Synthesis, optical, and photocatalytic properties of cobalt mixed-metal spinel oxides Co(Al1−xGax)2O4

Lee, Kyureon; Ruddy, Daniel A.; Duković, Gordana; Neale, Nathan R.

doi:10.1039/c4ta06690a

Cited by 18 publications

(14 citation statements)

References 38 publications

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“…Interestingly, comparable spectra with a characteristic band triplet were also obtained from the samples 1.79 Co-SiAl and 0.8 Co-AlSBA, which have no zeolite structures. This suggests, in agreement with conclusion made by the Busca group, [11,26] that the assignment of the observed band triplet to three different types of sites (α, β, γ) located in the internal cavities of pentasil-containing zeolites [17][18][19] might not be correct, particularly since such a characteristic band triplet is not restricted to zeolite materials and was also described, e.g., for cobalt-based blue pigments, [28] cobalt spinels, [29,30] cobalt oxide-apatite materials, [31] Co/Al 2 O 3 , [32], and Co-doped ZnO [33].…”

Section: Uv-vis Drs Studiessupporting

confidence: 78%

Determining the Location of Co2+ in Zeolites by UV-Vis Diffuse Reflection Spectroscopy: A Critical View

et al. 2020

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UV–Vis spectroscopy as well as in situ FTIR spectroscopy of pyridine and CO adsorption were applied to determine the nature of Co species in microporous, mesoporous, and mixed oxide materials like Co–ZSM-5, Co/Na–ZSM-5, Co/Al–SBA-15, and Co/Al2O3–SiO2. Because all sample types show comparable UV–Vis spectra with a characteristic band triplet, the former described UV–Vis band deconvolution method for determination and quantification of individual cationic sites in the zeolite appears doubtful. This is also confirmed by results of pyridine and CO adsorption revealing that all Co–zeolite samples contain two types of Co2+ species located at exchange positions as well as in oxide-like clusters independent of the Co content, while in Co/Al–SBA-15 and Co/Al2O3–SiO2 only Co2+ species in oxide-like clusters occur. Consequently, the measured UV–Vis spectra represent not exclusively isolated Co2+ species, and the characteristic triplet band is not only related to γ-, β-, and α-type Co2+ sites in the zeolite but also to those dispersed on the surface of different oxide supports. The study demonstrates that for proper characterization of the formed Co species, the use of complementary methods is required.

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Section: Uv-vis Drs Studiessupporting

confidence: 78%

Determining the Location of Co2+ in Zeolites by UV-Vis Diffuse Reflection Spectroscopy: A Critical View

et al. 2020

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“…3c, as-prepared CoAl-MMO exhibit XRD patterns consistent with an amorphous structure, which is significantly different from the high crystallinity of ZnAl-MMO. The annealing experiments of CoAl-LDH from 100 to 700°C shows that conversion from rhombohedral to amorphous structure, in which a weak peak at 37.0°is observed and attributed to the (3 1 1) refection of CoAl 2 O 4 [24].…”

Section: Support and Catalyst Characterizationmentioning

confidence: 92%

Platinum nanocrystals supported on CoAl mixed metal oxide nanosheets derived from layered double hydroxides as catalysts for selective hydrogenation of cinnamaldehyde

Tian

Hou

et al. 2015

Journal of Catalysis

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“…Hence, band gap energy ( E g ) of the semiconductor materials need to be improvised or modified to absorb visible light for photocatalytic applications. − Researchers across the globe are in search of alternative techniques to modify the E g of semiconductor metal oxide nanoparticles. These modifications could be carried out by doping of metals, − nonmetals, , and rare-earth materials − and preparation of mixed metal oxides, , graphene-based materials, and core–shell nanocomposites. − Although TiO 2 -based materials have been widely employed for photocatalysis, certain weaknesses, such as stability, cost, and quantum efficiency, have led to ZnO emerging as a suitable alternative …”

Section: Introductionmentioning

confidence: 99%

Rare-Earth-Based MIS Type Core–Shell Nanospheres with Visible-Light-Driven Photocatalytic Activity through an Electron Hopping–Trapping Mechanism

Sivasamy

2018

ACS Omega

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A bilayered rare-earth-based metal–insulator–semiconductor, Dy 2 O 3 @SiO 2 @ZnO core–shell nanospheres, was synthesized by a stepwise synthesis for enhanced visible photocatalytic activity. The prepared material was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, ultraviolet–visible diffuse reflectance spectroscopy, field-emission scanning electron microscopy, energy-dispersive spectroscopy, high-resolution transmission electron microscopy, selected area electron diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, and electron paramagnetic resonance techniques. Dy 2 O 3 @SiO 2 @ZnO core–shell nanospheres were found be in a spherically arranged cauliflower-like morphology (40–60 nm). The high-resolution transmission electron microscopy analysis proved the core–shell morphology of the prepared material with a single Dy 2 O 3 core and two shells comprising SiO 2 and ZnO. The material possessed a surface roughness of 4. 98 nm (2 × 2 μm area) and a band gap energy of 2.82 eV. The in situ generation of OH radicals was confirmed by electron paramagnetic resonance. Electron hopping through the SiO 2 layer from ZnO to Dy 2 O 3 played a major role in trapping electrons in the f-shells of lanthanides, thus, preventing the recombination of electron–hole pair. X-ray photoelectron spectroscopy studies proved the band alignment of the material. Brunauer–Emmett–Teller analysis further showed the core–shell surface area was 14 m 2 /g. The visible photocatalytic activity was tested against 2,4-D (2,4-dichlorophenoxyacetic acid), an endocrine disruptor. The kinetic studies showed that the photocatalytic degradation process followed a pseudo-first-order pathway. The photocatalyst was found to be reusable even up to the third cycle.

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Synthesis, optical, and photocatalytic properties of cobalt mixed-metal spinel oxides Co(Al_1−xGa_x)₂O₄

Abstract: Co(Al1−xGax)2O4 spinels synthesized from molecular precursors exhibit low energy (<2.5 eV) ligand–field transitions that contribute between 46 and 72% of the photocatalytic activity.

Cited by 18 publications

References 38 publications

Determining the Location of Co2+ in Zeolites by UV-Vis Diffuse Reflection Spectroscopy: A Critical View

Determining the Location of Co2+ in Zeolites by UV-Vis Diffuse Reflection Spectroscopy: A Critical View

Platinum nanocrystals supported on CoAl mixed metal oxide nanosheets derived from layered double hydroxides as catalysts for selective hydrogenation of cinnamaldehyde

Rare-Earth-Based MIS Type Core–Shell Nanospheres with Visible-Light-Driven Photocatalytic Activity through an Electron Hopping–Trapping Mechanism

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