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Piotr Krawczyk - One of the best experts on this subject based on the ideXlab platform.
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influence of chemical exfoliation process on the activity of nicl2 fecl3 pdcl2 graphite Intercalation Compound towards methanol electrooxidation
Applied Catalysis B-environmental, 2018Co-Authors: Tomasz Rozmanowski, Piotr KrawczykAbstract:Abstract In the present work the influence of chemical exfoliation process of quaternary graphite Intercalation Compound (NiCl 2 -FeCl 3 -PdCl 2 -GIC) on its catalytic activity in the methanol electrooxidation reaction was examined. NiCl 2 -FeCl 3 -PdCl 2 -GIC was synthesized by a molten salts method using purified flaky graphite and anhydrous metal chlorides as reactants. The process of Intercalation was carried out at 450 °C for 72 h. To obtain exfoliated graphite Intercalation Compound (NiCl 2 -FeCl 3 -PdCl 2 -EGIC), a part of gathered product underwent chemical exfoliation in hydrogen peroxide solution. Crystalline structure of the obtained GIC and product of its exfoliation was characterized by XRD while the their morphology by SEM and TEM techniques. Development of the surface area was calculated by BET method. Electrochemical activity of both materials were examined in the model process of methanol electrooxidation by cyclic (CV) and linear sweep (LSV) voltammetry as well as potentiostatic method. The XRD and SEM analysis have showed that the chemical exfoliation process contributes to the changes in structure and morphology of the examined material. From the electrochemical results it is revealed that prepared NiCl 2 -FeCl 3 -PdCl 2 -GIC exhibits activity towards electrochemical process of methanol oxidation. Furthermore is proved that electroactivity of the examined NiCl 2 -FeCl 3 -PdCl 2 -GIC significantly increases due its chemical exfoliation.
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enhancement of electrochemical hydrogen storage in nicl2 fecl3 pdcl2 graphite Intercalation Compound effected by chemical exfoliation
Applied Surface Science, 2013Co-Authors: J M Skowronski, Tomasz Rozmanowski, Piotr KrawczykAbstract:Abstract In the present work, a quaternary NiCl2–FeCl3–PdCl2–graphite Intercalation Compound (NiCl2–FeCl3–PdCl2–GIC) was successfully synthesized by molten salts method. A part of this Compound was subsequently subjected to chemical exfoliation to obtain expanded Compound (NiCl2–FeCl3–PdCl2–EGIC). The changes created in crystalline structure, morphology and chemical composition of GIC due to exfoliation were examined by XRD, SEM and EDS techniques and then related to electrochemical behaviour of electrodes made of the original and exfoliated Compound. The results of electrochemical studies carried out by the cyclic voltammetry (CV) method in 6 M KOH solution showed that current charges of all the cathodic and anodic peaks recorded for NiCl2–FeCl3–PdCl2–EGIC are considerably higher already in the first two cycles as compared to those observed for the original NiCl2–FeCl3–PdCl2–GIC. This improvement is ascribed to chemical exfoliation leading to a tremendous development of surface area of the Compound due to the splitting and wrinkling of graphite flakes followed by easier access of hydroxyl ions of the electrolyte to active species of intercalates preserved between the graphene interspaces as well as expelled from the graphite interspacing. A large anodic peak was recorded on CV curves after the potentiostatic polarization of electrodes at the potential of −1.2 V where the reaction of hydrogen sorption/evolution occurs and intercalates highly dispersed in the graphite matrix are reduced to a metal form. This peak mainly corresponding to the recovery of hydrogen stored in the electrode appeared to be over five times higher for electrode made of exfoliated Compound. This significant enhancement of the hydrogen storage capacity is attributed to electrochemically active Pd nanoparticles highly dispersed in porous structure of exfoliated Compound and likely functioning in synergy with Ni/Fe clusters.
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electrochemical behavior of exfoliated nicl2 graphite Intercalation Compound affected by hydrogen sorption
Energy Conversion and Management, 2008Co-Authors: J M Skowronski, Piotr Krawczyk, Tomasz Rozmanowski, Jan UrbaniakAbstract:Abstract The aim of this investigation was to examine the processes occurring in alkaline solution for electrodes made of graphite Intercalation Compound with nickel chloride (NiCl2–GIC) and exfoliated graphite Intercalation Compound with nickel chloride (NiCl2–EGIC). On the contrary to most acceptor graphite Intercalation Compounds (GICs), which are easily exfoliated upon heat treatment, NiCl2–GIC appeared to be thermally resistant even if the process was carried out at very high temperatures. Exfoliation of NiCl2–GIC was succeeded at room temperature by chemical method in the solution of hydrogen peroxide. The effects of exfoliation were examined by XRD and SEM techniques. As shown by these techniques, after exfoliation a part of NiCl2 intercalate persisted in the graphite lattice. Using the cyclic voltammetry method it was shown that the process of electrochemical reduction occurring for electrode made of NiCl2–EGIC differs significantly from that for the original NiCl2–GIC. The conversion of NiCl2–GIC to NiCl2–EGIC reveals new possibilities of practical use of the electrode, in which the Ni(II) → Ni reduction reaction and hydrogen sorption occur simultaneously. The obtained results have shown that the anodic charge increases on increasing the time of hydrogen sorption at a given potential and on decreasing the potential of hydrogen sorption. From comparison, one can conclude that the surplus charge measured during the anodic run is associated with the oxidation reaction of hydrogen stored in NiCl2–EGIC during the precedent reduction reaction resulting in the generation of electrochemically active nickel clusters in exfoliated graphite matrix. It was shown that the diffusion rate of hydrogen ions to/in the structure of NiCl2–EGIC exerts important influence on the kinetics of hydrogen storage.
Tomasz Rozmanowski - One of the best experts on this subject based on the ideXlab platform.
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influence of chemical exfoliation process on the activity of nicl2 fecl3 pdcl2 graphite Intercalation Compound towards methanol electrooxidation
Applied Catalysis B-environmental, 2018Co-Authors: Tomasz Rozmanowski, Piotr KrawczykAbstract:Abstract In the present work the influence of chemical exfoliation process of quaternary graphite Intercalation Compound (NiCl 2 -FeCl 3 -PdCl 2 -GIC) on its catalytic activity in the methanol electrooxidation reaction was examined. NiCl 2 -FeCl 3 -PdCl 2 -GIC was synthesized by a molten salts method using purified flaky graphite and anhydrous metal chlorides as reactants. The process of Intercalation was carried out at 450 °C for 72 h. To obtain exfoliated graphite Intercalation Compound (NiCl 2 -FeCl 3 -PdCl 2 -EGIC), a part of gathered product underwent chemical exfoliation in hydrogen peroxide solution. Crystalline structure of the obtained GIC and product of its exfoliation was characterized by XRD while the their morphology by SEM and TEM techniques. Development of the surface area was calculated by BET method. Electrochemical activity of both materials were examined in the model process of methanol electrooxidation by cyclic (CV) and linear sweep (LSV) voltammetry as well as potentiostatic method. The XRD and SEM analysis have showed that the chemical exfoliation process contributes to the changes in structure and morphology of the examined material. From the electrochemical results it is revealed that prepared NiCl 2 -FeCl 3 -PdCl 2 -GIC exhibits activity towards electrochemical process of methanol oxidation. Furthermore is proved that electroactivity of the examined NiCl 2 -FeCl 3 -PdCl 2 -GIC significantly increases due its chemical exfoliation.
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enhancement of electrochemical hydrogen storage in nicl2 fecl3 pdcl2 graphite Intercalation Compound effected by chemical exfoliation
Applied Surface Science, 2013Co-Authors: J M Skowronski, Tomasz Rozmanowski, Piotr KrawczykAbstract:Abstract In the present work, a quaternary NiCl2–FeCl3–PdCl2–graphite Intercalation Compound (NiCl2–FeCl3–PdCl2–GIC) was successfully synthesized by molten salts method. A part of this Compound was subsequently subjected to chemical exfoliation to obtain expanded Compound (NiCl2–FeCl3–PdCl2–EGIC). The changes created in crystalline structure, morphology and chemical composition of GIC due to exfoliation were examined by XRD, SEM and EDS techniques and then related to electrochemical behaviour of electrodes made of the original and exfoliated Compound. The results of electrochemical studies carried out by the cyclic voltammetry (CV) method in 6 M KOH solution showed that current charges of all the cathodic and anodic peaks recorded for NiCl2–FeCl3–PdCl2–EGIC are considerably higher already in the first two cycles as compared to those observed for the original NiCl2–FeCl3–PdCl2–GIC. This improvement is ascribed to chemical exfoliation leading to a tremendous development of surface area of the Compound due to the splitting and wrinkling of graphite flakes followed by easier access of hydroxyl ions of the electrolyte to active species of intercalates preserved between the graphene interspaces as well as expelled from the graphite interspacing. A large anodic peak was recorded on CV curves after the potentiostatic polarization of electrodes at the potential of −1.2 V where the reaction of hydrogen sorption/evolution occurs and intercalates highly dispersed in the graphite matrix are reduced to a metal form. This peak mainly corresponding to the recovery of hydrogen stored in the electrode appeared to be over five times higher for electrode made of exfoliated Compound. This significant enhancement of the hydrogen storage capacity is attributed to electrochemically active Pd nanoparticles highly dispersed in porous structure of exfoliated Compound and likely functioning in synergy with Ni/Fe clusters.
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electrochemical behavior of exfoliated nicl2 graphite Intercalation Compound affected by hydrogen sorption
Energy Conversion and Management, 2008Co-Authors: J M Skowronski, Piotr Krawczyk, Tomasz Rozmanowski, Jan UrbaniakAbstract:Abstract The aim of this investigation was to examine the processes occurring in alkaline solution for electrodes made of graphite Intercalation Compound with nickel chloride (NiCl2–GIC) and exfoliated graphite Intercalation Compound with nickel chloride (NiCl2–EGIC). On the contrary to most acceptor graphite Intercalation Compounds (GICs), which are easily exfoliated upon heat treatment, NiCl2–GIC appeared to be thermally resistant even if the process was carried out at very high temperatures. Exfoliation of NiCl2–GIC was succeeded at room temperature by chemical method in the solution of hydrogen peroxide. The effects of exfoliation were examined by XRD and SEM techniques. As shown by these techniques, after exfoliation a part of NiCl2 intercalate persisted in the graphite lattice. Using the cyclic voltammetry method it was shown that the process of electrochemical reduction occurring for electrode made of NiCl2–EGIC differs significantly from that for the original NiCl2–GIC. The conversion of NiCl2–GIC to NiCl2–EGIC reveals new possibilities of practical use of the electrode, in which the Ni(II) → Ni reduction reaction and hydrogen sorption occur simultaneously. The obtained results have shown that the anodic charge increases on increasing the time of hydrogen sorption at a given potential and on decreasing the potential of hydrogen sorption. From comparison, one can conclude that the surplus charge measured during the anodic run is associated with the oxidation reaction of hydrogen stored in NiCl2–EGIC during the precedent reduction reaction resulting in the generation of electrochemically active nickel clusters in exfoliated graphite matrix. It was shown that the diffusion rate of hydrogen ions to/in the structure of NiCl2–EGIC exerts important influence on the kinetics of hydrogen storage.
Ikpyo Hong - One of the best experts on this subject based on the ideXlab platform.
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preparation of the spheroidized graphite derived multi layered graphene via gic graphite Intercalation Compound method
Journal of Industrial and Engineering Chemistry, 2017Co-Authors: Eunjung Lee, Ikpyo HongAbstract:Abstract Artificially spheroidized natural graphite (SNG) was processed to obtain expanded graphite and graphene nanoplatelets using GIC (graphite Intercalation Compound)-assisted exfoliation process. Sulfuric acid and hydrogen peroxide were used as the intercalant and oxidant for the GIC formation, respectively. SNG was successfully converted into both expanded graphite and graphene nanoplatelets. Degree of exfoliation of the produced graphene nanoplatelets was found to be proportional to the average diameter of starting materials. Graphene nanoplatelets prepared from SNG with average diameter of 50 μm were analyzed to have the averaged lateral size of 45.4 μm at the thickness of ca. 5 nm.
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preparation of kish graphite based graphene nanoplatelets by gic graphite Intercalation Compound via process
Journal of Industrial and Engineering Chemistry, 2015Co-Authors: Jungchul An, Ikpyo HongAbstract:Abstract Several-micrometer-wide at a few-nanometer-thick graphene platelets were successfully prepared from Kish graphite by simple GIC (graphite Intercalation Compound) via exfoliation process. High crystalline Kish graphite flakes were recovered from the steelmaking by-product using the modified beneficiation process. Sulfuric acid was served as the functional intercalating agent in the GIC formation step. XRD results revealed the stable and clear first-stage state formed in the acid-intercalated GIC. Carbon content in the recovered Kish graphite was found to influence the average thickness of prepared graphene nanoplatelets. Larger Kish graphite flakes were also beneficial to produce thin graphene platelets with the average thickness of 5 nm.
J M Skowronski - One of the best experts on this subject based on the ideXlab platform.
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enhancement of electrochemical hydrogen storage in nicl2 fecl3 pdcl2 graphite Intercalation Compound effected by chemical exfoliation
Applied Surface Science, 2013Co-Authors: J M Skowronski, Tomasz Rozmanowski, Piotr KrawczykAbstract:Abstract In the present work, a quaternary NiCl2–FeCl3–PdCl2–graphite Intercalation Compound (NiCl2–FeCl3–PdCl2–GIC) was successfully synthesized by molten salts method. A part of this Compound was subsequently subjected to chemical exfoliation to obtain expanded Compound (NiCl2–FeCl3–PdCl2–EGIC). The changes created in crystalline structure, morphology and chemical composition of GIC due to exfoliation were examined by XRD, SEM and EDS techniques and then related to electrochemical behaviour of electrodes made of the original and exfoliated Compound. The results of electrochemical studies carried out by the cyclic voltammetry (CV) method in 6 M KOH solution showed that current charges of all the cathodic and anodic peaks recorded for NiCl2–FeCl3–PdCl2–EGIC are considerably higher already in the first two cycles as compared to those observed for the original NiCl2–FeCl3–PdCl2–GIC. This improvement is ascribed to chemical exfoliation leading to a tremendous development of surface area of the Compound due to the splitting and wrinkling of graphite flakes followed by easier access of hydroxyl ions of the electrolyte to active species of intercalates preserved between the graphene interspaces as well as expelled from the graphite interspacing. A large anodic peak was recorded on CV curves after the potentiostatic polarization of electrodes at the potential of −1.2 V where the reaction of hydrogen sorption/evolution occurs and intercalates highly dispersed in the graphite matrix are reduced to a metal form. This peak mainly corresponding to the recovery of hydrogen stored in the electrode appeared to be over five times higher for electrode made of exfoliated Compound. This significant enhancement of the hydrogen storage capacity is attributed to electrochemically active Pd nanoparticles highly dispersed in porous structure of exfoliated Compound and likely functioning in synergy with Ni/Fe clusters.
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electrochemical behavior of exfoliated nicl2 graphite Intercalation Compound affected by hydrogen sorption
Energy Conversion and Management, 2008Co-Authors: J M Skowronski, Piotr Krawczyk, Tomasz Rozmanowski, Jan UrbaniakAbstract:Abstract The aim of this investigation was to examine the processes occurring in alkaline solution for electrodes made of graphite Intercalation Compound with nickel chloride (NiCl2–GIC) and exfoliated graphite Intercalation Compound with nickel chloride (NiCl2–EGIC). On the contrary to most acceptor graphite Intercalation Compounds (GICs), which are easily exfoliated upon heat treatment, NiCl2–GIC appeared to be thermally resistant even if the process was carried out at very high temperatures. Exfoliation of NiCl2–GIC was succeeded at room temperature by chemical method in the solution of hydrogen peroxide. The effects of exfoliation were examined by XRD and SEM techniques. As shown by these techniques, after exfoliation a part of NiCl2 intercalate persisted in the graphite lattice. Using the cyclic voltammetry method it was shown that the process of electrochemical reduction occurring for electrode made of NiCl2–EGIC differs significantly from that for the original NiCl2–GIC. The conversion of NiCl2–GIC to NiCl2–EGIC reveals new possibilities of practical use of the electrode, in which the Ni(II) → Ni reduction reaction and hydrogen sorption occur simultaneously. The obtained results have shown that the anodic charge increases on increasing the time of hydrogen sorption at a given potential and on decreasing the potential of hydrogen sorption. From comparison, one can conclude that the surplus charge measured during the anodic run is associated with the oxidation reaction of hydrogen stored in NiCl2–EGIC during the precedent reduction reaction resulting in the generation of electrochemically active nickel clusters in exfoliated graphite matrix. It was shown that the diffusion rate of hydrogen ions to/in the structure of NiCl2–EGIC exerts important influence on the kinetics of hydrogen storage.
V G Storchak - One of the best experts on this subject based on the ideXlab platform.
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Topotactic synthesis of the overlooked multilayer silicene Intercalation Compound SrSi2
Nanoscale, 2016Co-Authors: Andrey M. Tokmachev, D. V. Averyanov, I. A. Karateev, O. E. Parfenov, S. N. Yakunin, Alexander L. Vasiliev, V G StorchakAbstract:Silicene, a 2D honeycomb lattice of Si atoms similar to graphene, is expected to be a platform for nanoelectronics and home to novel quantum phenomena. Unlike graphene, free-standing silicene is notoriously difficult to stabilize, while strong hybridization of silicene with substrates destroys its desirable properties. On the other hand, Dirac cones of silicene are effectively realized in a bulk – stoichiometric ionic multilayer silicene Intercalation Compound CaSi2. Besides, a number of new 2D silicene-based materials are synthesized employing CaSi2 as a precursor. However, the rather complex atomic structure of CaSi2 and fresh opportunities of physical and chemical breakthroughs drive the search for alternative Compounds with silicene networks. Here, a new polymorph of SrSi2 is synthesized, enjoying both the structure of intercalated multilayer silicene and the simplest possible stacking of silicene sheets. The MBE-quality synthesis accomplished on Si(001) and Si(111) surfaces leads to epitaxial films of SrSi2 with orientation controlled by the substrate, as revealed by XRD, RHEED and electron microscopy studies. The structural SrSi2/Si relation is mirrored in the transport properties of the films.