Characterization of tungstophosphoric acid supported on MCM-41 mesoporous silica using n-hexane cracking, benzene adsorption, and X-ray diffraction

Jalil, Pasl A.; Al-Daous, Mohammed A.; Al-Arfaj, Abdulrahman A.; Al-Amer, Adnan M.; Beltramini, Jorge; Barri, Sami A. I.

doi:10.1016/s0926-860x(00)00670-0

Cited by 76 publications

(36 citation statements)

References 16 publications

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“…The band at 890 cm -1 and the weak shoulder band at 982 cm -1 can be attributed to the characteristic Keggin type HPW W-O b -W bridge and the terminal W=O, respectively, [21] the broadened bands at 1080 and 800 cm -1 are the characteristic bands of HPW, which overlap with the bands of mesoporous SBA-15. [22,43] These results confirm the presence of HPW encapsulated into the mesoporous silica framework.…”

Section: Ir Spectramentioning

confidence: 93%

Synthesis, Characterization, and Catalytic Properties of SiPW‐X Mesoporous Silica with Heteropolyacid Encapsulated into Their Framework

et al. 2005

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A series of SiPW-X mesoporous silica with Keggin-type heteropolyacids (HPAs) encapsulated into their framework have been synthesized under strong acidic conditions. During hydrolysis of tetraethyl orthosilicate (TEOS), Na 2 HPO 4 (P source) and Na 2 WO 4 (W Source) are added into the initial sol-gel system to form Keggin type HPAs. The final products have been intensively characterized by various techniques, such as XRD, TEM, N 2 adsorption isotherm analysis, and by IR, UV/Visible, and 31 P Magic Angle Spinning (MAS) NMR spectroscopy. Characterization results suggest that samples with an HPA weight percent of 13.3-20.7 % show very ordered hexagonal mesostructures. In addition, HPAs incorpo-

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Section: Ir Spectramentioning

confidence: 93%

Synthesis, Characterization, and Catalytic Properties of SiPW‐X Mesoporous Silica with Heteropolyacid Encapsulated into Their Framework

et al. 2005

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“…At the same time, their catalytic activities are expected to be improved by this procedure. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Mesoporous materials have attracted much attention because of their wide potential industrial applications as catalysts or catalyst supports and hosts since their discovery in the last decade, and it has been widely reported that mesoporous silica SBA-15 has been extensively used as a support and host because of its large pore size, thick walls, and high hydrothermal stability, which make it an excellent candidate for use as a stable solid support as mentioned above. [29][30][31][32][33][34][35][36][37][38][39][40] In our previous work, we prepared a series of insoluble HPA-containing hybrid catalysts by incorporation of HPAs into mesoporous supports during the formation of a mesostructure through acid-base interactions or covalent bond formation.…”

Section: Introductionmentioning

confidence: 99%

In Situ Synthesis, Characterization of SiPMo‐X, and Different Catalytic Properties of SiPMo‐X and SiPW‐X

et al. 2006

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Keywords:In situ synthesis / Heteropolyacids / Mesoporous materials / Encapsulation / Bulky molecule reactions / Zeolites SBA-15 frameworks with encapsulated Keggin type heteropolyacids (HPAs) were synthesized in situ under strongly acidic conditions (pH Ͻ 0). During the hydrolysis of tetraethyl orthosilicate (TEOS), a P-and a Mo source were added into the initial sol-gel system to form Keggin type HPAs. The texture of the final products was studied by the N 2 adsorptiondesorption isotherms and transmission electron microscopy (TEM), and their structure was systematically characterized by X-ray diffraction (XRD), UV/Vis diffuse reflectance-(DRS), infrared-(IR), and 31 P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Characterization results suggest that the samples show very ordered hexagonal mesostructure, and the HPAs that are incorporated into the framework of meso-silica are insoluble during

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“…30 Thus, the product of the mixed PMo 12 -PW 12 solution still retains the Keggin structure. However; the solution-mixed and dry-mixed patterns are not identical; the dry mixture shows two small features at 2θ = 20…”

Section: Resultsmentioning

confidence: 94%

Designing Polyoxometalate based Layer-by-Layer Thin Films on Carbon Nanomaterials for Pseudocapacitive Electrodes

Genovese

Foong

Lian

2015

J. Electrochem. Soc.

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Multi-walled carbon nanotube (MWCNT) electrodes modified with mixtures of PMo 12 O 40 3- (PMo 12 ) and PW 12 O 40 3− (PW 12 ) Keggin ions are investigated for electrochemical capacitor (EC) applications. We have discovered that when these polyoxometalate (POM) ions are combined in solution, they do not just mix physically, but instead react to form the PMo 12-x W x mixed addenda chemistries. By simply mixing PMo 12 and PW 12 in different ratios, a variety of mixed addenda ions, each with unique electrochemical properties, can be easily synthesized. This control over POM redox behavior afforded by the novel mixed addenda synthesis is used along with layer-by-layer (LbL) deposition to design molecular coatings that demonstrate desired pseudocapacitive characteristics. The best performance was achieved with a coating that superimposed a 3: Increased demand for reliable high power energy storage devices has led to growing interest in the development of novel electrode materials for electrochemical capacitors (ECs).1-3 One of the most promising approaches in EC electrode design involves the fabrication of nanostructured composites in which pseudocapacitive materials are immobilized on electrochemical double layer capacitive (EDLC) carbon substrates. There is synergy in this combination as the pseudocapacitive material allows for large charge storage capacity due to surface redox reactions, while the carbon substrate imparts mechanical stability, improved conductivity, and physical capacitive effects.4-5 These types of composite materials including RuO 2 -CNT, 6 MnO 2 -graphene, 7 V 2 O 5 -CNT, 8 and conductive organic polymer (COP)-CNT 9 have been investigated extensively for pseudocapacitive EC electrodes.Although there are many pseudocapacitive alternatives, polyoxometalates (POMs), nanoscale transition metal-oxygen clusters, have emerged as promising building blocks for nanocomposite electrodes. [10][11][12][13][14] POMs have an unmatched range of physical and chemical properties which arise from their seemingly endless variety of molecular structures and sizes. 15 One of the most common and widely researched classes of POM molecules is the Keggin cluster which has the general formula [MX 12 O 40 n− ] in which the central heteroatom (i.e. P, Si, or Ge) is surrounded by twelve addenda atoms (i.e. Mo or W) and forty oxygen atoms. [16][17] These molecules demonstrate high stability of their redox states and participate in fast reversible multielectron transfer reactions, making them ideally suited for pseudocapacitive applications. They also offer tremendous versatility as their electrochemical behavior can be tuned with small adjustments to the molecular chemistry. 17The electrochemical activity of POMs can be combined with the stability and high surface area of carbon substrates to create robust nanocomposite EC electrodes. These POM-carbon composites can be prepared by a variety of techniques including electrodeposition, 18 chemisorption, 19 and layer-by-layer (LbL) self assembly. [20][21][22] The improved capa...

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Characterization of tungstophosphoric acid supported on MCM-41 mesoporous silica using n-hexane cracking, benzene adsorption, and X-ray diffraction

Cited by 76 publications

References 16 publications

Synthesis, Characterization, and Catalytic Properties of SiPW‐X Mesoporous Silica with Heteropolyacid Encapsulated into Their Framework

Synthesis, Characterization, and Catalytic Properties of SiPW‐X Mesoporous Silica with Heteropolyacid Encapsulated into Their Framework

In Situ Synthesis, Characterization of SiPMo‐X, and Different Catalytic Properties of SiPMo‐X and SiPW‐X

Designing Polyoxometalate based Layer-by-Layer Thin Films on Carbon Nanomaterials for Pseudocapacitive Electrodes

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