New development of concept of electronegativity

Li, Keyan; Xue, Dongfeng

doi:10.1007/s11434-008-0578-9

Cited by 29 publications

(24 citation statements)

References 37 publications

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“…Here, we approximate ionic character by subtracting each metal's Pauling electronegativity 89 from that of oxygen (i.e. χ O -χ M ) and correlate this metric with our calculated initial turnover frequencies.…”

Section: Discussionmentioning

confidence: 99%

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Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H₂O₂

2015

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Supported metal oxides are important catalysts for selective oxidation processes, such as alkene epoxidation with H 2 O 2 . The reactivity of these catalysts is dependent on both identity and oxide structure. The dependence of the latter on synthesis method can confound attempts at comparative studies across the periodic table. Here, SiO 2 -supported metal oxide catalysts of Ti(IV), Zr(IV), Hf(IV), V(V), Nb(V) and Ta(V) (all of Groups IV and V) were synthesized by grafting a series of related calixarene coordination complexes at surface densities less than ~0.25 nm -2 . Select catalysts were investigated by solid state NMR, UV-visible, and Xray absorption near edge spectroscopies. As-synthesized and calcined materials were examined for the epoxidation of cyclohexene and styrene (1.0 M) with H 2 O 2 (0.10 M) at 45°C and 65°C.Nb catalysts emerge as high-performing materials, with calcined Nb-SiO 2 proceeding at a cyclohexene turnover frequency of 2.4 min -1 (>2x faster than Ti-SiO 2 ) and with ~85% selectivity towards direct (non-radical) epoxidation pathways. As-synthesized Zr, Hf and Ta catalysts have improved direct pathway selectivities compared to their calcined versions, particularly evident for Ta-SiO 2 . Finally, when the materials are synthesized from these precursors, but not simple metal chlorides, the direct pathway reaction rate correlates with Pauling electronegativities of the metals, demonstrating clear periodic trends in intrinsic Lewis acid catalytic behavior.

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Section: Discussionmentioning

confidence: 99%

“…Ionic character is estimated by subtracting the Pauling electronegativity of each metal from that of oxygen 89. Error bars represent alternative calculations of TOF from 10 min (high) and 30 min (low) of reaction.…”

mentioning

confidence: 99%

Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H₂O₂

2015

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“…aluminum, iron, or presence of [Si 4 MgO 16 ] pentamer. Another possibility in color differences might be the electronegativity which also may influence on local disordering, the point defects density and their distribution [31][32][33].…”

Section: Uv-vis Spectroscopymentioning

confidence: 99%

“…might also be associated with electronegativity (EN) [31][32][33]. The EN concept assumed that the ion and material properties accurately depends on EN values of elements in different valence states by including the chemical environment of atoms (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Rondorfite-type structure—XPS and UV–vis study

Dulski

Bilewska

Wojtyniak

et al. 2015

Materials Research Bulletin

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Transition Metal Oxide Work Functions: The Influence of Cation Oxidation State and Oxygen Vacancies

Greiner

Chai

Helander

et al. 2012

Adv Funct Materials

740

629

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Transition metal oxides are capable of a wide range of work functions. This quality allows them to be used in many applications that involve charge transfer with adsorbed molecules, for example as heterogeneous catalysts, as charge-injection layers in organic electronics, and as electrodes in fuel cells. Chemical and structural factors can alter transition-metal oxide work functions, often making their work functions diffi cult to control. Little is known about the effects of the cation oxidation state and point defects on the oxide work function. It is necessary to understand how such chemical and structural factors affect work functions in order to controllably tune transition metal oxides for desired applications. Here, a correlation between the oxide work function and cation oxidation state is demonstrated. This correlation is attributed to the change in cation electronegativity with oxidation state. A model is presented that relates the work function to the oxygen defi ciency for d 0 oxides in the limit of dilute oxygen vacancies. It is proposed that the rapid initial decrease in work function, observed for d 0 oxides, is caused by an increase in the density of donor-like defect states. It is also shown that oxides tend to have decreased work functions near a metal/metal-oxide interface as a consequence of the relationship between defects and work function. These insights provide guidelines for tuning transition metal oxide work functions.

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New development of concept of electronegativity

Cited by 29 publications

References 37 publications

Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H₂O₂

Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H₂O₂

Rondorfite-type structure—XPS and UV–vis study

Transition Metal Oxide Work Functions: The Influence of Cation Oxidation State and Oxygen Vacancies

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New development of concept of electronegativity

Cited by 29 publications

References 37 publications

Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H2O2

Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H2O2

Rondorfite-type structure—XPS and UV–vis study

Transition Metal Oxide Work Functions: The Influence of Cation Oxidation State and Oxygen Vacancies

Contact Info

Product

Resources

About

Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H₂O₂

Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H₂O₂