Methanol Oxidation on a Copper Catalyst Investigated Using in Situ X-ray Photoelectron Spectroscopy

Bluhm, Hendrik; Hävecker, Michael; Knop‐Gericke, Axel; Kleimenov, Evgueni; Schlögl, Robert; Teschner, Detre; Bukhtiyarov, Valerii I.; Ogletree, D. Frank; Salmerón, Miquel

doi:10.1021/jp040080j

Cited by 231 publications

(299 citation statements)

References 52 publications

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“…The XPS showed indeed a valence band shape characteristic of the oxide 15 . The band edge appears at 0.9 eV below the Fermi level, as expected from p-type Cu 2 O, which has a band gap of 2 eV.…”

Section: Methodsmentioning

confidence: 85%

Surface Chemistry of Cu in the Presence of CO₂ and H₂O

et al. 2008

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The chemical nature of copper and copper oxide (Cu 2 O) surfaces in the presence of CO 2 and H 2 O at room temperature was investigated using ambient pressure x-ray photoelectron spectroscopy. The studies reveal that in the presence of 0.1 torr CO 2 several species form on the initially clean Cu, including carbonate CO 3 2 , CO 2 δ-and C 0 , while no modifications occur on an oxidized surface. The addition of 0.1 ML Zn to the Cu results in the complete conversion of CO 2 δ-to carbonate. In a mixture of 0.1 torr H 2 O and 0.1 torr CO 2 , new species are formed, including hydroxyl, formate and methoxy, with H 2 O providing the hydrogen needed for the formation of hydrogenated species.

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Section: Methodsmentioning

confidence: 85%

Surface Chemistry of Cu in the Presence of CO₂ and H₂O

et al. 2008

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“…34 Bluhm and co-workers have found an XPS spectroscopic signature of subsurface oxygen earlier in a copper catalyst for methanol oxidation. 35 In their study, peak assignments are tentative due to the challenging interpretation of data with many components and limited signalto-noise ratio at high photon energies. Our Density Functional Theory (DFT) calculations suggest a relative difference of XPS binding energy between subsurface and surface oxygen of 0.8-1.7 eV (Table S2).…”

Section: Acs Paragon Plus Environmentmentioning

confidence: 99%

Subsurface Oxygen in Oxide-Derived Copper Electrocatalysts for Carbon Dioxide Reduction

Eilert

Cavalca

Roberts

et al. 2016

J. Phys. Chem. Lett.

396

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Copper electrocatalysts derived from an oxide have shown extraordinary electrochemical properties for the carbon dioxide reduction reaction (CO 2 RR). Using in situ Ambient Pressure Xray Photoelectron Spectroscopy (APXPS) and quasi in situ Electron Energy Loss Spectroscopy (EELS) in a Transmission Electron Microscope (TEM), we show that there is a substantial amount of residual oxygen in nanostructured, oxide-derived copper electrocatalysts, but no residual copper oxide. Based on these findings in combination with Density Functional Theory (DFT) simulations, we propose that residual subsurface oxygen changes the electronic structure of the catalyst and creates sites with higher carbon monoxide binding energy. If such sites are stable under the strongly reducing conditions found in CO 2 RR, these findings would explain the high efficiencies of oxide-derived copper in reducing carbon dioxide to multi-carbon compounds such as ethylene.

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“…[18][19] A typical instrument (Figure 1) consists of a highpressure cell/chamber, separated from the electron analyzer-which remains in high vacuum-by a differentially pumped electrostatic lens system and series of apertures. [20][21] Such instruments are found at synchrotrons around the world [22][23][24][25][26][27] and are being increasingly used with lab X-ray sources as well, which will further empower the field in the years to come. AP-XPS probes the surface chemistry of catalysts at elevated pressures, 29 identifying and quantifying adsorbates in equilibrium with the gas.…”

Section: Ambient Pressure X-ray Photoelectron Spectroscopymentioning

confidence: 99%

Insights into Electrochemical Reactions from Ambient Pressure Photoelectron Spectroscopy

et al. 2015

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ConspectusThe understanding of fundamental processes in the bulk and at the interfaces of electrochemical devices is a prerequisite for the development of new technologies with higher efficiency and improved performance. One energy storage scheme of great interest is splitting water to form hydrogen and oxygen gas, and converting back to electrical energy by their subsequent recombination with only water as a by-product. However, kinetic limitations to the rate of oxygen-based electrochemical reactions hamper the efficiency in technologies such as solar fuels, fuel cells, and electrolyzers. For these reactions, the use of metal oxides as electrocatalysts is prevalent due to their stability, low cost, and ability to store oxygen within the lattice. However, due to the inherently convoluted nature of electrochemical and chemical processes in electrochemical systems, it is difficult to isolate and study individual electrochemical processes in a complex system. Therefore in situ characterization tools are required for observing related physical and chemical processes directly at the places where and while they occur, and can help elucidate the mechanisms of charge separation and charge transfer at electrochemical interfaces.X-ray photoelectron spectroscopy (XPS), also known as ESCA (electron spectroscopy for chemical analysis) has been used as a quantitative spectroscopic technique that measures the elemental composition, as well as chemical and electronic state of a material. Building from extensive ex situ characterization of electrochemical systems, initial in situ studies were conducted at (near) UHV conditions (≤10 −6 Torr) to probe solid-state electrochemical systems. However through the integration of differential-pumping stages, XPS can now operate at pressures in the Torr range, comprising a technique called ambient pressure XPS (AP-XPS).In this Account, we briefly review the working principles and current status of AP-XPS. We use several recent in situ studies on model electrochemical components as well as operando studies performed by our groups at the Advanced Light Source (ALS) at Lawrence Berkeley National Lab to illustrate that AP-XPS is both a chemically and electrically specific tool since photoelectrons carry information on both the local chemistry and electrical potentials. The applications of AP-XPS to oxygen electrocatalysis shown in this Account span well defined studies of (1) the oxide/oxygen gas interface, (2) the oxide/water vapor interface, and (3) operando measurements of half and full electrochemical cells. Using 2 specially designed model devices, we can expose and isolate the electrode or interface of interest to the incident X-ray beam and AP-XPS analyzer to relate the electrical potentials to the composition/chemical state of the key components and interfaces. We conclude with an outlook on new developments of AP-XPS endstations, which may provide significant improvement in the observation of dynamics over a wide range of time scale, higher spatial resolution, and improved characteri...

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Methanol Oxidation on a Copper Catalyst Investigated Using in Situ X-ray Photoelectron Spectroscopy

Cited by 231 publications

References 52 publications

Surface Chemistry of Cu in the Presence of CO₂ and H₂O

Surface Chemistry of Cu in the Presence of CO₂ and H₂O

Subsurface Oxygen in Oxide-Derived Copper Electrocatalysts for Carbon Dioxide Reduction

Insights into Electrochemical Reactions from Ambient Pressure Photoelectron Spectroscopy

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Methanol Oxidation on a Copper Catalyst Investigated Using in Situ X-ray Photoelectron Spectroscopy

Cited by 231 publications

References 52 publications

Surface Chemistry of Cu in the Presence of CO2 and H2O

Surface Chemistry of Cu in the Presence of CO2 and H2O

Subsurface Oxygen in Oxide-Derived Copper Electrocatalysts for Carbon Dioxide Reduction

Insights into Electrochemical Reactions from Ambient Pressure Photoelectron Spectroscopy

Contact Info

Product

Resources

About

Surface Chemistry of Cu in the Presence of CO₂ and H₂O

Surface Chemistry of Cu in the Presence of CO₂ and H₂O