Publications by authors named "Jacob Olchowka"

11 Publications

  • Page 1 of 1

Controlled Nanostructuration of Cobalt Oxyhydroxide Electrode Material for Hybrid Supercapacitors.

Materials (Basel) 2021 Apr 29;14(9). Epub 2021 Apr 29.

CNRS, University of Bordeaux, Bordeaux INP, ICMCB UMR CNRS #5026, F-33600 Pessac, France.

Nanostructuration is one of the most promising strategies to develop performant electrode materials for energy storage devices, such as hybrid supercapacitors. In this work, we studied the influence of precipitation medium and the use of a series of 1-alkyl-3-methylimidazolium bromide ionic liquids for the nanostructuration of β(III) cobalt oxyhydroxides. Then, the effect of the nanostructuration and the impact of the different ionic liquids used during synthesis were investigated in terms of energy storage performances. First, we demonstrated that forward precipitation, in a cobalt-rich medium, leads to smaller particles with higher specific surface areas (SSA) and an enhanced mesoporosity. Introduction of ionic liquids (ILs) in the precipitation medium further strongly increased the specific surface area and the mesoporosity to achieve well-nanostructured materials with a very high SSA of 265 m/g and porosity of 0.43 cm/g. Additionally, we showed that ILs used as surfactant and template also functionalize the nanomaterial surface, leading to a beneficial synergy between the highly ionic conductive IL and the cobalt oxyhydroxide, which lowers the resistance charge transfer and improves the specific capacity. The nature of the ionic liquid had an important influence on the final electrochemical properties and the best performances were reached with the ionic liquid containing the longest alkyl chain.
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http://dx.doi.org/10.3390/ma14092325DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8124577PMC
April 2021

Ionothermal Synthesis of Polyanionic Electrode Material NaV(PO)FO through a Topotactic Reaction.

Inorg Chem 2020 Dec 13;59(23):17282-17290. Epub 2020 Nov 13.

CNRS, Univ. Bordeaux, Bordeaux INP, ICMCB UMR 5026, F-33600, Pessac, France.

Polyanionic NaV(PO)FO has been successfully prepared for the first time by ionothermal reaction in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) ionic liquid. Its structure and elemental stoichiometry are confirmed by X-ray diffraction, NMR spectroscopy, and ICP-OES, respectively. Furthermore, the scanning electron microscopy reveals that the as-obtained material possesses an original platelet-like morphology. A topochemical reaction mechanism is proposed to explain the formation of the 3D framework of NaV(PO)FO from layered compound α-VOPO·2HO. Galvanostatic electrochemical tests indicate a modification of the desodiation and sodiation mechanism of the as-prepared NaV(PO)FO compared to those synthesized by conventional solid-state approaches. Furthermore, the electrochemical performance of NaV(PO)FO obtained at different cycling rates is also discussed.
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http://dx.doi.org/10.1021/acs.inorgchem.0c02546DOI Listing
December 2020

Monitoring the Crystal Structure and the Electrochemical Properties of Na(VO)(PO)F through Fe Substitution.

ACS Appl Mater Interfaces 2019 Oct 11;11(42):38808-38818. Epub 2019 Oct 11.

CNRS, Univ. Bordeaux, Bordeaux INP, ICMCB UMR 5026 , F-33600 Pessac , France.

We here present the synthesis of a new material, Na(VO)Fe(PO)F, by the sol-gel method. Its atomic and electronic structural descriptions are determined by a combination of several diffraction and spectroscopy techniques such as synchrotron X-ray powder diffraction and synchrotron X-ray absorption spectroscopy at V and Fe K edges, Fe Mössbauer, and P solid-state nuclear magnetic resonance spectroscopy. The crystal structure of this newly obtained phase is similar to that of Na(VO)(PO)F, with a random distribution of Fe ions over vanadium sites. Even though Fe and V ions situate on the same crystallographic position, their local environment can be studied separately using Fe Mössbauer and X-ray absorption spectroscopy at Fe and V K edges, respectively. The Fe ion resides in a symmetric octahedral environment, while the octahedral site of V is greatly distorted due to the presence of the vanadyl bond. No electrochemical activity of the Fe/Fe redox couple is detected, at least up to 5 V, whereas the reduction of Fe to Fe has been observed at ∼1.5 V versus Na/Na through the insertion of 0.5 Na into Na(VO)Fe(PO)F. Comparing to Na(VO)(PO)F, the electrochemical profile of Na(VO)Fe(PO)F in the same cycling condition shows a smaller polarization which could be due to a slight improvement in Na diffusion process thanks to the presence of Fe in the framework. Furthermore, the desodiation mechanism occurring upon charging is investigated by operando synchrotron X-ray diffraction and operando synchrotron X-ray absorption at V K edge.
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http://dx.doi.org/10.1021/acsami.9b14249DOI Listing
October 2019

Aluminum substitution for vanadium in the NaV(PO)F and NaV(PO)FO type materials.

Chem Commun (Camb) 2019 Sep;55(78):11719-11722

CNRS, Univ. Bordeaux, Bordeaux INP, ICMCB UMR 5026, F-33600, Pessac, France. and RS2E, Réseau Français sur le Stockage Electrochimique de l'Energie, FR CNRS 3459, F-80039 Amiens Cedex 1, France and ALISTORE-ERI European Research Institute, FR CNRS 3104, Amiens, F-80039 Cedex 1, France.

Among the positive electrode materials for Na-ion batteries, Na3V2(PO4)2F3 is considered as one of the most promising and generates high interest. Here, we study the influence of the sol-gel synthesis parameters on the structure and on the electrochemical signature of the partially substituted Na3V2-zAlz(PO4)2(F,O)3 materials. We demonstrate that the acidity of the starting solution influences the vanadium oxidation state of the final product. For the first time we report on the possibility of controlling the double Al/V and O/F substitution that leads to the preparation of the Na3V2-zAlz(PO4)2F1+zO2-z solid solution.
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http://dx.doi.org/10.1039/c9cc05137fDOI Listing
September 2019

Identification and optical features of the PbLnO series (Ln = La, Gd, Sm, Nd); genuine 2D-van der Waals oxides.

Chem Commun (Camb) 2019 Mar;55(20):2944-2947

Université Lille, CNRS, Centrale Lille, ENSCL, Université Artois, UMR 8181, Unité de Catalyse et Chimie du Solide, Lille, F-59000, France.

We report on the identification and survey of the Pb4Ln2O7 series (Ln = La, Gd, Sm and Nd) which turn out to be real van der Waals 2D oxides. In the neutral layers, strong covalent Pb-O bonds together with external stereoactive Pb2+ lone pairs, which act as sensitizers, lead to an ideal matrix for enhanced and tunable luminescence by lanthanide emitters, tested here for Sm3+ and Eu3+ doping. DFT calculations and preliminary ex-solution experiments validate the weak bonding between the layers separated by 3.5 Å and suggest a indirect to direct crossover realized by isolating the layers.
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http://dx.doi.org/10.1039/c8cc07707jDOI Listing
March 2019

The influence of ionothermal synthesis using BmimBF as a solvent on nanophosphor BaFBr:Eu photoluminescence.

Nanoscale 2018 Nov;10(42):19706-19710

Département de Chimie-Physique, Université de Genève, CH-1211 Geneva 4, Switzerland.

Ionothermal synthesis is a strongly growing research area due to the outstanding physical and chemical properties of ionic liquids (ILs) in the design of new materials, however, the interaction of these IL molecules with optical materials and their effect on the luminescence properties of the materials are poorly known. In this work, it is shown that the imidazolium based BmimBF4 ionic liquid, used as a solvent during the synthesis, tethers at the surface of the nanoparticles and influences the photoluminescence of the nanophosphor BaFBr:Eu2+ materials. In time resolved spectra, two different emissions are observed for the material synthesized by the ionothermal approach, one corresponding to Eu(ii) 5d-4f transitions in the BaFBr host with a decay time of 843 ns and the other with a much faster decay time compared to the ionic liquid BmimBF4.
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http://dx.doi.org/10.1039/c8nr06842aDOI Listing
November 2018

Facile Ionic Liquid-Assisted Strategy for Direct Precipitation of Eu -Activated Nanophosphors under Ambient Conditions.

Small 2018 04 24;14(17):e1703707. Epub 2018 Mar 24.

Inorganic Chemistry, School of Science and Technology, University of Siegen, Adolf-Reichwein-Str. 2, 57068, Siegen, Germany.

This work describes a novel ionic liquid (IL)-assisted synthesis strategy for a direct and easy production of Eu -doped nanoparticles (NPs), where ILs are also used as fluoride sources to avoid the use of elemental fluorine or toxic hydrofluoric acid. Up to now, the direct synthesis of Eu -doped nanophosphors consisted of an enormous challenge, due to the oxidation to Eu observed in hydrous solution, which is commonly used for the preparation of NPs, generating lattice defects and undesired particle growth or agglomeration by additional reducing steps at high temperatures. In contrast, ILs, unless containing ClO or NO anions, do not present an oxidizing character, allowing the direct precipitation of NPs, e.g., using Eu containing starting materials. Here, the undoped and Eu -doped BaFCl NPs have been prepared under atmospheric conditions for the first time using ILs as solvents and also as fluoride source, applying sonochemical and microwave-assisted approaches. In general, this method bears an enormous potential for an easy synthesis of fluoride materials compared to inconvenient solid-state methods. In addition, the IL plays the role of a strongly attached protecting shell which represents ≈7-8% of the total NPs weight.
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http://dx.doi.org/10.1002/smll.201703707DOI Listing
April 2018

Green Synthesis of A SiF (A=Li-Cs) Nanoparticles using Ionic Liquids as Solvents and as Fluorine Sources: A Simple Approach without HF.

Chemistry 2017 Sep 26;23(50):12092-12095. Epub 2017 Jul 26.

Department of Chemistry and Biology, University of Siegen, Adolf-Reichwein-Str. 2, 57068, Siegen, Germany.

In this Communication, nanoparticles of the fluoridosilicates A SiF (A=Li, Na, K, Rb, Cs), which are extremely promising host lattices for future LEDs, are presented for the first time. The preparation method we introduce here is a very simple and energy and time saving one, moreover the usage of toxic HF or elemental fluorine is avoided. In detail, the ionic liquid [Bmim]PF was used both as solvent and fluoride source in an ionothermally assisted microwave synthesis. The small size of the so-obtained nanoparticles is of huge relevance for their applications as thin films or for the coverage of surfaces, for example in next-generation white LEDs upon doping with Mn .
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http://dx.doi.org/10.1002/chem.201702375DOI Listing
September 2017

Decay times of the spin-forbidden and spin-enabled transitions of Yb doped in CsCaX and CsSrX (X = Cl, Br, I).

Phys Chem Chem Phys 2017 Mar;19(10):7188-7194

Inorganic Chemistry, Faculty of Science and Technology, University of Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany.

In this paper, a systematic study of the decay times of the spin-enabled and spin-forbidden transitions of Yb doped into the halidoperovskites CsMX (M = Ca, Sr; X = Cl, Br, I) is presented. The spin-forbidden transitions are characterized by ms decay times, which are typical for Yb. On the contrary, the spin-enabled transitions show much shorter decay times in the range of μs and have so far only been rarely observed. These results allow detailed conclusions about systematics of the decay times of Yb doped in similar compounds and their correlation to the local structure of the coordination sphere of Yb as well as the role of vibrational interaction between the excited high spin (HS) and low spin (LS) states. The halidoperovskites are ideally suited as host lattices in this context and may work as text book examples due to their comparable structures, which allows a detailed interpretation of the decay times in relation to the local structure. An understanding of the impact of the composition and structure of the host material on the decay times of Yb will be of relevance for future applications of this activator in scintillators or lighting materials.
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http://dx.doi.org/10.1039/c7cp00581dDOI Listing
March 2017

ABiO2X (A = Cd, Ca, Sr, Ba, Pb; X = halogen) Sillen X1 Series: Polymorphism Versus Optical Properties.

Inorg Chem 2016 Aug 14;55(15):7582-92. Epub 2016 Jul 14.

Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS - Unité de Catalyse et Chimie du Solide , F-59000 Lille, France.

The Sillen X1 series of Bi(3+)A(2+)O2X (A = Cd, Ca, Sr, Ba, Pb; X = Cl, Br, I) compounds is composed of three main crystallographic types, namely, the tetragonal form (space group (S.G.) I4/mmm), the orthorhombic form (S.G. Cmcm), and the monoclinic form (S.G. P21/m). Because of Bi(3+)/A(2+) disorder the Bi(3+) based photoluminescence (PL) of the tetragonal polytypes is quenched at room temperature (RT). In the two other ordered forms, the Bi-O-Bi connectivity is different but limited, such that bluish/greenish emission occurs at RT in the monoclinic CdBiO2Cl and CaBiO2Cl and orthorhombic SrBiO2Cl and BaBiO2Cl phases. The crystal structure of BaBiO2Br was refined in the orthorhombic Cmcm space group and also shows RT emission. Focusing on the RT luminescent activity as a key parameter, the PL active compounds were investigated by means of density functional theory calculations and UV-visible reflectance spectroscopy. The influence of A and X ions on the excitation energy is discussed by analyzing the A-O-Bi and Bi-X bonding schemes and gives some insights for rational tuning of both the excitation and emission energies.
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http://dx.doi.org/10.1021/acs.inorgchem.6b01024DOI Listing
August 2016

Multidimensional open-frameworks: combinations of one-dimensional channels and two-dimensional layers in novel BI/M oxo-chlorides.

Inorg Chem 2014 Jan 12;53(1):528-36. Epub 2013 Dec 12.

Université Lille Nord de France , UMR 8181 CNRS, Unité de Catalyse et de Chimie du Solide (UCCS USTL), F-59655 Villeneuve d'Ascq, France.

Here we discuss the synthesis and characterization of three novel bismuth oxo-chlorides ([Bi6Na0.5O7.5][Na0.5Cl3]channel[Cl]layer; [Bi17PbO22][Cl6]channel[Cl3]layer; [Bi9(Pb0.2Mn0.8)O12][Cl3]channel [Cl2]layer) which all show an original multidimensional crystal structure. It is formed of two-dimensional (2D)-layered blocks separated by Cl(-) layers. The blocks are porous with triangular one-dimensional (1D)-Cl(-) channels with various section sizes. This multidimensional feature is unique in the field of Bi and Pb oxo-halides, while so far only 1D or 2D halides units have been reported. The stability of the framework is allowed by Bi(3+)/M(n+) aliovalent substitution to balance charge neutrality. The channel and tunnel walls are formed by edge-sharing O(Bi,M)4 oxocentered tetrahedra, while the triangular tunnel junctions are achieved by O(Bi,M)5 pyramids. The three compounds are rather stable, but only [Bi6Na0.5O7.5][Na0.5Cl3]tunnel[Cl]layer was obtain as a single-phase material so that its photoluminecence properties have been investigated. It shows an unusual red bright luminescence with a maximum at 14150 cm(-1) at low temperatures due to Bi(3+) transitions that are well explained by the Bi-Cl bonding scheme.
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http://dx.doi.org/10.1021/ic402578mDOI Listing
January 2014