Erratum

Poppe, J.; Schaak, A.; Janek, Jürgen; Imbihl, R.

doi:10.1002/bbpc.19981021139

Cited by 15 publications

(24 citation statements)

References 2 publications

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“…showed an electrocatalytic effect in catalytic CO In PEEM experiments one illuminates the sample oxidation but again the quantitative and even qualiwith photons from a D discharge lamp (6 eV 2 tative behavior was different [7]. However, for both emission maximum) [7].…”

Section: Experimental Methodsmentioning

confidence: 99%

“…However, for both emission maximum) [7]. Collecting the emitted types of samples the electrocatalytic rate increase photoelectrons one essentially images the local work was always faradaic within the accuracy of our function with a spatial resolution of 0.1-1 mm and measurements (estimated to 50% of the reaction the temporal resolution of video frames (40 ms).…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Such a pumping which we can attribute to the formation of a spreading should start from the tpb, i.e. from the spillover species [7]. As shown by the PEEM images edges of the Pt film.…”

mentioning

confidence: 99%

“…A similar correlate spatially resolving in situ measurements problem exists also in electrocatalysis because the with integral reaction rates [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Spatially resolved measurements of electrochemically induced spillover on porous and microstructured Pt/YSZ catalysts

Imbihl

2000

Solid State Ionics

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Pt / YSZ electrodes prepared from platinum (Pt) and yttria-stabilized zirconia (YSZ) can be applied in electrocatalytic experiments for the promotion of different heterogeneously catalyzed reactions. The strong increase in catalytic activity of Pt / YSZ assemblies on electrochemical polarisation has recently been attributed to the creation of catalytically active spill-over species under non-equilibrium conditions. Our experiments combine locally resolved surface sensitive techniques (SPEM, PEEM) with electrochemical methods in order to resolve the processes at the Pt / YSZ interface and to clarify the nature of the spillover species.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

“…Such a pumping which we can attribute to the formation of a spreading should start from the tpb, i.e. from the spillover species [7]. As shown by the PEEM images edges of the Pt film.…”

mentioning

confidence: 99%

“…A similar correlate spatially resolving in situ measurements problem exists also in electrocatalysis because the with integral reaction rates [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Spatially resolved measurements of electrochemically induced spillover on porous and microstructured Pt/YSZ catalysts

Imbihl

2000

Solid State Ionics

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“…[1][2][3] Die katalytische Wirksamkeit elektrisch polarisierter poröser Metalle auf Festelektrolytsubstraten wurde bereits in über 100 Reaktionen untersucht, und es wurden bis zu 200fache Steigerungen der Reaktionsgeschwindigkeiten beschrieben. Aus mechanistischer Sicht wird dieser elektrochemische Promotionseffekt einer mobilen atomaren "Spillover"-Spezies zugeschrieben, die durch (partielle) Entladung eines mobilen Ions aus dem Festelektrolyten an der Dreiphasengrenze (triple phase boundary, tpb) Festelektrolyt/Metall/Gas entsteht, über die freie Metalloberfläche diffundiert und deren katalytische Eigenschaften nachhaltig verändert.[3-6] Die Bedeutung der elektrochemisch erzeugten Spillover-Spezies und ihre chemische Zusammensetzung konnten erst in den letzten Jahren mithilfe von oberflächenanalytischen Methoden an zwei Systemen nachgewiesen werden: dem Sauerstoffionen-leitenden System Pt/ YSZ (YSZ = Yttrium-stabilisiertes Zirconiumoxid, ZrO 2 + Y 2 O 3 ) [4,[6][7][8][9] und dem Natriumionen-leitenden System Pt/b''-Al 2 O 3 . [10,11] Wir berichten hier über die erste Abbildung des Spillover-Vorgangs und dessen Beschreibung als Diffusionsprozess.…”

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In‐situ‐Abbildung elektrochemisch erzeugten Spillover‐Sauerstoffs auf Pt/YSZ‐Katalysatoren

et al. 2006

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Nach den bahnbrechenden Arbeiten von Vayenas und Mitarbeitern konnte das Konzept der elektrochemischen Promotion heterogen katalysierter Reaktionen in den vergangenen zwei Jahrzehnten in zahlreichen Beispielen demonstriert werden. [1][2][3] Die katalytische Wirksamkeit elektrisch polarisierter poröser Metalle auf Festelektrolytsubstraten wurde bereits in über 100 Reaktionen untersucht, und es wurden bis zu 200fache Steigerungen der Reaktionsgeschwindigkeiten beschrieben. Aus mechanistischer Sicht wird dieser elektrochemische Promotionseffekt einer mobilen atomaren "Spillover"-Spezies zugeschrieben, die durch (partielle) Entladung eines mobilen Ions aus dem Festelektrolyten an der Dreiphasengrenze (triple phase boundary, tpb) Festelektrolyt/Metall/Gas entsteht, über die freie Metalloberfläche diffundiert und deren katalytische Eigenschaften nachhaltig verändert.[3-6] Die Bedeutung der elektrochemisch erzeugten Spillover-Spezies und ihre chemische Zusammensetzung konnten erst in den letzten Jahren mithilfe von oberflächenanalytischen Methoden an zwei Systemen nachgewiesen werden: dem Sauerstoffionen-leitenden System Pt/ YSZ (YSZ = Yttrium-stabilisiertes Zirconiumoxid, ZrO 2 + Y 2 O 3 ) [4,[6][7][8][9] und dem Natriumionen-leitenden System Pt/b''-Al 2 O 3 . [10,11] Wir berichten hier über die erste Abbildung des Spillover-Vorgangs und dessen Beschreibung als Diffusionsprozess. Wir beobachten die Ausbreitung des Sauerstoffs während des elektrochemischen Pumpens auf einem deckenden und gasdichten Platinfilm auf einem YSZ-Kristall.

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In Situ Imaging of Electrochemically Induced Oxygen Spillover on Pt/YSZ Catalysts

et al. 2006

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Following the pioneering work of Vayenas and co-workers, the feasibility of electrochemical promotion of heterogeneously catalyzed reactions has been demonstrated in the past two decades with porous metal catalysts interfaced to solid electrolytes. [1][2][3] The catalytic activity of electrically polarized porous metal electrodes on solid electrolytes has been investigated in over 100 reaction systems, and up to 200-fold increases in rate have been reported. Mechanistically, the promotion effect has been attributed to a charged mobile species that is (partially) discharged at the triple-phase boundary (tpb) (solid electrolyte/metal/gas) and then diffuses over the metal surface, thereby modifying its catalytic activity. [3][4][5][6] The crucial role of the electrochemically generated spillover species and its chemical identity have been proven in recent years by surface analytical techniques for only two systems: the oxygen-ion-conducting Pt/YSZ system (YSZ = yttria-stabilized zirconia, ZrO 2 + Y 2 O 3 ) [4,[6][7][8][9] and the alkali-ion-conducting Pt/b''-Al 2 O 3 system. [10,11] We report herein the imaging of the spillover process itself. We observe the diffusional spreading of oxygen upon electrochemical pumping on a dense platinum film interfaced with YSZ. The experiments provide a better basis for a detailed mechanistic understanding of the electrochemical promotion of surface reactions.The typical cell arrangement of an electrochemical promotion experiment is shown in Figure 1 a, and the generation of spillover oxygen at the tpb is illustrated. Oxygen ions are transported through the YSZ solid electrolyte during the anodic (positive) polarization of the metal catalyst (working electrode), and the following reaction [Eq. (1)] takes place at the tpb:The atomic oxygen generated at the tpb (O tpb ) spills over the electrode surface forming a layer of chemisorbed oxygen (O ad ). It was demonstrated with planar YSZ/Pt model catalysts studied in an ultrahigh-vacuum (UHV) chamber that the electrochemically generated spillover oxygen is identical to oxygen adsorbed from the gas phase. [8,12] However, instead of the expected diffusion from the tpb, a seemingly uniform increase in the oxygen concentration across the metal surface was observed. This uniform increase in oxygen coverage could be attributed to a high density of pores (grain boundaries) in the metal film, which act as fastdiffusion paths to transport oxygen from the Pt/YSZ interface to the outer metal surface.To obtain a planar model catalyst, a pore-free, 200-to 250-nm thick Pt film was deposited by pulsed laser deposition on the (111) plane of YSZ. Subsequent annealing produced a dense Pt film with (111) surface orientation as shown in Figure 1 b. Two spatially resolving methods were applied to image the spillover process in situ. With photoelectron emission microscopy (PEEM), the photoelectrons ejected during illumination by a D 2 discharge lamp (5.5 eV-6.2 eV) are used to image the local work function (WF) with a spatial resolution of approximately 1 m...

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Erratum

Cited by 15 publications

References 2 publications

Spatially resolved measurements of electrochemically induced spillover on porous and microstructured Pt/YSZ catalysts

Spatially resolved measurements of electrochemically induced spillover on porous and microstructured Pt/YSZ catalysts

In‐situ‐Abbildung elektrochemisch erzeugten Spillover‐Sauerstoffs auf Pt/YSZ‐Katalysatoren

In Situ Imaging of Electrochemically Induced Oxygen Spillover on Pt/YSZ Catalysts

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