Researcher:
Barım, Şansım Bengisu

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Şansım Bengisu

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Barım

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Barım, Şansım Bengisu

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2017 - 201932020 - 20225

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    Graphene aerogel supported pt electrocatalysts for oxygen reduction reaction by supercritical deposition
    (Elsevier, 2017) Yu, Haibo; Aindow, Mark; N/A; N/A; N/A; Department of Chemistry; Department of Chemical and Biological Engineering; Öztuna, Feriha Eylül Saraç; Barım, Şansım Bengisu; Bozbağ, Selmi Erim; Ünal, Uğur; Erkey, Can; PhD Student; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Chemistry; Department of Chemical and Biological Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; N/A; N/A; 42079; 29633
    Mesoporous graphene aerogel (GA) supported Pt nanoparticles with narrow size distribution were prepared via supercritical deposition (SCD) using supercritical CO2 (scCO(2)). Pt(cod)me(2) precursor was dissolved in scCO(2) and adsorbed onto GA at 35 degrees C and 10.7 MPa. The Pt precursor was converted to its metal form under atmospheric pressure at various temperatures. The effects of precursor conversion temperature (400, 600, and 800 degrees C) on the structural properties of the composites were investigated using Raman Spectroscopy, XRD, XPS, and TEM. The average particle size increased from 1.2 to 2.9 nm when the conversion temperature was increased from 400 to 800 degrees C. The electrocatalytic activity of the samples towards the Oxygen Reduction Reaction were evaluated using cyclic voltammetry (CV) and rotating disc electrode (RDE) measurements. SCD helped to preserve the textural properties of the GA after the Pt nanoparticle deposition, and thus Pt/GA converted at 600 degrees C exhibited an enhanced mass activity of 30.6 mA mg(Pt)(-1), outperforming the mass activities reported in the literature for Pt/GA electrocatalysts prepared using conventional routes. (C) 2017 Elsevier Ltd. All rights reserved.
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    Mesoporous carbon aerogel supported PtCu bimetallic nanoparticles via supercritical deposition and their dealloying and electrocatalytic behaviour
    (Elsevier Science Bv, 2018) Yu, Haibo; Kızılel, Rıza; Aindow, Mark; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Barım, Şansım Bengisu; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Researcher; Faculty Member; Department of Chemical and Biological Engineering; N/A; College of Engineering; College of Engineering; N/A; N/A; 29633
    Mesoporous carbon aerogel (CA) supported PtCu bimetallic nanoparticles were prepared via a sequential supercritical deposition (SCD) method using supercritical carbon dioxide (scCO(2)). The effects of deposition order of the metal, annealing temperature and metal composition on the average PtCu particle size, size distribution and dispersion were investigated. Four sets of PtCu/CA samples were prepared with two Pt:Cu molar ratios (1:1 and 1:3) and with two different deposition orders (i.e. either Pt or Cu first). X-ray diffraction and electron microscopy data showed that all of the as-prepared samples formed homogeneously distributed disordered PtCu alloy nanoparticles with narrow particle size distributions on the CA support. Increasing annealing temperature in the range 600-950 degrees C increased the average particle size from 1.8 nm to 4.5 nm and resulted in the elimination of separate Cu nanoparticles on the CA surface. The dealloying of the supported PtCu nanoparticles were carried out by cyclic voltammetry and the activity of the dealloyed nanoparticles (after 300 potential cycles) towards the oxygen reduction reaction (ORR) was investigated using rotating disc electrode (RDE) experiments. During dealloying, peaks associated with bulk dissolution and deposition of Cu and dissolution and re-deposition of Cu from the alloyed PtCu nanoparticles were observed at initial cycles along with peaks associated with creation of new Pt sites. Supported nanoparticles with Pt: Cu molar ratios of 1:1 and 1:3 which were prepared by deposition of Cu first had low activities towards ORR after dealloying. on the contrary, nanoparticles prepared by depositing Pt first exhibited promising electrocatalytic activities after dealloying. Samples with a Pt: Cu molar ratio of 1:3 showed higher activities than those with a molar ratio of 1:1. An enhanced ESA of 137 m(2)/g and dealloying induced enhanced mass activity of 0.123 A/mg(Pt) was obtained using the sample with a Pt: Cu molar ratio of 1:3, which was annealed at 800 degrees C. on the other hand, the same sample annealed at 950 degrees C had the highest specific activity of 0.165 mA/cm(2).
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    Supercritical fluid reactive deposition: a process intensification technique for synthesis of nanostructured materials
    (Elsevier, 2022) Eriş, Gamze; Uzunlar, Erdal; N/A; N/A; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Yousefzadeh, Hamed; Akgün, Işık Sena; Barım, Şansım Bengisu; Sarı, Tarık Bercan; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Researcher; Researcher; PhD Student; Researcher; Faculty Member; Department of Chemical and Biological Engineering; N/A; N/A; N/A; N/A; N/A; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); N/A; N/A; N/A; Graduate School of Sciences and Engineering; N/A; College of Engineering; N/A; N/A; N/A; N/A; N/A; 29633
    Supercritical fluid reactive deposition (SFRD) is a promising process intensification technique for synthesis of a wide variety of nanostructured materials. The enhanced mass transfer characteristics of supercritical fluids (SCFs) coupled with high solubilities of reducing gases in SCFs provide many advantages related to equipment size and time minimization over conventional techniques. Among SCFs, the emphasis has been placed on supercritical CO2 (scCO(2)) which is non-toxic, cheap and leaves no residue on the treated medium. Moreover, in SFRD, multiple processes such as dissolution, adsorption, reaction, and purification are combined in a single piece of equipment which is an excellent example of process integration for process intensification. In this review, the fundamental thermodynamic and kinetic aspects of the technology are described in detail. The studies in the literature on synthesis of a wide variety of nanostructured materials including supported nanoparticles, films, and ion-exchanged zeolites by SFRD are reviewed and summarized. The applications of these materials as catalysts and sensors are described. The review hopes to lead to further studies on further development of this technology for a wide variety of applications.
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    Highly active carbon supported PtCu electrocatalysts for PEMFCs by in situ supercritical deposition coupled with electrochemical dealloying
    (Wiley-V C H Verlag Gmbh, 2020) Deljoo, B.; Aindow, M.; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Barım, Şansım Bengisu; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Researcher; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Engineering; College of Engineering; College of Engineering; N/A; N/A; 29633
    Carbon aerogel and Vulcan supported PtCu electrocatalysts were prepared using the simultaneous and sequential in situ supercritical deposition (SCD) method in supercritical CO2 followed by thermal annealing and electrochemical dealloying. Before dealloying, annealed electrocatalysts prepared by simultaneous SCD had a more uniform PtCu composition in PtCu nanoparticles whereas electrocatalysts prepared by sequential SCD led to PtCu nanoparticles with Cu enrichment on the surface. Upon dealloying, PtCu/CA electrocatalyst prepared by simultaneous SCD had an enhanced ESA of 159.4 m(2) g(-1) due to the synergistic effects of PtCu nanoparticle size and PtCu composition in nanoparticles. All dealloyed electrocatalysts had higher mass activities and PtCu/Vulcan electrocatalyst prepared by simultaneous SCD had the highest mass activity of 0.178 A mg(Pt)(-1) which was more than twice of the mass activity of commercial Pt/C. PtCu/Vulcan electrocatalyst prepared by sequential SCD showed a specific activity of 0.511 mA cm(-2) which was 5 times higher than the specific activity of commercial Pt/C.
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    Control of average particle size of carbon aerogel supported platinum nanoparticles by supercritical deposition
    (Elsevier Science Bv, 2017) Bayrakçeken, Ayşe; Zhang, Lichun; Kızılel, Rıza; Aindow, Mark; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Barım, Şansım Bengisu; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Researcher; Faculty Member; Department of Chemical and Biological Engineering; N/A; College of Engineering; College of Engineering; N/A; N/A; 29633
    Supercritical deposition was used to synthesize Pt/carbon aerogel (Pt/CA) electrocatalysts. CAs with average pore diameters of 6, 8 and 19 nm (CA6, CA8 and CA19, respectively) were synthesized and impregnated with Pt(cod)me(2) precursor using supercritical carbon dioxide followed by the thermal conversion of the Pt precursor into its metallic form under N-2 atmosphere at various temperatures between 200 and 1000 degrees C. All of the prepared CAs have high surface areas with very sharp pore size distributions. XRD and TEM results show increased Pt particle size with increasing conversion temperature with a homogenous distribution of nanoparticles on the CA supports. Cyclic voltammetry was used to determine the effect of CA pore properties on electrocatalytic activity. At a conversion temperature of 400 degrees C, the highest and lowest electrochemical surface area values were obtained for Pt/CA19 and Pt/CA6 of (126 and 36 m(2)/g, respectively). Furthermore, Pt/CA19 showed good mass activity whereas Pt/CA6 and Pt/CA8 had lower activity values towards the Oxygen Reduction Reaction (ORR). The mass activity values for Pt/CA19 increased with increasing conversion temperature, except for the sample converted at 1000 degrees C which exhibited the lowest mass activity. The specific activity increased significantly with the conversion temperature up to 600 degrees C which gave a value six times that obtained at 200 degrees C. At 800 degrees C, the specific activity decreased slightly, probably due to a change in the CA structure at this elevated conversion temperature. The Pt/CA19 sample converted at 600 degrees C exhibited the best performance with a mass activity of 0.1 A/mg(pt) and a specific activity of 0.24 mA/cm(2).
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    Polyamide aerogel-derived n-doped carbon aerogel decorated with platinum nanoparticles as highly active and stable electrocatalysts for oxygen reduction reaction
    (Pergamon-Elsevier Science Ltd, 2022) Raptapoulos, Grigorios; Rommel, Sarshad; Aindow, Mark; Paraskevopoulou, Patrina; Department of Chemical and Biological Engineering; Barım, Şansım Bengisu; Erkey, Can; Researcher; Faculty Member; Department of Chemical and Biological Engineering; N/A; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Engineering; N/A; 29633
    We prepared polyamide aerogel (PA)-derived carbon aerogel (CA) supported Pt nanoparticles with the super-critical CO2 deposition (SCD) technique as electrocatalysts for the oxygen reduction reaction (ORR). PAs were pyrolyzed at 800 degrees C to yield CPA and some CPA monoliths were subsequently etched with CO2 at 1000 degrees C to yield etched CPA (ECPA) to increase micro-mesoporosity and surface area in order to investigate their effect on the Pt nanoparticle dispersion and electrocatalytic performance towards ORR. The N-rich backbone of PAs yielded homogenously distributed N atoms in the CA structure enabling homogenous distribution of Pt nano-particles, efficient dispersion of the Nafion ionomer and possible creation of ORR-active sites. Highly dispersed Pt nanoparticles with average size of 1.5 and 3.0 nm were obtained on CPA and ECPA, respectively. Pt-ECPA electrocatalysts showed enhanced electrochemically active surface area (ESA) and ORR mass activity when compared with commercial Pt-C. Pt-CPA showed similar ESA, mass and specific activity to that of commercial Pt-C due to lower mesopore volume and higher average Pt nanoparticle size. Accelerated stability tests (AST) revealed superior stability of Pt-CPA electrocatalyst due to favorable initial Pt nanoparticle size enabling suc-cessful immobilization Pt nanoparticles on CPA through the N-functionalities. Two important parameters, pore structure of carbon aerogel and initial Pt nanoparticle size, can be controlled through the powerful combination of sol-gel and supercritical deposition techniques to achieve both highly active and stable electerocatalysts.
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    PublicationOpen Access
    Review-supercritical deposition: a powerful technique for synthesis of functional materials for electrochemical energy conversion and storage
    (Electrochemical Society (ECS), 2020) Uzunlar, Erdal; Department of Chemical and Biological Engineering; Erkey, Can; Barım, Şansım Bengisu; Bozbağ, Selmi Erim; Faculty Member; Researcher; Researcher; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Engineering; Graduate School of Sciences and Engineering; 29633; N/A; N/A
    Supercritical fluid-based technologies are increasingly being used to develop novel functional nanostructured materials or improve the properties of existing ones. Among these, supercritical deposition (SCD) is an emerging technique to incorporate metals on supports. It has been used to deposit a wide variety of single or multi-metallic morphologies such as highly dispersed species, nanoparticles, nanorods and conformal films on high surface area supports, polymers and crystalline substrates. SCD is also attracting increasing attention for preparation of micro or nano-architectured functional materials in a highly controllable manner for electrochemical energy conversion and storage systems. Increasing number of studies in the literature demonstrates that materials synthesized using SCD are comparable or superior in performance as compared to their conventional counterparts. In this review, an overview of the fundamentals of the SCD technique is presented. Properties of a wide variety of nanostructured functional materials such as supported nanoparticles and films prepared using SCD for electrochemical applications are summarized. The electrochemical performance of these materials in electrochemical tests and also in fuel cells, electrolyzers and Li-ion batteries are also presented.
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    PublicationOpen Access
    A remarkable class of nanocomposites: aerogel supported bimetallic nanoparticles
    (Frontiers, 2020) Özbakır, Yaprak; Department of Chemical and Biological Engineering; Güneş, Hande; Barım, Şansım Bengisu; Yousefzadeh, Hamed; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; 29633
    Aerogels are a unique class of materials due to their low density, high porosity, high surface area, and an open and interconnected pore structure. Aerogels can be organic, inorganic and hybrid with a plethora of surface chemistries. Aerogel-based products for thermal insulation are already in the market and many studies are being conducted in many laboratories around the world to develop aerogel-based products for other applications including catalysis, adsorption, separations, and drug delivery. On the other hand, bimetallic nanoparticles dispersed on high surface area carriers, which have superior properties compared to their monometallic counterparts, are used or are in development for a wide variety of applications in catalysis, optics, sensing, detection, and medicine. Investigations on using aerogels as high surface area carriers for dispersing bimetallic nanoparticles are leading to development of new composite materials with outstanding properties due to the remarkable properties of aerogels. The review focuses on the techniques to synthesize these materials, their properties, the techniques to tune their pore properties and surface chemistry and the applications of these materials.