Biochar as supporting material for heterogeneous Mn(II) catalysts: Efficient olefins epoxidation with H2O2

Pierri, Letícia de; Gemenetzi, Aikaterini; Mavrogiorgou, Alexandra; Regitano, Jussara Borges; Deligiannakis, Yiannis; Louloudi, Maria

doi:10.1016/j.mcat.2020.110946

Cited by 16 publications

(8 citation statements)

References 26 publications

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“…Only under the concurrent presence of light and Ag 0 @SiO 2 PNPs, did the value of the catalytic solution potential E h show a drop, as shown in Figure B,C. Interestingly, a comparison of the catalytic data (Figure ) and the E h evolution (Figure ) confirms a direct correlation of the E h evolution with the kinetics of oxidation catalysis, in all of the above systems, as we have previously shown. − ,− Under [light + Ag 0 @SiO 2 ]: [i] the catalytic process of the LMn II system was temporarily paused and [ii] the solution potential, E h , dropped. After switching-off the light, the aforementioned effects were fully reversed.…”

Section: Resultsmentioning

confidence: 54%

Reversible Plasmonic Switch in a Molecular Oxidation Catalysis Process

et al. 2022

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Currently, plasmonic nanoparticles (PNPs) are considered highly efficient enhancers of catalytic processes. Herein, we report a concept where plasmonic Ag0@SiO2 nanoparticles can reversibly switch-off an oxidation catalytic process under light-excitation. The catalytic process recommences when illumination is stopped. The catalytic system under study is a well-characterized molecular LMnII catalyst that performs alkene oxidation, with H2O2 as the oxidant. Three types of plasmonic core–shell Ag0@SiO2 nanoparticles, with a SiO2 shell of varying thickness (0.1–5 nm), were utilized in this study. Using electron paramagnetic resonance spectroscopy, we have identified the reversible inhibition of the transient LMnIVO intermediate formation, to be the key-step of the photoinduced pause of the catalytic process by the Ag0@SiO2 PNPs. Surface-enhanced Raman spectroscopy (SERS) and redox potential data show that the plasmonic Ag0@SiO2 NPs exert a moderate SERS effect on the LMnII catalyst, and a considerable lowering of the solution redox potential E h. Our data show that near-field generation is not the sole origin of inhibition of LMnIVO formation, while plasmonic heating was insignificant. We suggest that the generation of hot electrons by the Ag0@SiO2 PNPs is implicated, along with near-field generation, in the reversible switch-off of the catalytic process.

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Section: Resultsmentioning

confidence: 54%

Reversible Plasmonic Switch in a Molecular Oxidation Catalysis Process

et al. 2022

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“…, from −45 to −134 mV after 60 min of reaction (Figure A). As we have analyzed previously, this is a well-understood phenomenon, − where the E h trend reflects the enrichment of the liquid phase of the reaction with reducing agents such as hydrides that are formed during the catalytic cycle of HCOOH dehydrogenation. − As shown in Figure , the catalytic system’s E h was monitored under illumination with the three LED sources. Notice that the data presented in Figure A show the E h shift, for reaction time intervals of 10 min, under decreasing LED light intensities.…”

Section: Resultsmentioning

confidence: 95%

Controlled Photoplasmonic Enhancement of H₂ Production via Formic Acid Dehydrogenation by a Molecular Fe Catalyst

2023

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Plasmonic nanoparticles (PNPs) constitute a significant category of photoresponsive materials whose exploitation in photoboosted catalysis is a forward-looking strategy. Here, it is demonstrated that photoexcited core−shell Ag 0 @SiO 2 PNPs can dramatically enhance formic acid dehydrogenation (FADH), catalyzed by the molecular catalyst [Fe(BF 4 ) 2 •6H 2 O/ P(CH 2 CH 2 PPh 2 ) 3 , PP 3 ]. In the presence of photoexcited Ag 0 @SiO 2 PNPs, the optimized catalytic system [(Fe/PP 3 )/HCOOH/Ag 0 @SiO 2 /hv] achieves an almost 10-fold increase of the H 2 -gasproduction rate vs [(Fe/PP 3 )/HCOOH] (173 vs 17 mL H 2 min −1 , using 12.5 μmol of catalyst), while the turnover numbers (TONs) are boosted by ∼400% (35,643 vs 9615) and the turnover frequencies (TOFs) by ∼600% (17,821 h −1 vs 2885 h −1 ). Selective excitation at wavelengths (λ ex ) spanning the photoresponse profile of Ag 0 @SiO 2 NPs demonstrates that the FADH enhancement is maximal at λ ex = 405 nm, which is at the peak of the photoplasmonic response of Ag 0 @SiO 2 NPs. Monitoring of the solution potential (E h ) under catalytic conditions reveals that the photoexcitation of Ag 0 @SiO 2 PNPs injects hot electrons, as reducing agents, into the reaction solution. Varying the SiO 2 -shell thickness of Ag 0 @SiO 2 PNPs in the range of 3−5 nm allowed control of the hot-electron injection rates and the ensuing FADH rates. The present results are discussed in the context of the catalytic cycle of the [(Fe/PP 3 )/HCOOH] system, where plasmonically generated hot electrons boost H 2 production via FADH by molecular catalysts, in distinction to the thermoplasmonic effects that seem to play a secondary role. The present H 2 -production rate data demonstrate the possibility to approach industrial-scale H 2 -production rates via FADH, using lowcost Fe-based catalysts and no sacrificial cocatalysts. We consider that the phenomenon exemplified herein for a standard molecularcatalysis system, such as [(Fe/PP 3 )/HCOOH], can be valid for many other pertinent molecular FADH catalysts.

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“…33 Unlike other carbon-based materials, e.g., Graphene Oxide 34 and graphitized biochar materials, 35 no XRD-signal at diffraction angles 10−15 or 25− 28°, that can be assigned to graphitic C (sp 2 ) is detected. 35 This shows that even in the case of C 7 −SiO 2 , the amount and size of carbon layers are very low to generate resolvable XRD diffraction. HRTEM, Figure 3, confirms that in C 7 −SiO 2 , subnanometric carbon spots are deposited on the Si matrix; however, their tiny size precludes the formation of detectable XRD patterns.…”

Section: Characterization Of the Engineered C−siomentioning

confidence: 99%

Carbon–SiO₂ Hybrid Nanoparticles with Enhanced Radical Stabilization and Biocide Activity

Fragou,

Zindrou,

Deligiannakis

et al. 2023

ACS Appl. Nano Mater.

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Nanocarbon and nanosilica are widely-used nanomaterials of significant industrial interest. Herein, a library of {carbon–SiO2} hybrid nanoparticles, with controlled nanocarbon content and sp3/sp2 profile, was engineered by a flame spray pyrolysis (FSP) process in one step. Their structure–function relationship was evaluated by studying their radical-generation and radical-stabilization activities, using electron paramagnetic resonance spectroscopy in tandem with their biocide activity toward marine bacteria Aliivibrio fischeri. The surface properties of the C–SiO2 hybrids were studied by Raman spectroscopy and surface-charge analysis by zeta potential measurements. Raman spectroscopy indicates that the FSP process, as designed and used herein, allows the progressive incorporation of nanocarbon moieties into the SiO2 nanostructure, which may lead to distortion of the siloxane matrix. Concurrently, the C–SiO2 hybrids’ surface charge profile reveals a trend correlated with the acute biocide activity toward Aliiv. fischeri. Interestingly, we find no correlation between the stable radical population and the nanohybrids’ biocide activity. Within this context, we discuss the role of surface charge, radical properties, and SiO2 lattice distortions by the nanocarbon, all of them parametrized via FSP process protocols. Thus, the present study’s findings provide critical insight into the structure–biocide activity relationship of carbon–SiO2 hybrid nanoparticles. Technology-wise, the present work exemplifies a scalable FSP process for the industrial production of applied nanomaterials, such as C–SiO2 nanostructures.

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Biochar as supporting material for heterogeneous Mn(II) catalysts: Efficient olefins epoxidation with H2O2

Cited by 16 publications

References 26 publications

Reversible Plasmonic Switch in a Molecular Oxidation Catalysis Process

Reversible Plasmonic Switch in a Molecular Oxidation Catalysis Process

Controlled Photoplasmonic Enhancement of H₂ Production via Formic Acid Dehydrogenation by a Molecular Fe Catalyst

Carbon–SiO₂ Hybrid Nanoparticles with Enhanced Radical Stabilization and Biocide Activity

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Biochar as supporting material for heterogeneous Mn(II) catalysts: Efficient olefins epoxidation with H2O2

Cited by 16 publications

References 26 publications

Reversible Plasmonic Switch in a Molecular Oxidation Catalysis Process

Reversible Plasmonic Switch in a Molecular Oxidation Catalysis Process

Controlled Photoplasmonic Enhancement of H2 Production via Formic Acid Dehydrogenation by a Molecular Fe Catalyst

Carbon–SiO2 Hybrid Nanoparticles with Enhanced Radical Stabilization and Biocide Activity

Contact Info

Product

Resources

About

Controlled Photoplasmonic Enhancement of H₂ Production via Formic Acid Dehydrogenation by a Molecular Fe Catalyst

Carbon–SiO₂ Hybrid Nanoparticles with Enhanced Radical Stabilization and Biocide Activity