Extended Brewer hypo?hyper--interionic bonding theory ? I. Theoretical considerations and examples for its experimental confirmation

Neophytides, Stylianos G.; Zafeiratos, Spyridon; Παπακωνσταντίνου, Γεώργιος; Jakšić, Jelena M.; Paloukis, Fotios; Jakšić, Milan M.

doi:10.1016/j.ijhydene.2004.05.008

Cited by 39 publications

(73 citation statements)

References 54 publications

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“…Thus, the SMSI is much stronger when anatase is used as a hypo d-oxide phase. The unique role of anatase form of titania in improvement of catalytic activity in both heterogeneous chemical catalysis and electrocatalysis has been noticed by other authors [26,27].…”

Section: Modification Of Hypo D-oxide Phasementioning

confidence: 73%

Improvement of performances of complex non-platinum electrode materials for hydrogen evolution

Paunović

Popovski²,

Dimitrov

et al. 2006

Electrochimica Acta

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Structural and electrochemical characteristics of hypo-hyper d-electrocatalytic materials aimed for preparation of electrodes for hydrogen evolution were studied and modified in order to improve their performances. All studied materials were of general composition 10% Ni + 18% TiO 2 + C.All materials were prepared of amorphous or crystalline TiO 2 , crystalline Ni or NiCo (10-20 nm) and Vulcan XC-72, by sol-gel procedure. Both, material's intrinsic catalytic activity and surface area were affected by applied modifications. As a result, the electrocatalytic activity was improved, e.g. transformation of TiO 2 into anatase form lowers the HER overpotential for 60 mV. Introduction of MWCNTs was even more effective, lowering η for 120 mV. Co addition to metallic phase lowers η for utmost 195 mV.Combined modification of TiO 2 and carbon substrate lowers η for 145 mV, while the complete modification of all three catalyst's components was the most effective with 230 mV decrease of overpotential.

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Section: Modification Of Hypo D-oxide Phasementioning

confidence: 73%

Improvement of performances of complex non-platinum electrode materials for hydrogen evolution

Paunović

Popovski²,

Dimitrov

et al. 2006

Electrochimica Acta

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“…The same Brewer- [53] type d-d intermetallic bonding model has been the already anticipated basis for Livage and Guzman [19], Neophytides et al [20,21], and Tauster and Fung [22] promotional strong metalsupport interaction (SMSI) effect, with the far-reaching consequences in heterogeneous catalysis, electrocatalysis. The latter systematically predetermined interactive grafting [55,56] and the homogeneous, even uniform distribution of prevailing hyper-d-metallic catalysts upon hypo-d-oxide supports [1-4, 20, 21]. The same type of hypo-hyper-d-dinteractive bonding between nanostructured metal particles of such composite catalysts and their hypo-d-oxide supports additionally reinforces the entire electrocatalytic activity effect [55,56].…”

Section: Hypo-hyper-d-d-interbonding Nature Of Electrocatalysis For Hmentioning

confidence: 99%

“…The latter systematically predetermined interactive grafting [55,56] and the homogeneous, even uniform distribution of prevailing hyper-d-metallic catalysts upon hypo-d-oxide supports [1-4, 20, 21]. The same type of hypo-hyper-d-dinteractive bonding between nanostructured metal particles of such composite catalysts and their hypo-d-oxide supports additionally reinforces the entire electrocatalytic activity effect [55,56]. The pronounced cathodic and anodic interactive spillover (effusion) contributions within the SMSI have been significant for the present theory and its embodiment in electrocatalysis of hydrogen and oxygen electrode reactions for low-and medium-temperature (L&MT) PEMFC and water electrolysis (WE) [1-4, 20, 21].…”

Section: Hypo-hyper-d-d-interbonding Nature Of Electrocatalysis For Hmentioning

confidence: 99%

“…As a consequence, the d band of transition elements has been confirmed to play a crucial role in the bonding, adsorptive, catalytic, and electrocatalytic properties, and, consequently, any search for advances and synergism should be based on the d-d interelectronic correlations and modifications [52,55,56]. Such a state of theoretical knowledge and experimental evidence leads to the conclusion that every hypo-hyperd-d interelectronic phase diagram behaves as the part of the periodic table between the two initial periods of the interacting ingredients.…”

Section: Hypo-hyper-d-d-interbonding Nature Of Electrocatalysis For Hmentioning

confidence: 99%

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Spillover Phenomena and Its Striking Impacts in Electrocatalysis for Hydrogen and Oxygen Electrode Reactions

Παπακωνσταντίνου

Jakšić

Labou

et al. 2011

Advances in Physical Chemistry

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The core subject of the present paper represents the interrelated spillover (effusion) phenomena both of the primary oxide and the H-adatoms, their theory and practice, causes, appearances and consequences, and evidences of existence, their specific properties, and their alterpolar equilibria and kinetic behavior, structural, and resulting catalytic, and double layer charging features. The aim is to introduce electron conductive and d-d interactive individual and composite (mixed valence) hypo-doxide compounds, of increased altervalent capacity, or their suboxides (Magnéli phases), as the interactive catalytic supports and therefrom provide (i) the strong metal-support interaction (SMSI) catalytic effect and (ii) dynamic spillover interactive transfer of primary oxides (M-OH) and free effusional H-adatoms for further electrode reactions and thereby advance the overall electrocatalytic activity. Since hypo-d-oxides feature the exchange membrane properties, the higher the altervalent capacity, the higher the spillover effect. In fact, altervalent hypo-d-oxides impose spontaneous dissociative adsorption of water molecules and then spontaneously pronounced membrane spillover transferring properties instantaneously resulting with corresponding bronze type (Pt/H x WO 3 ) under cathodic and/or its hydrated state (Pt/W(OH) 6 ), responsible for Pt-OH effusion, under anodic polarization, this way establishing instantaneous reversibly revertible alterpolar bronze features (Pt/H 0.35 WO 3 ⇔ Pt/W(OH) 6 ) and substantially advanced electrocatalytic properties of these composite interactive electrocatalysts. Such nanostructured-type electrocatalysts, even of mixed-valence hypo-d-oxide structures (Pt/H 0.35 WO 3 /TiO 2 /C, Pt/H x NbO 3 /TiO 2 /C), have for the first time been synthesized by the sol-gel methods and shown rather high stability, electron conductivity, and nonexchanged initial pure monobronze spillover and catalytic properties. Such a unique electrocatalytic system, as the striking target issue of the present paper, has been shown to be the superior for substantiation of the revertible cell assembly for spontaneous reversible alterpolar interchanges between PEMFC and WE. The main target of the present thorough review study has been to throw some specific insight light on the overall spillover phenomena and their effects in electrocatalysis of oxygen and hydrogen electrode reactions from diverse angles of view and broad contemporary experimental methods and approaches (XPS, FTIR, DRIFT, XRD, potentiodynamic spectra, UHRTEM).

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“…Nanostructured catalysts require much stronger bonding supports, for both long-term stability and higher activity. In this respect titania has an unique role [14].…”

Section: Introductionmentioning

confidence: 99%

Study of structural and electrochemical characteristics of Co-based hypo–hyper d-electrocatalysts for hydrogen evolution

Paunović¹,

Popovski²,

Dimitrov³

et al. 2007

Electrochimica Acta

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Structural and electrochemical characteristics of hypo-hyper d-electrocatalytic materials aimed for preparation of electrodes for hydrogen evolution were studied. The basic catalytic material was prepared of 10% amorphous Co (grain size <2 nm), 18% amorphous TiO 2 and Vulcan XC-72, by sol-gel procedure. A number of modifications were applied aimed at improving the materials performances: (i) TiO 2 was transformed into anatase by heating at 480 • C for 1 h, (ii) multiwalled carbon nanotubes (MWCNT) were used as a catalyst support instead of Vulcan XC-72 and (iii) Mo was added to Co phase in a quantity of 25 at.% (Mo:Co = 1:3).Both, material's intrinsic catalytic activity and surface area were affected by these modifications. As a result, the electrocatalytic activity for hydrogen evolution was improved, e.g. transformation of TiO 2 into anatase form lowers the HER overpotential (η) for 15 mV at 60 mA cm −2 . Introduction of MWCNTs lowered η for 30 mV, while addition of Mo to metallic phase for 40 mV.The complete modification of all three catalyst's components (10% MoCo 3 + 18% anatase + MWCNTs) was the most effective with 60 mV decrease of overpotential.Characterization was made by XRD, SEM, IR and XPS methods. Surface area was measured by means of cyclic voltammetry.

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Extended Brewer hypo?hyper--interionic bonding theory ? I. Theoretical considerations and examples for its experimental confirmation

Cited by 39 publications

References 54 publications

Improvement of performances of complex non-platinum electrode materials for hydrogen evolution

Improvement of performances of complex non-platinum electrode materials for hydrogen evolution

Spillover Phenomena and Its Striking Impacts in Electrocatalysis for Hydrogen and Oxygen Electrode Reactions

Study of structural and electrochemical characteristics of Co-based hypo–hyper d-electrocatalysts for hydrogen evolution

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