Structure-Dependent Dissociation of Water on Cobalt Oxide

Schwarz, Matthias; Faisal, Fahad; Mohr, Susanne; Hohner, Chantal; Werner, Kristin; Xu, Tian-Bing; Škála, Tomáš; Tsud, Nataliya; Matolín, Vladimı́r; Lykhach, Yaroslava; Libuda, Jörg

doi:10.1021/acs.jpclett.8b01033

Cited by 56 publications

(70 citation statements)

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“…Drastic differences were observed with respect to the stability of the OH groups. In particular, we did not observe dissociation of water on CoO(100), suggesting that the stability of OH groups on this surface is comparably low. In a second study, we investigated the anchoring of benzoic acid on different cobalt oxides .…”

Section: Resultsmentioning

confidence: 97%

Self‐Metalation of Anchored Porphyrins on Atomically Defined Cobalt Oxide Surfaces: In situ Studies by Surface Vibrational Spectroscopy

Wähler

Schuster

Libuda

2020

Chemistry A European J

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Metalation of anchored porphyrinsi se ssential for their functionality at hybrid interfaces.I nt his work, we have studiedt he anchoringa nd metalation of af unctionalized porphyrin derivative, 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin (MCTPP), on an atomically-definedC oO(100) film under ultrahigh vacuum(UHV) conditions.W ef ollow both the anchoring to the oxide surface and the self-metalation by surfaceC o 2 + ions via infrared reflection absorptions pectroscopy (IRAS). At 150 K, MCTPP multilayer films adsorb molecularly on CoO(100)w ithout anchoring to the surface. Upon heatingt o1 95 K, the first layer of porphyrin molecules anchors via formationof ab ridgings urface carboxylate. Above 460 K, the MCTPP multilayer desorbs and only the anchored monolayer resides on the surface up to temperatures of 600 Ka pproximately.T he orientation of anchored MCTPPd epends on the surface coverage. At low coverage, the MCTPP adopts an early flat-lyinggeometry,w hereas an upright standingfilm is formed near the multilayer coverage. Self-metalationo fM CTPP depends critically on the surface temperature, the coverage and on the molecular orientation. At 150 K, metalation is largely suppressed, while the degree of metalation increases with increasing temperature and reaches av alue of around 60 %i nt he first monolayer at 450 K. At lower coverage higherm etalation fractions (85 % and above)a re observed, similar as for increasing temperature.

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Section: Resultsmentioning

confidence: 97%

Self‐Metalation of Anchored Porphyrins on Atomically Defined Cobalt Oxide Surfaces: In situ Studies by Surface Vibrational Spectroscopy

Wähler

Schuster

Libuda

2020

Chemistry A European J

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“…21 They observed a single v(OH) peak located at 3650 cm -1 . 21 22 thin films. 22 They found a single v(OD) peak at 2650 cm -1 .…”

Section: Comparison To Experimental Results Reached Through Vibrationmentioning

confidence: 99%

“…21 22 thin films. 22 They found a single v(OD) peak at 2650 cm -1 . They also observed the surface's hydroxylation behavior changing drastically in the interval of 200 K -500 K under the same pressure.…”

Section: Comparison To Experimental Results Reached Through Vibrationmentioning

confidence: 99%

“…after exposing them first to D2O or CO. 22,23 To summarize, experimental characterization of the Co3O4(111) surface can only provide a limited view of the surface at low pressures. These difficulties highlight the importance of theoretical studies for understanding surface structure, especially outside the limits of experimental characterization.…”

Section: Introductionmentioning

confidence: 99%

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Surface Structure of Co₃O₄ (111) under Reactive Gas-Phase Environments

Yan

Sautet

2019

ACS Catal.

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In this work, we thoroughly examined the structure of the Co3O4(111) surface in oxidative and reductive conditions, i.e. in equilibrium with realistic pressures of O2/H2O and H2/H2O, using density functional theory with self-interaction and dispersion corrections. We found that this surface is, in fact, hydroxylated under most reaction conditions, and that subjecting the surface to H2 increases surface Co 2+ concentration. Large structural distortions facilitate the reduction and stabilization of the Co-rich termination. At 423 K, hydroxylation readily occurs on both the Orich and Co-rich surfaces even at water pressure as low as 10 -15 bar, and non-dissociated water molecules appear on the O-rich surface when water pressure is above ~10 -11 bar. Our approach showed good agreement with hybrid functional calculations and vibrational spectroscopy experiments. Under most catalytic conditions, where water is present as a reactant, product, or impurity, we predict that the Co3O4(111) surface will be hydroxylated. Hydroxyls groups and structural distortions undoubtedly play large roles in shaping the surface's catalytic properties and interaction with supported structures. The results of the study show the necessity of the inclusion of hydroxylation and surface Co concentration in computational studies of Co3O4 and provide surface structures under various conditions to aid in future studies on structure and catalytic reactivity of Co3O4(111) used as a support or as an active phase.

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“…1,[23][24][25][26] However, only a few studies have been performed to understand its interaction with water at the molecular level (see e.g. 12,13,20 ). Comparing the interaction of water with Fe3O4(111) and Co3O4(111), the differences are dramatic.…”

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Water on Oxide Surfaces: A Triaqua Surface Coordination Complex on Co₃O₄(111)

et al. 2019

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The interaction of water with metal oxides controls their activity and stability in heterogeneous catalysis and electrocatalysis. In this work, we combine density functional theory (DFT) calculations and infrared reflection absorption spectroscopy (IRAS) to identify the structural motifs formed upon interaction of water with an atomicallydefined Co3O4(111) surface. Three principal structures are observed: (i) strongly bound isolated OD, (ii) extended hydrogen-bonded OD/D2O structures, and (iii) a third structure which has not been reported to our knowledge. In this structure, surface Co2+ ions bind to three D2O molecules to form an octahedrally coordinated Co2+ with a "half hydration shell". We propose that this hydration structure represents an important intermediate in re¬organization and dissolution on oxide surfaces which expose highly unsaturated surface cations. The interaction of transition metal oxides with water heavily affects the stability and reactivity of these materials. Water can induce surface restructuring, phase transitions, sintering or dissolution, all important for heterogeneous catalysis and electrocatalysis. 1-7 Despite the pivotal importance of oxide/water interactions, it has been a long standing challenge to understand these processes at the atomic level. 2 Recently, sophisticated characterization techniques and theoretical analyses led to major breakthroughs. Researchers could identify structural motifs of molecular and dissociated water on several well-defined oxide surfaces at the atomic level. 2,3,8-20 The interaction of Co3O4 and Fe3O4 surfaces with water is of high importance in water oxidation and water-gas shift catalysis. 3,21 Water also affects the interaction between supported Au atoms and Fe3O4. 22 Water adsorption on Fe 3+ terminated Fe3O4(111) was investigated by Freund, Schauermann, Sauer, Paier, and coworkers. 16,17,19 The authors identified OD/D2O structures arranged as ordered overlayers which are weakly bound and desorb below 300 K. 16,17,19

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Structure-Dependent Dissociation of Water on Cobalt Oxide

Cited by 56 publications

References 46 publications

Self‐Metalation of Anchored Porphyrins on Atomically Defined Cobalt Oxide Surfaces: In situ Studies by Surface Vibrational Spectroscopy

Self‐Metalation of Anchored Porphyrins on Atomically Defined Cobalt Oxide Surfaces: In situ Studies by Surface Vibrational Spectroscopy

Surface Structure of Co₃O₄ (111) under Reactive Gas-Phase Environments

Water on Oxide Surfaces: A Triaqua Surface Coordination Complex on Co₃O₄(111)

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Structure-Dependent Dissociation of Water on Cobalt Oxide

Cited by 56 publications

References 46 publications

Self‐Metalation of Anchored Porphyrins on Atomically Defined Cobalt Oxide Surfaces: In situ Studies by Surface Vibrational Spectroscopy

Self‐Metalation of Anchored Porphyrins on Atomically Defined Cobalt Oxide Surfaces: In situ Studies by Surface Vibrational Spectroscopy

Surface Structure of Co3O4 (111) under Reactive Gas-Phase Environments

Water on Oxide Surfaces: A Triaqua Surface Coordination Complex on Co3O4(111)

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Product

Resources

About

Surface Structure of Co₃O₄ (111) under Reactive Gas-Phase Environments

Water on Oxide Surfaces: A Triaqua Surface Coordination Complex on Co₃O₄(111)