Ru nanoparticles on TiO2 with various anatase-to-rutile ratios tuned by selective chemical dissolution: Effect of support polymorph composition on selective benzene hydrogenation

Zhou, Gongbing; Jiang, Lan; He, Daiping

doi:10.1016/j.apcata.2019.02.021

Cited by 18 publications

(12 citation statements)

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“…A maximum yield of 52% was obtained on the Ru@MTSS-1.6% catalyst, which exceeded that obtained on the Ru/TiO 2 catalyst in the O/W Pickering emulsion system (43%) 15 and the Ru/TiO 2 -1.5%HF catalyst (41%). 23 The BSH courses over the four representative catalysts (Ru@MTSS-P, Ru@MTSS-0, Ru@MTSS-1.6%, and Ru@ MTSS-6.3%) are displayed in Figure S1. The contents of benzene, cyclohexene, and cyclohexane exhibited exponentially decreased, parabolic, and monotonically increased variations, respectively, obeying the characteristic of the consecutive reaction.…”

Section: Methodsmentioning

confidence: 99%

Promoting the Performances of TiO₂ Submicrosphere-Embedded Ru Nanoparticles in Benzene Selective Hydrogenation by Morphology Manipulation

Jiang

Dong

Zhou

et al. 2019

Ind. Eng. Chem. Res.

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We embedded Ru nanoparticles into mesoporous TiO2 submicrospheres (MTSSs) with tunable morphologies for benzene selective hydrogenation (BSH). It was identified that the TiO2 precursor prepared by the sol–gel step bore smooth microsphere morphology, which was transformed into the submicrosphere morphology with a rough surface by the subsequent solvothermal treatment and calcination, accompanied by a sharp increase in pore size but a decrease in acidity. The gradual elevation in the content of ammonia in the solvothermal mixture from 0 to 9.1 vol % further increased the pore size while imposing no evident impact on the acidity. In BSH to cyclohexene, the turnover frequency experienced the same variation as the acidity of the Ru@MTSS catalysts, whereas the initial selectivity toward cyclohexene (S 0) volcanically evolved with the pore size passing through a maximum of 90%, ascribed to the easy diffusion and desorption but suppressed readsorption of cyclohexene in the mesopores with proper size.

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Section: Methodsmentioning

confidence: 99%

Promoting the Performances of TiO₂ Submicrosphere-Embedded Ru Nanoparticles in Benzene Selective Hydrogenation by Morphology Manipulation

Jiang

Dong

Zhou

et al. 2019

Ind. Eng. Chem. Res.

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“…In TZ‐1:0.1, the mean bandgap value recorded was 3.6 ± 0.04 eV. This value lies midway between the bandgap of amorphous TiO 2 (~3.96 eV [ 39 ] ) and ZnO (~3.4 eV [ 39 ] ), depicting the combined effect on the energy gaps of the two phases in TZ‐1:0.1. Selective dissolution of anatase widened the bandgap significantly in TZ‐1:0.2 (Table 3).…”

Section: Resultsmentioning

confidence: 99%

“…[ 20 ] The presence of defects may be another factor that can decrease the bandgap of the photocatalyst. [ 18,38–40 ] Oxygen vacancies may cause defect states within the forbidden gap and form new energy levels, termed as midgap states. [ 18,38–40 ] This phenomenon, termed enhanced sub‐bandgap absorption, [ 36 ] helps create localized defect states near the valence band edge and is characterized by tailing (Urbach tails) of the absorption band edge in Tauc plots.…”

Section: Resultsmentioning

confidence: 99%

“…The enhanced photocatalytic activity in TZ‐1:0.3 may be attributed to a synergy between the various phases that facilitated better sorption and improved reactive species generation, as also hypothesized by Zhou et al (2019). [ 39 ] Moreover, defect states may have contributed to better charge separation and improved photocatalytic efficiency. However, according to other researchers, the ratio of anatase to rutile in the photocatalyst may have also contributed to improved photocatalysis (even in the presence of other phases), although a definite ratio–activity relationship has not been determined.…”

Section: Resultsmentioning

confidence: 99%

“…[18,[38][39][40] Oxygen vacancies may cause defect states within the forbidden gap and form new energy levels, termed as midgap states. [18,[38][39][40] This phenomenon, termed enhanced sub-bandgap absorption, [36] helps create localized defect states near the valence band edge and is characterized by tailing (Urbach tails) of the absorption band edge in Tauc plots. [41] Urbach tails were observed in the Tauc plots of TiO 2 -ZnO nanocomposites and not in TiO 2 nanoparticles ( Figure 4).…”

Section: Bandgap Of the Nanocompositementioning

confidence: 99%

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Selective Removal of Photocatalytically Active Anatase TiO₂ Phase from Mixed‐Phase TiO₂‐ZnO Nanocomposites: Impact on Physicochemical Properties and Photocatalytic Activity

Menon

Tatiparti

Mukherji

2020

Energy & Environ Materials

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Heterogeneous photocatalysis employing semiconductor nanoparticles, especially TiO 2 nanoparticles, has attained considerable research interest in recent years. [1] TiO 2 is known to exist in three polymorphic forms, viz. anatase, rutile, and brookite. [2] Often, anatase TiO 2 is considered to be the most photocatalytically active due to high adsorption affinity for organic molecules even at low concentration [3] and low recombination of charge carriers, owing to inherently present oxygen vacancies. [4] However, the inability to utilize visible light limits the practical application of TiO 2 for photocatalysis. [5] Therefore, in recent years, synthesis and application of photocatalytic heterostructures based on TiO 2 and other semiconductors/noble metals have emerged as a strategy to facilitate visible light activity. [6-9] Nanocomposites made of two of the most versatile semiconductor oxides, viz. TiO 2 and ZnO have drawn considerable attention for photocatalytic processes. [10] TiO 2-ZnO nanocomposites have shown good potential for degradation of a variety of organic pollutants, [11,12] and activity under visible irradiation was feasible due to favorable alignment of energy states of both TiO 2 and ZnO. [12-14] Heterostructures comprising of anatase TiO 2 and other metal oxides, [15] and anatase with other TiO 2 phases, such as rutile, [10] are reported to be active under visible irradiation. Their superior photocatalytic activity was attributed to the presence of anatase or a favorable anatase/rutile ratio. The superior photocatalytic activity of anatase TiO 2 is well established. [16] According to literature reports, anatase exhibits an indirect bandgap in addition to its direct bandgap, which enhances charge carrier lifetime. [17] Anatase TiO 2 , being a quasi-stable polymorph, is susceptible to formation of defects and, hence, midgap defect states. [18] On the other hand, pure rutile phase of TiO 2 is reported to be photocatalytically inferior to anatase phase. [3] Contrary to such theories, recent studies have suggested that phase transformations were controlled by the addition of ZnO, such that, at optimal Ti:Zn molar ratios, a unique mix of various TiO 2 , ZnO, and zinc titanate phases coexisted which helped in tailoring the bandgap. This facilitated visible light activity even when anatase was present in negligible amounts or even absent. [19] Interestingly,

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Ru Species Supported on MOF‐Derived N‐Doped TiO₂/C Hybrids as Efficient Electrocatalytic/Photocatalytic Hydrogen Evolution Reaction Catalysts

Yan

Liu

Feng

et al. 2020

Adv Funct Materials

159

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The development of efficient catalysts is of great importance for hydrogen evolution reaction (HER) of water splitting via electrocatalytic/photocatalytic processes to remediate the current severe environmental and energy problems. By aid of the stabilization effects of uncoordinated groups and inherent pore‐confinement of amine‐functionalized metal–organic frameworks (NH2‐MIL‐125), two forms of Ru species including nanoparticles (NPs) and/or single atoms (SAs) can be firmly embedded in NH2‐MIL‐125 derived N‐doped TiO2/C support (N‐TC), and thus obtain two kinds of samples named Ru‐NPs/SAs@N‐TC and Ru‐SAs@N‐TC, respectively. In the synthetic process, the initial feeding amount of Ru3+ ions not only strongly determines the final size and dispersion states of Ru species but also the morphology and defective structures of N‐TC support. Impressively, Ru‐NPs/SAs@N‐TC exhibit superior catalytic activities to Ru‐SAs@N‐TC for either electrocatalytic or photocatalytic HER. This should be attributed to its larger specific surface area and benefiting from synergistic coupling of Ru NPs and Ru SAs. It is envisioned that the present work can provide a new avenue for development of high‐efficiency and multifunctional hybrid catalysts in sustainable energy conversion.

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Ru nanoparticles on TiO2 with various anatase-to-rutile ratios tuned by selective chemical dissolution: Effect of support polymorph composition on selective benzene hydrogenation

Cited by 18 publications

References 50 publications

Promoting the Performances of TiO₂ Submicrosphere-Embedded Ru Nanoparticles in Benzene Selective Hydrogenation by Morphology Manipulation

Promoting the Performances of TiO₂ Submicrosphere-Embedded Ru Nanoparticles in Benzene Selective Hydrogenation by Morphology Manipulation

Selective Removal of Photocatalytically Active Anatase TiO₂ Phase from Mixed‐Phase TiO₂‐ZnO Nanocomposites: Impact on Physicochemical Properties and Photocatalytic Activity

Ru Species Supported on MOF‐Derived N‐Doped TiO₂/C Hybrids as Efficient Electrocatalytic/Photocatalytic Hydrogen Evolution Reaction Catalysts

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Ru nanoparticles on TiO2 with various anatase-to-rutile ratios tuned by selective chemical dissolution: Effect of support polymorph composition on selective benzene hydrogenation

Cited by 18 publications

References 50 publications

Promoting the Performances of TiO2 Submicrosphere-Embedded Ru Nanoparticles in Benzene Selective Hydrogenation by Morphology Manipulation

Promoting the Performances of TiO2 Submicrosphere-Embedded Ru Nanoparticles in Benzene Selective Hydrogenation by Morphology Manipulation

Selective Removal of Photocatalytically Active Anatase TiO2 Phase from Mixed‐Phase TiO2‐ZnO Nanocomposites: Impact on Physicochemical Properties and Photocatalytic Activity

Ru Species Supported on MOF‐Derived N‐Doped TiO2/C Hybrids as Efficient Electrocatalytic/Photocatalytic Hydrogen Evolution Reaction Catalysts

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Promoting the Performances of TiO₂ Submicrosphere-Embedded Ru Nanoparticles in Benzene Selective Hydrogenation by Morphology Manipulation

Promoting the Performances of TiO₂ Submicrosphere-Embedded Ru Nanoparticles in Benzene Selective Hydrogenation by Morphology Manipulation

Selective Removal of Photocatalytically Active Anatase TiO₂ Phase from Mixed‐Phase TiO₂‐ZnO Nanocomposites: Impact on Physicochemical Properties and Photocatalytic Activity

Ru Species Supported on MOF‐Derived N‐Doped TiO₂/C Hybrids as Efficient Electrocatalytic/Photocatalytic Hydrogen Evolution Reaction Catalysts