 36 m 2 g −1 , and the sample prepared by decomposition of cerium nitrate consists of ceria sheets with a specific surface area of 57 m 2 g −1 [4,31]. Both samples show a CeO 2 (111) surface termination, but the sheets additionally possess stepped CeO 2 (111) sites [4,31].…”

Section: Catalyst Preparation and Characterizationsupporting

confidence: 56%

“…Although both ceria samples show a (111) termination, the sheets exhibit additional steps (see above), which have been shown to have a positive influence on the reduction behavior [31]. Thus the sheets possess more oxygen defects than the polyhedra, which is clearly reflected in the vibrational signature of the CO region.…”

Section: Resultsmentioning

confidence: 94%

“…Both samples show a CeO 2 (111) surface termination, but the sheets additionally possess stepped CeO 2 (111) sites [4,31]. The gold loading was confirmed by ICP-OES, revealing a gold content of 0.31 wt% for the sheets and 0.27 wt% for the polyhedra [31]. Furthermore, our previous study on Au/CeO 2 (111) sheets has revealed a large dispersion of gold due to presence of single atoms and/or smaller clusters as probed by the CO-Au vibrations using DRIFTS [6].…”

Section: Catalyst Preparation and Characterizationmentioning

confidence: 99%

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Elucidating Active CO–Au Species on Au/CeO2(111): A Combined Modulation Excitation DRIFTS and Density Functional Theory Study

2022

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In this work we elucidate the main steps of the CO oxidation mechanism over Au/CeO2(111), clarifying the course of CO adsorption at a broad variety of surface sites as well as of transmutations of one CO species into another. By combining transient spectroscopy with DFT calculations we provide new evidence that the active centers for CO conversion are single gold atoms. To gain insight into the reaction mechanism, we employ Modulation Excitation (ME) DRIFT spectroscopy in combination with the mathematical tool of Phase Sensitive Detection to identify the active species and perform DFT calculations to facilitate the assignments of the observed bands. The transient nature of the ME-DRIFTS method allows us to sort the observed species temporally, providing further mechanistic insight. Our study highlights the potential of combined transient spectroscopy and theoretical calculations (DFT) to clarify the role of adsorbates observed and to elucidate the reaction mechanism of CO oxidation over supported gold and other noble-metal catalysts.

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Section: Catalyst Preparation and Characterizationsupporting

confidence: 56%

Section: Resultsmentioning

confidence: 94%

Section: Catalyst Preparation and Characterizationmentioning

confidence: 99%

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Elucidating Active CO–Au Species on Au/CeO2(111): A Combined Modulation Excitation DRIFTS and Density Functional Theory Study

2022

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“…Polycrystalline ceria sheets were prepared by thermal decomposition of Ce(NO 3 ) 3 ·6H 2 O (Alfa Aesar, 99.5%) at 600 °C as described in our previous studies. , Ceria cubes and rods were prepared by the hydrothermal synthesis of CeCl 3 ·7H 2 O (Alfa Aesar, 99%) and Ce(NO 3 ) 3 ·6H 2 O (Alfa Aesar, 99.5%) in a NaOH solution (98%, Grüssing GmbH) as described in our previous studies. , Ceria polyhedra or octahedra were purchased from Sigma-Aldrich [<25 nm (BET)].…”

Section: Methodsmentioning

confidence: 99%

Approaching C1 Reaction Mechanisms Using Combined Operando and Transient Analysis: A Case Study on Cu/CeO₂ Catalysts during the LT-Water–Gas Shift Reaction

2022

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The elucidation of reaction mechanisms is an essential part of catalysis research, providing approaches to improve catalysts or, ultimately, to design catalysts based on a profound understanding of their mode of operation. In the context of C1 processes, redox and/or associative mechanisms have been proposed in the literature, but their critical assessment has been a major challenge. Here, we highlight the importance of applying a combination of techniques suited to address both the redox properties and intermediate/adsorbate dynamics in a targeted manner. We illustrate our approach by exploring the mechanism of LT-WGS over low-loaded Cu/CeO2 catalysts using different ceria morphologies (sheets, polyhedra, cubes, and rods) to study the influence of the surface termination. While the results from operando Raman and UV–vis spectroscopy are consistent with a redox mechanism, there is no direct correlation of activity with reducibility. Probing the subsurface/bulk oxygen dynamics using operando Raman F2g analysis coupled with H2 18O highlights the importance of transport properties and the availability of oxygen at the surface. Transient IR spectra reveal the presence of different surface carbonates, none of which are directly involved in the reaction but rather act as spectator species, blocking active sites, as supported by the facet-dependent analysis. From transient IR spectroscopy there is no indication of the involvement of copper, suggesting that the catalytic effect of copper is mainly based on electronic effects. The results from the operando and transient analysis unequivocally support a redox mechanism for LT-WGS over Cu/CeO2 catalysts and demonstrate the potential of our combined spectroscopic approach to distinguish between redox and associative mechanisms in oxide-supported metal catalysts.

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“…This again demonstrates the high selectivity of CO for the S Fe-Ni catalyst. The reverse water-gas shift (RWGS) reaction commonly follows a direct dissociation route (CO 2 → *CO 2 → *CO + *O) or a formate route 28 , 43 – 45 . Since the signal of *HCOO − is negligible, the RWGS reaction on the S Fe-Ni catalyst is more likely to follow a dissociation route.…”

Section: Resultsmentioning

confidence: 99%

Grave-to-cradle upcycling of Ni from electroplating wastewater to photothermal CO2 catalysis

Wang

Zhang

et al. 2022

Nat Commun

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Treating hazardous waste Ni from the electroplating industry is mandated world-wide, is exceptionally expensive, and carries a very high CO2 footprint. Rather than regarding Ni as a disposable waste, the chemicals and petrochemicals industries could instead consider it a huge resource. In the work described herein, we present a strategy for upcycling waste Ni from electroplating wastewater into a photothermal catalyst for converting CO2 to CO. Specifically, magnetic nanoparticles encapsulated in amine functionalized porous SiO2, is demonstrated to efficiently scavenge Ni from electroplating wastewater for utilization in photothermal CO2 catalysis. The core-shell catalyst architecture produces CO at a rate of 1.9 mol·gNi−1·h−1 (44.1 mmol·gcat−1·h−1), a selectivity close to 100%, and notable long-term stability. This strategy of upcycling metal waste into functional, catalytic materials offers a multi-pronged approach for clean and renewable energy technologies.

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Elucidating the mechanism of the reverse water–gas shift reaction over Au/CeO2 catalysts using operando and transient spectroscopies

Cited by 47 publications

References 52 publications

Elucidating Active CO–Au Species on Au/CeO2(111): A Combined Modulation Excitation DRIFTS and Density Functional Theory Study

Elucidating Active CO–Au Species on Au/CeO2(111): A Combined Modulation Excitation DRIFTS and Density Functional Theory Study

Approaching C1 Reaction Mechanisms Using Combined Operando and Transient Analysis: A Case Study on Cu/CeO₂ Catalysts during the LT-Water–Gas Shift Reaction

Grave-to-cradle upcycling of Ni from electroplating wastewater to photothermal CO2 catalysis

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Elucidating the mechanism of the reverse water–gas shift reaction over Au/CeO2 catalysts using operando and transient spectroscopies

Cited by 47 publications

References 52 publications

Elucidating Active CO–Au Species on Au/CeO2(111): A Combined Modulation Excitation DRIFTS and Density Functional Theory Study

Elucidating Active CO–Au Species on Au/CeO2(111): A Combined Modulation Excitation DRIFTS and Density Functional Theory Study

Approaching C1 Reaction Mechanisms Using Combined Operando and Transient Analysis: A Case Study on Cu/CeO2 Catalysts during the LT-Water–Gas Shift Reaction

Grave-to-cradle upcycling of Ni from electroplating wastewater to photothermal CO2 catalysis

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Product

Resources

About

Approaching C1 Reaction Mechanisms Using Combined Operando and Transient Analysis: A Case Study on Cu/CeO₂ Catalysts during the LT-Water–Gas Shift Reaction