In situ electrical conductivity study of Pt-impregnated VOx/γ-Al2O3 catalysts in propene deep oxidation

Brătan, Veronica; Chesler, Paul; Hornoiu, Cristian; Scurtu, Mariana; Postole, G.; Pietrzyk, Piotr; Gervasini, A.; Auroux, A.; Ionescu, N. I.

doi:10.1007/s10853-020-04779-0

Cited by 7 publications

(3 citation statements)

References 48 publications

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“…On the basis of the similarity of the magnetic parameters, the components can be classified into two groups (VO‐1A/B and VO‐2A/B; see also Table 1 ): VO‐1A (≈15%) with magnetic parameters g || = 1.919, A || = 200.9 G and g ⊥ = 1.981, A ⊥ = 75.6 G, calculated g iso = 1.960 and A iso = 117 G; VO‐1B (≈35%) with magnetic parameters g || = 1.907, A || ≅ 201.2 G and g ⊥ ≅ 1.979, A ⊥ = 71.9 G, calculated g iso = 1.955 and A iso = 115 G; VO‐2A (≈25%) with magnetic parameters g || = 1.950, A || ≅ 170.5 G and g ⊥ ≅ 1.971, A ⊥ = 51.0 G, calculated g iso = 1.964 and A iso = 90.8 G; VO‐2B (≈25%) with magnetic parameters g || = 1.938, A | | ≅ 178.3 G and g ⊥ ≅ 1.972, A ⊥ = 57.3 G, calculated g iso = 1.961 and A iso = 97.6 G. Both centers, VO‐1 and VO‐2, represent well‐known monomeric surface vanadyl VO 2+ species in a distorted octahedral (VO‐1) or tetrahedral (VO‐2) environment, as indicated by the values of g iso and A iso , as well as the sharp lines with well‐resolved HFS. [ 27 , 28 ] The parameters listed in Table 1 suggest that the symmetry of the VO‐1 centers is more distorted. [ 27b,c ]…”

Section: Resultsmentioning

confidence: 99%

Enhancing Photocatalysis: Understanding the Mechanistic Diversity in Photocatalysts Modified with Single‐Atom Catalytic Sites

Kruczała,

Neubert,

Dhaka

et al. 2023

Advanced Science

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Surface modification of heterogeneous photocatalysts with single‐atom catalysts (SACs) is an attractive approach for achieving enhanced photocatalytic performance. However, there is limited knowledge of the mechanism of photocatalytic enhancement in SAC‐modified photocatalysts, which makes the rational design of high‐performance SAC‐based photocatalysts challenging. Herein, a series of photocatalysts for the aerobic degradation of pollutants based on anatase TiO2 modified with various low‐cost, non‐noble SACs (vanadate, Cu, and Fe ions) is reported. The most active SAC‐modified photocatalysts outperform TiO2 modified with the corresponding metal oxide nanoparticles and state‐of‐the‐art benchmark photocatalysts such as platinized TiO2 and commercial P25 powders. A combination of in situ electron paramagnetic resonance spectroscopy and theoretical calculations reveal that the best‐performing photocatalysts modified with Cu(II) and vanadate SACs exhibit significant differences in the mechanism of activity enhancement, particularly with respect to the rate of oxygen reduction. The superior performance of vanadate SAC‐modified TiO2 is found to be related to the shallow character of the SAC‐induced intragap states, which allows for both the effective extraction of photogenerated electrons and fast catalytic turnover in the reduction of dioxygen, which translates directly into diminished recombination. These results provide essential guidelines for developing efficient SAC‐based photocatalysts.

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Section: Resultsmentioning

confidence: 99%

Enhancing Photocatalysis: Understanding the Mechanistic Diversity in Photocatalysts Modified with Single‐Atom Catalytic Sites

Kruczała,

Neubert,

Dhaka

et al. 2023

Advanced Science

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“…An insight into the reducibility of the surface vanadium species was derived from the temperature-programmed reduction measurements ( Figure 4 C) since H 2 -TPR profiles strongly depend on a vanadium oxidation state, the VO x surface loading, and a strength of the interaction of the V-containing species with a support [ 60 , 61 ]. Centi et al reported for V-silicalite that the temperature of the maximum rate of reduction was related to the strength of the V-O-M bond (e.g., M = Si, Ti, Al) more than to the coordination of vanadium [ 42 ].…”

Section: Resultsmentioning

confidence: 99%

Modulation of ODH Propane Selectivity by Zeolite Support Desilication: Vanadium Species Anchored to Al-Rich Shell as Crucial Active Sites

Smoliło-Utrata

Tarach

Samson

et al. 2022

IJMS

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The commercially available zeolite HY and its desilicated analogue were subjected to a classical wet impregnation procedure with NH4VO3 to produce catalysts differentiated in acidic and redox properties. Various spectroscopic techniques (in situ probe molecules adsorption and time-resolved propane transformation FT-IR studies, XAS, 51V MAS NMR, and 2D COS UV-vis) were employed to study speciation, local coordination, and reducibility of the vanadium species introduced into the hierarchical faujasite zeolite. The acid-based redox properties of V centres were linked to catalytic activity in the oxidative dehydrogenation of propane. The modification of zeolite via caustic treatment is an effective method of adjusting its basicity—a parameter that plays an important role in the ODH process. The developed mesopore surface ensured the attachment of vanadium species to silanol groups and formation of isolated (SiO)2(HO)V=O and (SiO)3V=O sites or polymeric, highly dispersed forms located in the zeolite micropores. The higher basicity of HYdeSi, due to the presence of the Al-rich shell, aided the activation of the C−H bond leading to a higher selectivity to propene. Its polymerisation and coke formation were inhibited by the lower acid strength of the protonic sites in desilicated zeolite. The Al-rich shell was also beneficial for anchoring V species and thus their reducibility. The operando UV-vis experiments revealed higher reactivity of the bridging oxygens V-O-V over the oxo-group V=O. The (SiO)3V=O species were found to be ineffective in propane oxidation when temperature does not exceed 400 °C.

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“…In the sensor cell, a chemical reaction takes place on the surface of the sensor, which leads to a change in its electrical resistance, a variation recorded by the Hioki 3522-50 RLC bridge connected to the sensing cell. This bridge uses a “custom-made” acquisition software [ 13 , 14 , 15 ], based on the Labview platform, developed by our group. Thus, the analog signal taken from the chemiresistor was converted into a digital signal using a GPIB interface connected to the output of the RLC bridge.…”

Section: Methodsmentioning

confidence: 99%

Cobalt- and Copper-Based Chemiresistors for Low Concentration Methane Detection, a Comparison Study

Chesler

Hornoiu

Anastasescu

et al. 2022

Gels

Self Cite

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Methane is a colorless/odorless major greenhouse effect gas, which can explode when it accumulates at concentrations above 50,000 ppm. Its detection cannot be performed without specialized equipment, namely sensing devices. A series of MOX sensors (chemiresistors type), with CoO and CuO sensitive films were obtained using an eco-friendly and low-cost deposition technique (sol–gel). The sensing films were characterized using AFM and SEM as thin film. The transducers are based on an alumina wafer, with Au or Pt interdigital electrodes (IDE) printed onto the alumina surface. The sensor response was recorded upon sensor exposure to different methane concentrations (target gas) under lab conditions (dried target and carrier gas from gas cylinders), in a constant gas flow, with target gas concentrations in the 5–2000 ppm domain and a direct current (DC) applied to the IDE as sensor operating voltage. Humidity and cross-sensitivity (CO2) measurements were performed, along with sensor stability measurements, to better characterize the obtained sensors. The obtained results emphasize good 3-S sensor parameters (sensitivity, partial selectivity and stability) and also short response time and complete sensor recovery, completed by a low working temperature (220 °C), which are key factors for further development of a new commercial chemiresistor for methane detection.

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In situ electrical conductivity study of Pt-impregnated VOx/γ-Al2O3 catalysts in propene deep oxidation

Cited by 7 publications

References 48 publications

Enhancing Photocatalysis: Understanding the Mechanistic Diversity in Photocatalysts Modified with Single‐Atom Catalytic Sites

Enhancing Photocatalysis: Understanding the Mechanistic Diversity in Photocatalysts Modified with Single‐Atom Catalytic Sites

Modulation of ODH Propane Selectivity by Zeolite Support Desilication: Vanadium Species Anchored to Al-Rich Shell as Crucial Active Sites

Cobalt- and Copper-Based Chemiresistors for Low Concentration Methane Detection, a Comparison Study

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